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NAPH

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inner space of mitochondria (matrix)

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What role do photosynthesis and cellular respiration play in the recycling of carbon?

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What role do photosynthesis and cellular respiration play in the recycling of carbon?

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While photosynthesis requires carbon dioxide and releases oxygen, cellular respiration requires oxygen and releases carbon dioxide. It is the released oxygen that is used by us and most other organisms for cellular respiration. ... The carboncycle is the pathways through which carbon is recycled in the biosphere.

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 How is energy transformed and matter utilized by living things?

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 How is energy transformed and matter utilized by living things?

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by using the energy cycle from the sun

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If cells can produce chemical energy in an anaerobic environment, why do we need oxygen?

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If cells can produce chemical energy in an anaerobic environment, why do we need oxygen?

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oxygen is needed because you cant live without it that all i know and thats all i need to know

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What role does photosynthesis play in altering Earth's atmosphere?

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What role does photosynthesis play in altering Earth's atmosphere?

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Photosynthesis plays an important role in the environment for several reasons as it helps clean the air because plants use the carbon dioxide in the air for photosynthesis, the plants produce oxygen as a by-product which all humans and animals need to live and it also makes plants grow, providing food for animals that feed on plants. Without plants, the world would quickly become uninhabitable for human and animal life. The oxygen would be used up and there would be no food to feed the animals that humans rely on for food.

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Photosynthesis plays an important role in the environment for several reasons as it helps clean the air because plants use the carbon dioxide in the air for photosynthesis, the plants produce oxygen as a by-product which all humans and animals need to live and it also makes plants grow, providing food for animals that feed on plants. Without plants, the world would quickly become uninhabitable for human and animal life. The oxygen would be used up and there would be no food to feed the animals that humans rely on for food.

The sugars that are in the plants that herbivores eat not only produce energy for the plant itself, but provide energy for the animal that eats it. Vegetables and other plants not only create sugars and carbohydrates for their own use, but also for the use of the consumers. Outside of the consumption of the organisms that use photosynthesis, many of them can be used for their fibers. Cotton is a good example of a plant that uses photosynthesis, but is used for the making of clothing instead of food. Algae also uses photosynthesis to create energy, though it lives in water unlike land plants. Algae provides food for a number of aquatic animals and puts oxygen into the water for ocean dwellers to use.

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How Does Photosynthesis Affect the Environment?

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Photosynthesis plays an important role in the environment for several reasons as it helps clean the air because plants use the carbon dioxide in the air for photosynthesis, the plants produce oxygen as a by-product which all humans and animals need to live and it also makes plants grow, providing food for animals that feed on plants.

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How are photosynthesis and Cellular Respiration related to one another in the biosphere?

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How are photosynthesis and Cellular Respiration related to one another in the biosphere?

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Photosynthesis makes the glucose that is used in cellular respiration to make ATP. The glucose is then turned back into carbon dioxide, which is used inphotosynthesis. While water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.

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Covers relationship between cellular respiration and photosynthesis.

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ANSWERS

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How do the products of photosynthesis become amino acids?

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How do the products of photosynthesis become amino acids?

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by mixing together their compounds and structure.

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Methods have been developed for performing dual tracer experiments with 15N and 14C on the photosynthesis and biosynthesis of amino acids in Chlorella...

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The structure of the major Biomolecules 

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The structure of the major Biomolecules 

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Bio molecules are compounds that center around the element, carbon.  Carbon, because of its valence structure, is actually quite versatile and probably responsible for the great variation of life on this planet.

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Biomolecules are compounds that center around the element, carbon. Carbon, because of its valence structure, is actually quite versatile and probably responsible for the great variation of life on this planet. In today's post we are going to look at the four major classes of biomolecules. For each class, pay special attention to the structure and function of these biomolecules.

Proteins make up the majority of biomolecules present in a cell. These molecules have enormous variation. Proteins are responsible for many enzymatic functions in the cell and play an important structural role . Proteins are composed of subunits called amino acids. There are 21 different types of amino acids (including the less known selenocysteine). It would be very important for the student to know the different functional groups that make up a single amino acid. Amino acids are composed of a carboxyl group and an amino group bound to a central carbon atom. A hydrogen atom occupies the third bonding site on the carbon and a variable "R" group occupies the fourth. This R group gives the amino acid special properties that are responsible for making proteins functional. Long chains of amino acids, formed by peptide bonds between each amino acid, form a polypeptide. More on protein structure can be found at this blog post.

Nucleic acids are the second type of biomolecules that we will discuss. These molecules are responsible for all of our genetic information. You are probably very familiar with Deoxyribo Nucleic Acid (DNA) and Ribo Nucleic Acid (RNA). Nucleic acids are formed from subunits called nucleotides. There are 5 different types of nucleotides in the cell; Adenine, Thymine, Guanine, Cytosine and Uracil. Each nucleotide is composed of a nitrogenous base, a 5-carbon sugar, and 3 phosphate groups. The bonds that form between nucleotides are called phosphodiester bonds. Nucleotides are responsible for more than just composing DNA and RNA, as ATP is a nucleotide and is also the energy currency of the cell! Click here for in-depth post dedicated to the structure of DNA.

Carbohydrates provide an energy source for the cell and also may play a structural role. The simplest subunit of a carbohydrate is a monosaccharide. The structure of the glucose molecule is a good representation of carbohydrate subunits, also called a monomer.

The final class of biomolecules are lipids. Lipids are composed of long hydrocarbon chains (-CH2-). These molecules hold an incredible amount of energy and are therefore energy storage molecules. Because of some pretty neat biochemical properties (hydrocarbons are hydrophobic), lipids are the major component of cell membranes. Cholesterol and other sterols are also types of lipids and are necessary components of cell membranes.

If your teacher drew these four molecules on an exam, would you be able to identify which is which?

Interested in science curriculum for your students (classroom and homeschool)? Head over to my curriculum store.

This entry was posted in Biochemistry, Biology, Molecular Biology. Bookmark the permalink.

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Biomolecules are compounds that center around the element, carbon. Carbon, because of its valence structure, is actually quite versatile and probably responsible for the great variation of life on this planet. In today's post we are going to look at the four major classes of biomolecules.

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CHON is a mnemonic acronym for the four most common elements in living organisms: carbon, hydrogen, oxygen, and nitrogen.

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The acronym CHNOPS, which stands for c arbon, h ydrogen, n itrogen, o xygen, p hosphorus, s ulfur, represents the six most important chemical elements whose covalent combinations make up most biological molecules on Earth. Most of the elements are nonmetals. Sulfur is contained in the amino acids cysteine and methionine.

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Proteins, Lipids, Carbohydrates, Nucleic Acids

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Proteins, Lipids, Carbohydrates, Nucleic Acids

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Proteins, Lipids, Carbohydrates, Nucleic Acids are the four major biomolecules

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A biomolecule or biological molecule is any molecule that is present in living organisms, including large macro molecules such as proteins, carbohydrates, lipids, and nucleic acids, as well as small molecules such as primary metabolites, secondary metabolites, and natural products.

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A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development. Biomolecules include large macromolecules (or polyanions) such as proteins, carbohydrates, lipids, and nucleic acids, as well as small molecules such as primary metabolites, secondary metabolites and natural products. A more general name for this class of material is biological materials. Biomolecules are an important element of living organisms, those biomolecules are often endogenous, produced within the organism but organisms usually need exogenous biomolecules, for example certain nutrients, to survive.

Biology and its subfields of biochemistry and molecular biology study biomolecules and their reactions. Most biomolecules are organic compounds, and just four elements- oxygen, carbon, hydrogen, and nitrogen-make up 96% of the human body's mass. But many other elements, such as the various biometals, are also present in small amounts.

The uniformity of both specific types of molecules (the biomolecules) and of certain metabolic pathways are invariant features among the wide diversity of life forms; thus these biomolecules and metabolic pathways are referred to as "biochemical universals" or "theory of material unity of the living beings", a unifying concept in biology, along with cell theory and evolution theory.

A diverse range of biomolecules exist, including:

Nucleosides are molecules formed by attaching a nucleobase to a ribose or deoxyribose ring. Examples of these include cytidine (C), uridine (U), adenosine (A), guanosine (G), and thymidine (T).

Nucleosides can be phosphorylated by specific kinases in the cell, producing nucleotides. Both DNA and RNA are polymers, consisting of long, linear molecules assembled by polymerase enzymes from repeating structural units, or monomers, of mononucleotides. DNA uses the deoxynucleotides C, G, A, and T, while RNA uses the ribonucleotides (which have an extra hydroxyl(OH) group on the pentose ring) C, G, A, and U. Modified bases are fairly common (such as with methyl groups on the base ring), as found in ribosomal RNA or transfer RNAs or for discriminating the new from old strands of DNA after replication.

Each nucleotide is made of an acyclic nitrogenous base, a pentose and one to three phosphate groups. They contain carbon, nitrogen, oxygen, hydrogen and phosphorus. They serve as sources of chemical energy ( adenosine triphosphate and guanosine triphosphate), participate in cellular signaling ( cyclic guanosine monophosphate and cyclic adenosine monophosphate), and are incorporated into important cofactors of enzymatic reactions ( coenzyme A, flavin adenine dinucleotide, flavin mononucleotide, and nicotinamide adenine dinucleotide phosphate).

DNA and RNA structure

DNA structure is dominated by the well-known double helix formed by Watson-Crick base-pairing of C with G and A with T. This is known as B-form DNA, and is overwhelmingly the most favorable and common state of DNA; its highly specific and stable base-pairing is the basis of reliable genetic information storage. DNA can sometimes occur as single strands (often needing to be stabilized by single-strand binding proteins) or as A-form or Z-form helices, and occasionally in more complex 3D structures such as the crossover at Holliday junctions during DNA replication.

RNA, in contrast, forms large and complex 3D tertiary structures reminiscent of proteins, as well as the loose single strands with locally folded regions that constitute messenger RNA molecules. Those RNA structures contain many stretches of A-form double helix, connected into definite 3D arrangements by single-stranded loops, bulges, and junctions. Examples are tRNA, ribosomes, ribozymes, and riboswitches. These complex structures are facilitated by the fact that RNA backbone has less local flexibility than DNA but a large set of distinct conformations, apparently because of both positive and negative interactions of the extra OH on the ribose. Structured RNA molecules can do highly specific binding of other molecules and can themselves be recognized specifically; in addition, they can perform enzymatic catalysis (when they are known as " ribozymes", as initially discovered by Tom Cech and colleagues).

Monosaccharides are the simplest form of carbohydrates with only one simple sugar. They essentially contain an aldehyde or ketone group in their structure. The presence of an aldehyde group in a monosaccharide is indicated by the prefix aldo-. Similarly, a ketone group is denoted by the prefix keto-. Examples of monosaccharides are the hexoses, glucose, fructose, Trioses, Tetroses, Heptoses, galactose, pentoses, ribose, and deoxyribose. Consumed fructose and glucose have different rates of gastric emptying, are differentially absorbed and have different metabolic fates, providing multiple opportunities for 2 different saccharides to differentially affect food intake. Most saccharides eventually provide fuel for cellular respiration.

Disaccharides are formed when two monosaccharides, or two single simple sugars, form a bond with removal of water. They can be hydrolyzed to yield their saccharin building blocks by boiling with dilute acid or reacting them with appropriate enzymes. Examples of disaccharides include sucrose, maltose, and lactose.

Polysaccharides are polymerized monosaccharides, or complex carbohydrates. They have multiple simple sugars. Examples are starch, cellulose, and glycogen. They are generally large and often have a complex branched connectivity. Because of their size, polysaccharides are not water-soluble, but their many hydroxy groups become hydrated individually when exposed to water, and some polysaccharides form thick colloidal dispersions when heated in water. Shorter polysaccharides, with 3 - 10 monomers, are called oligosaccharides. A fluorescent indicator-displacement molecular imprinting sensor was developed for discriminating saccharides. It successfully discriminated three brands of orange juice beverage. The change in fluorescence intensity of the sensing films resulting is directly related to the saccharide concentration.

Lignin is a complex polyphenolic macromolecule composed mainly of beta-O4-aryl linkages. After cellulose, lignin is the second most abundant biopolymer and is one of the primary structural components of most plants. It contains subunits derived from p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol and is unusual among biomolecules in that it is racemic. The lack of optical activity is due to the polymerization of lignin which occurs via free radical coupling reactions in which there is no preference for either configuration at a chiral center.

Lipids (oleaginous) are chiefly , and are the basic building blocks of biological membranes. Another biological role is energy storage (e.g., triglycerides). Most lipids consist of a polar or hydrophilic head (typically glycerol) and one to three non polar or hydrophobic fatty acid tails, and therefore they are amphiphilic. Fatty acids consist of unbranched chains of carbon atoms that are connected by single bonds alone ( fatty acids) or by both single and double bonds (unsaturated fatty acids). The chains are usually 14-24 carbon groups long, but it is always an even number.

For lipids present in biological membranes, the hydrophilic head is from one of three classes:

Glycolipids, whose heads contain an oligosaccharide with 1-15 saccharide residues.

Phospholipids, whose heads contain a positively charged group that is linked to the tail by a negatively charged phosphate group.

Sterols, whose heads contain a planar steroid ring, for example, cholesterol.

Other lipids include prostaglandins and leukotrienes which are both 20-carbon fatty acyl units synthesized from arachidonic acid. They are also known as fatty acids

Amino acids contain both amino and carboxylic acid functional groups. (In biochemistry, the term amino acid is used when referring to those amino acids in which the amino and carboxylate functionalities are attached to the same carbon, plus proline which is not actually an amino acid).

Modified amino acids are sometimes observed in proteins; this is usually the result of enzymatic modification after translation ( protein synthesis). For example, phosphorylation of serine by kinases and dephosphorylation by phosphatases is an important control mechanism in the cell cycle. Only two amino acids other than the standard twenty are known to be incorporated into proteins during translation, in certain organisms:

Besides those used in protein synthesis, other biologically important amino acids include carnitine (used in lipid transport within a cell), ornithine, GABA and taurine.

Protein structure

The particular series of amino acids that form a protein is known as that protein's primary structure. This sequence is determined by the genetic makeup of the individual. It specifies the order of side-chain groups along the linear polypeptide "backbone".

Proteins have two types of well-classified, frequently occurring elements of local structure defined by a particular pattern of hydrogen bonds along the backbone: alpha helix and beta sheet. Their number and arrangement is called the secondary structure of the protein. Alpha helices are regular spirals stabilized by hydrogen bonds between the backbone CO group ( carbonyl) of one amino acid residue and the backbone NH group ( amide) of the i+4 residue. The spiral has about 3.6 amino acids per turn, and the amino acid side chains stick out from the cylinder of the helix. Beta pleated sheets are formed by backbone hydrogen bonds between individual beta strands each of which is in an "extended", or fully stretched-out, conformation. The strands may lie parallel or antiparallel to each other, and the side-chain direction alternates above and below the sheet. Hemoglobin contains only helices, natural silk is formed of beta pleated sheets, and many enzymes have a pattern of alternating helices and beta-strands. The secondary-structure elements are connected by "loop" or "coil" regions of non-repetitive conformation, which are sometimes quite mobile or disordered but usually adopt a well-defined, stable arrangement.

The overall, compact, 3D structure of a protein is termed its tertiary structure or its "fold". It is formed as result of various attractive forces like hydrogen bonding, disulfide bridges, hydrophobic interactions, hydrophilic interactions, van der Waals force etc.

When two or more polypeptide chains (either of identical or of different sequence) cluster to form a protein, quaternary structure of protein is formed. Quaternary structure is an attribute of polymeric (same-sequence chains) or heteromeric (different-sequence chains) proteins like hemoglobin, which consists of two "alpha" and two "beta" polypeptide chains.

Apoenzymes

An apoenzyme (or, generally, an apoprotein) is the protein without any small-molecule cofactors, substrates, or inhibitors bound. It is often important as an inactive storage, transport, or secretory form of a protein. This is required, for instance, to protect the secretory cell from the activity of that protein. Apoenzymes become active enzymes on addition of a cofactor. Cofactors can be either inorganic (e.g., metal ions and iron-sulfur clusters) or organic compounds, (e.g., [Flavin group|flavin] and heme). Organic cofactors can be either prosthetic groups, which are tightly bound to an enzyme, or coenzymes, which are released from the enzyme's active site during the reaction.

Isoenzymes

Isoenzymes, or isozymes, are multiple forms of an enzyme, with slightly different protein sequence and closely similar but usually not identical functions. They are either products of different genes, or else different products of alternative splicing. They may either be produced in different organs or cell types to perform the same function, or several isoenzymes may be produced in the same cell type under differential regulation to suit the needs of changing development or environment. LDH ( lactate dehydrogenase) has multiple isozymes, while fetal hemoglobin is an example of a developmentally regulated isoform of a non-enzymatic protein. The relative levels of isoenzymes in blood can be used to diagnose problems in the organ of secretion .

1. Bunge, M. (1979). ^ Treatise on Basic Philosophy, vol. 4. Ontology II: A World of Systems, p. 61-2. link.

2. ^ Voon, C. H.; Sam, S. T. (2019). "2.1 Biosensors". Nanobiosensors for Biomolecular Targeting. Elsevier. ISBN 978-0-12-813900-4.

3. ^ endogeny. (2011) Segen's Medical Dictionary. The Free Dictionary by Farlex. Farlex, Inc. Accessed June 27, 2019.

4. ^ Green, D. E.; Goldberger, R. (1967). Molecular Insights into the Living Process. New York: Academic Press - via Google Books.

5. ^ Gayon, J. (1998). "La philosophie et la biologie". In Mattéi, J. F. (ed.). Encyclopédie philosophique universelle. vol. IV, Le Discours philosophique. Presses Universitaires de France. pp. 2152-2171. ISBN 9782130448631 - via Google Books.

6. ^ Slabaugh, Michael R. & Seager, Spencer L. (2007). Organic and Biochemistry for Today (6th ed.). Pacific Grove: Brooks Cole. ISBN 978-0-495-11280-8.

7. ^ Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Wlater P (2002). Molecular biology of the cell (4th ed.). New York: Garland Science. pp. 120-1. ISBN 0-8153-3218-1.

8. ^ Richardson JS, Schneider B, Murray LW, Kapral GJ, Immormino RM, Headd JJ, Richardson DC, Ham D, Hershkovits E, Williams LD, Keating KS, Pyle AM, Micallef D, Westbrook J, Berman HM (2008). "RNA Backbone: Consensus all-angle conformers and modular string nomenclature". RNA. 14 (3): 465-481. doi:10.1261/rna.657708. PMC . PMID 18192612.

9. ^ Kruger K, Grabowski PJ, Zaug AJ, Sands J, Gottschling DE, Cech TR (1982). "Self-splicing RNA: autoexcision and autocyclization of the ribosomal RNA intervening sequence of Tetrahymena". Cell. 31 (1): 147-157. doi:10.1016/0092-8674(82)90414-7. PMID 6297745. S2CID 14787080.

10. ^ Peng, Bo & Yu Qin (June 2009). "Fructose and Satiety". Journal of Nutrition: 6137-42.

11. ^ Jin, Tan; Wang He-Fang & Yan Xiu-Ping (2009). "Discrimination of Saccharides with a Fluorescent Molecular Imprinting Sensor Array Based on Phenylboronic Acid Functionalized Mesoporous Silica". Anal. Chem. 81 (13): 5273-80. doi:10.1021/ac900484x. PMID 19507843.

12. ^ Bo Peng & Yu Qin (2008). "Lipophilic Polymer Membrane Optical Sensor with a Synthetic Receptor for Saccharide Detection". Anal. Chem. 80 (15): 6137-41. doi:10.1021/ac800946p. PMID 18593197.

13. ^ K. Freudenberg; A.C. Nash, eds. (1968). Constitution and Biosynthesis of Lignin. Berlin: Springer-Verlag.

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A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development. Biomolecules include large macromolecules (or polyanions) such as proteins, carbohydrates, lipids, and nucleic acids, as well as small molecules such as primary metabolites, secondary metabolites and natural products.

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Amount of energy that is available at each level 

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Amount of energy that is available at each level 

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trophic level: energy flow and trophic levels. The amount of energy at each trophic level decreases as it moves through an ecosystem. As little as 10 percent of the energy at any trophiclevel is transferred to the next level; the rest is lost largely through metabolic processes as heat.

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The amount of energy at each trophic level decreases as it moves through an ecosystem. As little as 10 percent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat. If a grassland ecosystem has 10,000 kilocalories (kcal) of…

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an organism, especially a soil bacterium, fungus, or invertebrate, that decomposes organic material.

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Herbivores are those animals, such as deer and koalas, that only eat plant material
Omnivores are those animals, such as bears and humans, that can eat a variety of food sources, but tend to prefer one type to another.

While most carnivores, such as cats, eat only meat, facultative carnivores, such as dogs, behave more like omnivores as they can eat plant matter along with meat.

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A heterotroph is known as a consumer in the food chain. Consumers are organisms that cannot make their own food supply. They use the food that producers make, or they eat other organisms. Animals are consumers.

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Heterotroph - Simple English Wikipedia, the free encyclopedia

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A heterotroph is known as a consumer in the food chain. Consumers are organisms that cannot make their own food supply. They use the food that producers make, or they eat other organisms. Animals are consumers. To stay alive, consumers must get food from other organisms. There are three types of consumers:Herbivores, Carnivores, and Omnivores.

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An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. Because autotrophs produce their own food, they are sometimes called producers. Plants are the most familiar type of autotroph, but there are many different kinds of autotrophic organisms.

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An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. Because autotrophs produce their own food, they are sometimes called producers.

Plants are the most familiar type of autotroph, but there are many different kinds of autotrophic organisms. Algae, which live in water and whose larger forms are known as seaweed, is autotrophic. Phytoplankton, tiny organisms that live in the ocean, are autotrophs. Some types of bacteria are autotrophs.

Most autotrophs use a process called photosynthesis to make their food. In photosynthesis, autotrophs use energy from the sun to convert water from the soil and carbon dioxide from the air into a nutrient called glucose. Glucose is a type of sugar. The glucose gives plants energy. Plants also use glucose to make cellulose, a substance they use to grow and build cell walls.

All plants with green leaves, from the tiniest mosses to towering fir trees, synthesize, or create, their own food through photosynthesis. Algae, phytoplankton, and some bacteria also perform photosynthesis.

Some rare autotrophs produce food through a process called chemosynthesis, rather than through photosynthesis. Autotrophs that perform chemosynthesis do not use energy from the sun to produce food. Instead, they make food using energy from chemical reactions, often combining hydrogen sulfide or methane with oxygen.

Organisms that use chemosynthesis live in extreme environments, where the toxic chemicals needed for oxidation are found. For example, bacteria living in active volcanoes oxidize sulfur to produce their own food. At Yellowstone National Park in the U.S. states of Wyoming, Idaho, and Montana, bacteria capable of chemosynthesis have been found in hot springs.

Bacteria that live in the deep ocean, near hydrothermal vents, also produce food through chemosynthesis. A hydrothermal vent is a narrow crack in the seafloor. Seawater seeps down through the crack into hot, partly melted rock below. The boiling-hot water then circulates back up into the ocean, loaded with minerals from the hot rock. These minerals include hydrogen sulfide, which the bacteria use in chemosynthesis.

Autotrophic bacteria that produce food through chemosynthesis have also been found at places on the seafloor called cold seeps. At cold seeps, hydrogen sulfide and methane seep up from beneath the seafloor and mix with the ocean water and dissolved carbon dioxide. The autotrophic bacteria oxidize these chemicals to produce energy.

Autotrophs in the Food Chain

To explain a food chain-a description of which organisms eat which other organisms in the wild-scientists group organisms into trophic, or nutritional, levels. There are three trophic levels. Because autotrophs do not consume other organisms, they are the first trophic level.

Autotrophs are eaten by herbivores, organisms that consume plants. Herbivores are the second trophic level. Carnivores, creatures that eat meat, and omnivores, creatures that eat all types of organisms, are the third trophic level.

Herbivores, carnivores, and omnivores are all consumers-they consume nutrients rather than making their own. Herbivores are primary consumers. Carnivores and omnivores are secondary consumers.

All food chains start with some type of autotroph (producer). For example, autotrophs such as grasses grow in the Rocky Mountains. Mule deer are herbivores (primary consumers), which feed on the autotrophic grasses. Carnivores (secondary consumers) such as mountain lions hunt and consume the deer.

In hydrothermal vents, the food chain's producer is autotrophic bacteria. Primary consumers such as snails and mussels consume the autotrophs. Carnivores such as octopus consume the snails and mussels.

An increase in the number of autotrophs will usually lead to an increase in the number of animals that eat them. However, a decrease in the number and variety of autotrophs in an area can devastate the entire food chain. If a wooded area burns in a forest fire or is cleared to build a shopping mall, herbivores such as rabbits can no longer find food. Some of the rabbits may move to a better habitat, and some may die. Without the rabbits, fox es and other meat-eaters that feed on them also lose their food source. They, too, must move to survive.

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An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. Because autotrophs produce their own food, they are sometimes called producers. Plants are the most familiar type of autotroph, but there are many different kinds of autotrophic organisms. Algae, which live in water and whose larger forms are known as seaweed, is autotrophic.

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The low rate of energy transfer between trophic levels makes decomposers generally more important than producers in terms of energy flow. Decomposers process large amounts of organic material and return nutrients to the ecosystem in inorganic form, which are then taken up again by primary producers.

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The Habitable Planet Unit 4 - Ecosystems // Online Textbook

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The low rate of energy transfer between trophic levels makes decomposers generally more important than producers in terms of energy flow. Decomposers process large amounts of organic material and return nutrients to the ecosystem in inorganic form, which are then taken up again by primary producers.

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An energy pyramid is a graphical model of energy flowin a community. The different levels represent different groups of organisms that might compose a food chain. From the bottom-up, they are as follows: Producers — bring energy from nonliving sources into the community.

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Global Warming Potential (100-year): 1. Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities. In 2014, CO2 accounted for about 80.9% of all U.S. greenhouse gas emissions from human activities.

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Products of Photosynthesis = Reactants of Cellular Respiration 

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Products of Photosynthesis = Reactants of Cellular Respiration 

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Most of the steps of cellular respiration take place in the mitochondria. Oxygen and glucose are both reactants in the process of cellular respiration. The main productof cellular respiration is ATP; waste products include carbon dioxide and water.

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Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products.

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Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from oxygen molecules or nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy because weak high-energy bonds, in particular in molecular oxygen, are replaced by stronger bonds in the products. Respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. The overall reaction occurs in a series of biochemical steps, some of which are redox reactions. Although cellular respiration is technically a combustion reaction, it clearly does not resemble one when it occurs in a living cell because of the slow, controlled release of energy from the series of reactions.

Nutrients that are commonly used by animal and plant cells in respiration include sugar, amino acids and fatty acids, and the most common oxidizing agent providing most of the chemical energy is molecular oxygen (O ₂). The chemical energy stored in ATP (the bond of its third phosphate group to the rest of the molecule can be broken allowing more stable products to form, thereby releasing energy for use by the cell) can then be used to drive processes requiring energy, including biosynthesis, locomotion or transport of molecules across cell membranes.

Aerobic respiration

Aerobic respiration requires oxygen (O ₂) in order to create ATP. Although carbohydrates, fats, and proteins are consumed as reactants, aerobic respiration is the preferred method of pyruvate breakdown in glycolysis, and requires pyruvate to the mitochondria in order to be fully oxidized by the citric acid cycle. The products of this process are carbon dioxide and water, and the energy transferred is used to break bonds in ADP to add a third phosphate group to form ATP ( adenosine triphosphate), by substrate-level phosphorylation, NADH and

The negative ΔG indicates that the reaction can occur spontaneously.

The potential of NADH and FADH ₂ is converted to more ATP through an electron transport chain with oxygen and protons (hydrogen) as the "terminal electron acceptors". Most of the ATP produced by aerobic cellular respiration is made by oxidative phosphorylation. The energy of O ₂ released is used to create a chemiosmotic potential by pumping protons across a membrane. This potential is then used to drive ATP synthase and produce ATP from ADP and a phosphate group. Biology textbooks often state that 38 ATP molecules can be made per oxidized glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 34 from the electron transport system). However, this maximum yield is never quite reached because of losses due to leaky membranes as well as the cost of moving pyruvate and ADP into the mitochondrial matrix, and current estimates range around 29 to 30 ATP per glucose.

Aerobic metabolism is up to 15 times more efficient than anaerobic metabolism (which yields 2 molecules ATP per 1 molecule glucose) because the double bond in O ₂ is of higher energy than other double bonds or pairs of single bonds in other common molecules in the biosphere. However, some anaerobic organisms, such as methanogens are able to continue with anaerobic respiration, yielding more ATP by using other inorganic molecules (not oxygen) of high energy as final electron acceptors in the electron transport chain. They share the initial pathway of glycolysis but aerobic metabolism continues with the Krebs cycle and oxidative phosphorylation. The post-glycolytic reactions take place in the mitochondria in eukaryotic cells, and in the cytoplasm in prokaryotic cells.

Glycolysis

Glycolysis is a metabolic pathway that takes place in the cytosol of cells in all living organisms. Glycolysis can be literally translated as "sugar splitting", and occurs with or without the presence of oxygen. In aerobic conditions, the process converts one molecule of glucose into two molecules of pyruvate (pyruvic acid), generating energy in the form of two net molecules of ATP. Four molecules of ATP per glucose are actually produced, but two are consumed as part of the preparatory phase. The initial phosphorylation of glucose is required to increase the reactivity (decrease its stability) in order for the molecule to be cleaved into two pyruvate molecules by the enzyme aldolase. During the pay-off phase of glycolysis, four phosphate groups are transferred to ADP by substrate-level phosphorylation to make four ATP, and two NADH are produced when the pyruvate is oxidized. The overall reaction can be expressed this way:

Starting with glucose, 1 ATP is used to donate a phosphate to glucose to produce glucose 6-phosphate. Glycogen can be converted into glucose 6-phosphate as well with the help of glycogen phosphorylase. During energy metabolism, glucose 6-phosphate becomes fructose 6-phosphate. An additional ATP is used to phosphorylate fructose 6-phosphate into fructose 1,6-bisphosphate by the help of phosphofructokinase. Fructose 1,6-biphosphate then splits into two phosphorylated molecules with three carbon chains which later degrades into pyruvate.

Oxidative decarboxylation of pyruvate

Pyruvate is oxidized to acetyl-CoA and CO ₂ by the pyruvate dehydrogenase complex (PDC). The PDC contains multiple copies of three enzymes and is located in the mitochondria of eukaryotic cells and in the cytosol of prokaryotes. In the conversion of pyruvate to acetyl-CoA, one molecule of NADH and one molecule of CO ₂ is formed.

Citric acid cycle

This is also called the Krebs cycle or the tricarboxylic acid cycle. When oxygen is present, acetyl-CoA is produced from the pyruvate molecules created from glycolysis. Once acetyl-CoA is formed, aerobic or anaerobic respiration can occur. When oxygen is present, the mitochondria will undergo aerobic respiration which leads to the Krebs cycle. However, if oxygen is not present, fermentation of the pyruvate molecule will occur. In the presence of oxygen, when acetyl-CoA is produced, the molecule then enters the citric acid cycle (Krebs cycle) inside the mitochondrial matrix, and is oxidized to while at the same time reducing NAD to NADH. NADH can be used by the electron transport chain to create further ATP as part of oxidative phosphorylation. To fully oxidize the equivalent of one glucose molecule, two acetyl-CoA must be metabolized by the Krebs cycle. Two low-energy waste products, H ₂O and CO ₂, are created during this cycle.

The citric acid cycle is an 8-step process involving 18 different enzymes and co-enzymes. During the cycle, acetyl-CoA (2 carbons) + oxaloacetate (4 carbons) yields citrate (6 carbons), which is rearranged to a more reactive form called isocitrate (6 carbons). Isocitrate is modified to become α-ketoglutarate (5 carbons), succinyl-CoA, succinate, fumarate, malate, and, finally, oxaloacetate.

The net gain from one cycle is 3 NADH and 1 FADH ₂ as hydrogen- (proton plus electron)-carrying compounds and 1 high-energy GTP, which may subsequently be used to produce ATP. Thus, the total yield from 1 glucose molecule (2 pyruvate molecules) is 6 NADH, 2 FADH ₂, and 2 ATP.

Oxidative phosphorylation

In eukaryotes, oxidative phosphorylation occurs in the mitochondrial cristae. It comprises the electron transport chain that establishes a proton gradient (chemiosmotic potential) across the boundary of the inner membrane by oxidizing the NADH produced from the Krebs cycle. ATP is synthesized by the ATP synthase enzyme when the chemiosmotic gradient is used to drive the phosphorylation of ADP. The electron transfer is driven by the chemical energy of exogenous oxygen and, with the addition of two protons, water is formed.

Efficiency of ATP production

The table below describes the reactions involved when one glucose molecule is fully oxidized into carbon dioxide. It is assumed that all the reduced coenzymes are oxidized by the electron transport chain and used for oxidative phosphorylation.

Glycolysis preparatory phase

−2

Phosphorylation of glucose and fructose 6-phosphate uses two ATP from the cytoplasm.

Glycolysis pay-off phase

4

Substrate-level phosphorylation

2 NADH

3 or 5

Oxidative phosphorylation : Each NADH produces net 1.5 ATP (instead of usual 2.5) due to NADH transport over the mitochondrial membrane

Oxidative decarboxylation of pyruvate

2 NADH

5

Oxidative phosphorylation

Krebs cycle

2

Substrate-level phosphorylation

6 NADH

15

Oxidative phosphorylation

Total yield

30 or 32 ATP

From the complete oxidation of one glucose molecule to carbon dioxide and oxidation of all the reduced coenzymes.

Although there is a theoretical yield of 38 ATP molecules per glucose during cellular respiration, such conditions are generally not realized because of losses such as the cost of moving pyruvate (from glycolysis), phosphate, and ADP (substrates for ATP synthesis) into the mitochondria. All are actively transported using carriers that utilize the stored energy in the proton electrochemical gradient.

Pyruvate is taken up by a specific, low K m transporter to bring it into the mitochondrial matrix for oxidation by the pyruvate dehydrogenase complex.

The phosphate carrier (PiC) mediates the electroneutral exchange (antiport) of phosphate (H₂PO₄−; Pi) for OH− or symport of phosphate and protons (H⁺) across the inner membrane, and the driving force for moving phosphate ions into the mitochondria is the proton motive force.

The ATP-ADP translocase (also called adenine nucleotide translocase, ANT) is an antiporter and exchanges ADP and ATP across the inner membrane. The driving force is due to the ATP (−4) having a more negative charge than the ADP (−3), and thus it dissipates some of the electrical component of the proton electrochemical gradient.

The outcome of these transport processes using the proton electrochemical gradient is that more than 3 H⁺ are needed to make 1 ATP. Obviously, this reduces the theoretical efficiency of the whole process and the likely maximum is closer to 28-30 ATP molecules. In practice the efficiency may be even lower because the inner membrane of the mitochondria is slightly leaky to protons. Other factors may also dissipate the proton gradient creating an apparently leaky mitochondria. An uncoupling protein known as thermogenin is expressed in some cell types and is a channel that can transport protons. When this protein is active in the inner membrane it short circuits the coupling between the electron transport chain and ATP synthesis. The potential energy from the proton gradient is not used to make ATP but generates heat. This is particularly important in brown fat thermogenesis of newborn and hibernating mammals.

According to some newer sources, the ATP yield during aerobic respiration is not 36-38, but only about 30-32 ATP molecules / 1 molecule of glucose , because:

ATP : NADH+H⁺ coming from glycolysis ratio during the oxidative phosphorylation is

1.5, as for FADH₂, if hydrogen atoms (2H⁺+2e−) are transferred from cytosolic NADH+H⁺ to mitochondrial FAD by the glycerol phosphate shuttle located in the inner mitochondrial membrane.

2.5 in case of malate-aspartate shuttle transferring hydrogen atoms from cytosolic NADH+H⁺ to mitochondrial NAD⁺

So finally we have, per molecule of glucose

Altogether this gives 4 + 3 (or 5) + 20 + 3 = 30 (or 32) ATP per molecule of glucose

These figures may still require further tweaking as new structural details become available. The above value of 3 H+/ATP for the synthase assumes that the synthase translocates 9 protons, and produces 3 ATP, per rotation. The number of protons depends on the number of c subunits in the Fo c-ring, and it is now known that this is 10 in yeast Fo and 8 for vertebrates. Including one H⁺ for the transport reactions, this means that synthesis of one ATP requires 1+10/3=4.33 protons in yeast and 1+8/3 = 3.67 in vertebrates. This would imply that in human mitochondria the 10 protons from oxidizing NADH would produce 2.72 ATP (instead of 2.5) and the 6 protons from oxidizing succinate or ubiquinol would produce 1.64 ATP (instead of 1.5). This is consistent with experimental results within the margin of error described in a recent review.

The total ATP yield in ethanol or lactic acid fermentation is only 2 molecules coming from glycolysis, because pyruvate is not transferred to the mitochondrion and finally oxidized to the carbon dioxide (CO ₂), but reduced to ethanol or lactic acid in the cytoplasm.

Fermentation

Without oxygen, pyruvate ( pyruvic acid) is not metabolized by cellular respiration but undergoes a process of fermentation. The pyruvate is not transported into the mitochondrion but remains in the cytoplasm, where it is converted to waste products that may be removed from the cell. This serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. Fermentation oxidizes NADH to NAD⁺ so it can be re-used in glycolysis. In the absence of oxygen, fermentation prevents the buildup of NADH in the cytoplasm and provides NAD⁺ for glycolysis. This waste product varies depending on the organism. In skeletal muscles, the waste product is lactic acid. This type of fermentation is called lactic acid fermentation. In strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by NADH. During anaerobic glycolysis, NAD⁺ regenerates when pairs of hydrogen combine with pyruvate to form lactate. Lactate formation is catalyzed by lactate dehydrogenase in a reversible reaction. Lactate can also be used as an indirect precursor for liver glycogen. During recovery, when oxygen becomes available, NAD⁺ attaches to hydrogen from lactate to form ATP. In yeast, the waste products are ethanol and carbon dioxide. This type of fermentation is known as alcoholic or ethanol fermentation. The ATP generated in this process is made by substrate-level phosphorylation, which does not require oxygen.

Fermentation is less efficient at using the energy from glucose: only 2 ATP are produced per glucose, compared to the 38 ATP per glucose nominally produced by aerobic respiration. This is because most of the energy of aerobic respiration derives from O ₂ with its relatively weak, high-energy double bond. Glycolytic ATP, however, is created more quickly. For prokaryotes to continue a rapid growth rate when they are shifted from an aerobic environment to an anaerobic environment, they must increase the rate of the glycolytic reactions. For multicellular organisms, during short bursts of strenuous activity, muscle cells use fermentation to supplement the ATP production from the slower aerobic respiration, so fermentation may be used by a cell even before the oxygen levels are depleted, as is the case in sports that do not require athletes to pace themselves, such as sprinting.

Anaerobic respiration

Cellular respiration is the process by which biological fuels are oxidised in the presence of a high-energy inorganic electron acceptor (such as oxygen) to produce large amounts of energy, to drive the bulk production of ATP.

Anaerobic respiration is used by some microorganisms in which neither oxygen (aerobic respiration) nor pyruvate derivatives (fermentation) is the high-energy final electron acceptor. Rather, an inorganic acceptor such as sulfate (SO ₄ ²⁻), nitrate (NO ₃⁻), or sulfur (S) is used. Such organisms are typically found in unusual places such as underwater caves or near hydrothermal vents at the bottom of the ocean.

In July 2019, a scientific study of Kidd Mine in Canada discovered sulfur-breathing organisms which live 7900 feet below the surface, and which breathe sulfur in order to survive. These organisms are also remarkable due to consuming minerals such as pyrite as their food source.

References

External links

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Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert chemical energy from oxygen molecules or nutrients into adenosine triphosphate (ATP), and then release waste products.

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the series of processes by which carbon compounds are interconverted in the environment, chiefly involving the incorporation of carbon dioxide into living tissue by photosynthesis and its return to the atmosphere through respiration, the decay of dead organisms, and the burning of fossil fuels.

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For the thermonuclear reaction involving carbon that powers some stars, see CNO cycle. For organic chemical ring-shaped structures, see Cyclic compound. For the geochemical cycle, see Carbonate–silicate cycle.

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The c stands for the speed of light, a universal constant, so the whole equation breaks down to this: Energy is equal to matter multiplied by the speed of light squared. ... The reason is that kinetic energy, or the energy of motion, is proportional to mass.

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Einstein's equation E=mc² pops up on everything from baseball caps to bumper stickers. It's even the title of a 2008 Mariah Carey album. But what does Albert Einstein's famous equation really mean?

For starters, the E stands for energy and the m stands for mass, a measurement of the quantity of matter. Energy and matter are interchangeable. Furthermore, it's essential to remember that there's a set amount of energy/matter in the universe.

If you've ever read Dr. Seuss's children's book "The Sneetches," you probably remember how the yellow, birdlike characters in the story go through a machine to change back and forth between "star-bellied sneetches" and "plain-bellied sneetches." The number of sneetches remains constant throughout the story, but the ratio between plain- and star-bellied ones changes. It's the same way with energy and matter. The grand total remains constant, but energy regularly changes form into matter and matter into energy.

Now we're getting to the c² part of the equation, which serves the same purpose as the star-on and star-off machines in "The Sneetches." The c stands for the speed of light, a universal constant, so the whole equation breaks down to this: Energy is equal to matter multiplied by the speed of light squared.

Why would you need to multiply matter by the speed of light to produce energy? The reason is that energy, be it light waves or radiation, travels at the speed of light. That breaks down to 186,000 miles per second (300,000 kilometers per second). When we split an atom inside a nuclear power plant or an atomic bomb, the resulting energy releases at the speed of light.

But why is the speed of light squared? The reason is that kinetic energy, or the energy of motion, is proportional to mass. When you accelerate an object, the kinetic energy increases to the tune of the speed squared. You'll find an excellent example of this in any driver's education manual: If you double your speed, the braking distance is four times longer, so the braking distance is equal to the speed squared [source: UNSW Physics: Einsteinlight].

The speed of light squared is a colossal number, illustrating just how much energy there is in even tiny amounts of matter. A common example of this is that 1 gram of water -- if its whole mass were converted into pure energy via E=mc² -- contains as much energy as 20,000 tons (18,143 metric tons) of TNT exploding. That's why such a small amount of uranium or plutonium can produce such a massive atomic explosion.

Einstein's equation opened the door for numerous technological advances, from nuclear power and nuclear medicine to the inner workings of the sun. It shows us that matter and energy are one.

Explore the links below to learn even more about Einstein's theories.

Related Articles

More Great Links

Sources

"E = mc²: What does it mean, and where did the equation come from?" UNSW Physics: Einsteinlight. (Sept. 3, 2010)http://www.phys.unsw.edu.au/einsteinlight/jw/module5_equations.htm

Fowler, Michael. "Special Relativity." Galileo and Einstein. March 3, 2008. (Sept. 2, 2010)http://galileoandeinstein.physics.virginia.edu/lectures/spec_rel.html

"Gravitational Lensing: Astronomers Harness Einstein's Telescope." Science Daily. Feb. 24, 2009. (Aug. 9, 2010)http://www.sciencedaily.com/releases/2009/02/090220172053.htm

Knierim, Thomas. "Relativity." The Big View. June 10, 2010. (Sept. 2, 2010)http://www.thebigview.com/spacetime/relativity.html

Lightman, Alan. "Relativity and the Cosmos." NOVA. June 2005. (Sept. 2, 2010)http://www.pbs.org/wgbh/nova/einstein/relativity/

Lipson, Edward. "Lecture 17: Special Relativity." Syracuse University. (July 14, 2010)http://physics.syr.edu/courses/PHY106/Slides/PPT/Lec17-Special-Relativity_2.pdf

"Relativity." Worldbook at NASA. Nov. 29, 2007. (Sept. 2, 2010)http://www.nasa.gov/worldbook/relativity_worldbook.html

Ryden, Barbara. "Special Relativity." Ohio State University Department of Astronomy. Feb. 10, 2003. (Sept. 2, 2010)http://www.astronomy.ohio-state.edu/~ryden/ast162_6/notes23.html

Tyson, Peter. "The legacy of E = mc²." NOVA. June 2005. (Sept. 3, 2010)http://www.pbs.org/wgbh/nova/einstein/legacy.html

Whitlock, Laura and Tim Kallman. "What does E=mc² mean?" NASA: Ask a Physicist? Dec. 1, 2005. (Sept. 3, 2010)

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What does Einstein's famous equation really mean?

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It opened the door for numerous technological advances, from nuclear power and nuclear medicine to the inner workings of the sun. It even appeared in the title of a Mariah Carey album. Really. Can you define those three key variables, too?

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Law of Conservation of Mass-Energy (E=MC^2)

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Law of Conservation of Mass-Energy (E=MC^2)

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Conservation of mass and energy. Mass and energy can be seen as two names (and two measurement units) for the same underlying, conserved physical quantity. ... Einstein elaborated in a 1946 essay that "the principle of the conservation of mass[...] proved inadequate in the face of the special theory of relativity.

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In physics, mass-energy equivalence is the relationship between mass and energy in a system's rest frame, where the two quantities differ only by a multiplicative constant and the units of measurement.[1] [2] The principle is described by the physicist Albert Einstein's famous formula: .[3] In a reference frame where the system is moving, its relativistic energy and relativistic mass (instead of rest mass) obey the same formula.

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In physics, the law of conservation of energy states that the total energy of an isolated system remains constant—it is said to be conserved over time. Energy can neither be created nor destroyed; rather, it transforms from one form to another.

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The law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be conserved over time. In the case of a closed system the principle says that the total amount of energy within the system can only be changed through energy entering or leaving the system. Energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another. For instance, chemical energy is converted to kinetic energy when a stick of dynamite explodes. If one adds up all forms of energy that were released in the explosion, such as the kinetic energy and potential energy of the pieces, as well as heat and sound, one will get the exact decrease of chemical energy in the combustion of the dynamite.

Classically, conservation of energy was distinct from conservation of mass. However, special relativity shows that mass is related to energy and vice versa by , the equation representing mass-energy equivalence, and science now takes the view that mass-energy as a whole is conserved. Theoretically, this implies that any object with mass can itself be converted to pure energy, and vice versa. However, this is believed to be possible only under the most extreme of physical conditions, such as likely existed in the universe very shortly after the Big Bang or when black holes emit Hawking radiation.

Given the stationary-action principle, conservation of energy can be rigorously proven by Noether's theorem as a consequence of continuous time translation symmetry; that is, from the fact that the laws of physics do not change over time.

A consequence of the law of conservation of energy is that a perpetual motion machine of the first kind cannot exist; that is to say, no system without an external energy supply can deliver an unlimited amount of energy to its surroundings. Depending on the definition of energy, conservation of energy can arguably be violated by general relativity on the cosmological scale.

Ancient philosophers as far back as Thales of Miletus c. 550 BCE had inklings of the conservation of some underlying substance of which everything is made. However, there is no particular reason to identify their theories with what we know today as "mass-energy" (for example, Thales thought it was water). Empedocles (490-430 BCE) wrote that in his universal system, composed of four roots (earth, air, water, fire), "nothing comes to be or perishes"; instead, these elements suffer continual rearrangement. Epicurus ( c. 350 BCE) on the other hand believed everything in the universe to be composed of indivisible units of matter-the ancient precursor to 'atoms'-and he too had some idea of the necessity of conservation, stating that "the sum total of things was always such as it is now, and such it will ever remain."

In 1605, the Flemish scientist Simon Stevin was able to solve a number of problems in statics based on the principle that perpetual motion was impossible.

In 1639, Galileo published his analysis of several situations-including the celebrated "interrupted pendulum"-which can be described (in modern language) as conservatively converting potential energy to kinetic energy and back again. Essentially, he pointed out that the height a moving body rises is equal to the height from which it falls, and used this observation to infer the idea of inertia. The remarkable aspect of this observation is that the height to which a moving body ascends on a frictionless surface does not depend on the shape of the surface.

In 1669, Christiaan Huygens published his laws of collision. Among the quantities he listed as being invariant before and after the collision of bodies were both the sum of their linear momenta as well as the sum of their kinetic energies. However, the difference between elastic and inelastic collision was not understood at the time. This led to the dispute among later researchers as to which of these conserved quantities was the more fundamental. In his Horologium Oscillatorium, he gave a much clearer statement regarding the height of ascent of a moving body, and connected this idea with the impossibility of perpetual motion. Huygens's study of the dynamics of pendulum motion was based on a single principle: that the center of gravity of a heavy object cannot lift itself.

Between 1676 and 1689, Gottfried Leibniz first attempted a mathematical formulation of the kind of energy that is associated with motion (kinetic energy). Using Huygens's work on collision, Leibniz noticed that in many mechanical systems (of several masses , each with velocity ),

was conserved so long as the masses did not interact. He called this quantity the or living force of the system. The principle represents an accurate statement of the approximate conservation of kinetic energy in situations where there is no friction. Many physicists at that time, including Isaac Newton, held that the conservation of momentum, which holds even in systems with friction, as defined by the momentum:

was the conserved vis viva. It was later shown that both quantities are conserved simultaneously given the proper conditions, such as in an elastic collision.

In 1687, Isaac Newton published his , which set out his laws of motion. It was organized around the concept of force and momentum. However, the researchers were quick to recognize that the principles set out in the book, while fine for point masses, were not sufficient to tackle the motions of rigid and fluid bodies. Some other principles were also required.

By the 1690s, Leibniz was arguing that conservation of vis viva and conservation of momentum undermined the then-popular philosophical doctrine of interactionist dualism. (During the 19th century, when conservation of energy was better understood, Leibniz's basic argument would gain widespread acceptance. Some modern scholars continue to champion specifically conservation-based attacks on dualism, while others subsume the argument into a more general argument about causal closure.)

The law of conservation of vis viva was championed by the father and son duo, Johann and Daniel Bernoulli. The former enunciated the principle of virtual work as used in statics in its full generality in 1715, while the latter based his Hydrodynamica, published in 1738, on this single vis viva conservation principle. Daniel's study of loss of vis viva of flowing water led him to formulate the Bernoulli's principle, which asserts the loss to be proportional to the change in hydrodynamic pressure. Daniel also formulated the notion of work and efficiency for hydraulic machines; and he gave a kinetic theory of gases, and linked the kinetic energy of gas molecules with the temperature of the gas.

This focus on the vis viva by the continental physicists eventually led to the discovery of stationarity principles governing mechanics, such as the D'Alembert's principle, Lagrangian, and Hamiltonian formulations of mechanics.

Émilie du Châtelet (1706-1749) proposed and tested the hypothesis of the conservation of total energy, as distinct from momentum. Inspired by the theories of Gottfried Leibniz, she repeated and publicized an experiment originally devised by Willem 's Gravesande in 1722 in which balls were dropped from different heights into a sheet of soft clay. Each ball's kinetic energy-as indicated by the quantity of material displaced-was shown to be proportional to the square of the velocity. The deformation of the clay was found to be directly proportional to the height from which the balls were dropped, equal to the initial potential energy. Some earlier workers, including Newton and Voltaire, had believed that "energy" was not distinct from momentum and therefore proportional to velocity. According to this understanding, the deformation of the clay should have been proportional to the square root of the height from which the balls were dropped. In classical physics, the correct formula is , where is the kinetic energy of an object, its mass and its speed. On this basis, du Châtelet proposed that energy must always have the same dimensions in any form, which is necessary to be able to consider it in different forms (kinetic, potential, heat, ...).[7][8]

Engineers such as John Smeaton, Peter Ewart, Carl Holtzmann, Gustave-Adolphe Hirn, and Marc Seguin recognized that conservation of momentum alone was not adequate for practical calculation and made use of Leibniz's principle. The principle was also championed by some chemists such as William Hyde Wollaston. Academics such as John Playfair were quick to point out that kinetic energy is clearly not conserved. This is obvious to a modern analysis based on the second law of thermodynamics, but in the 18th and 19th centuries, the fate of the lost energy was still unknown.

Gradually it came to be suspected that the heat inevitably generated by motion under friction was another form of vis viva. In 1783, Antoine Lavoisier and Pierre-Simon Laplace reviewed the two competing theories of vis viva and caloric theory. Count Rumford's 1798 observations of heat generation during the boring of cannons added more weight to the view that mechanical motion could be converted into heat and (that it was important) that the conversion was quantitative and could be predicted (allowing for a universal conversion constant between kinetic energy and heat). Vis viva then started to be known as energy, after the term was first used in that sense by Thomas Young in 1807.

The recalibration of vis viva to

which can be understood as converting kinetic energy to work, was largely the result of Gaspard-Gustave Coriolis and Jean-Victor Poncelet over the period 1819-1839. The former called the quantity quantité de travail (quantity of work) and the latter, travail mécanique (mechanical work), and both championed its use in engineering calculations.

In the paper Über die Natur der Wärme (German "On the Nature of Heat/Warmth"), published in the Zeitschrift für Physik in 1837, Karl Friedrich Mohr gave one of the earliest general statements of the doctrine of the conservation of energy: "besides the 54 known chemical elements there is in the physical world one agent only, and this is called Kraft [energy or work]. It may appear, according to circumstances, as motion, chemical affinity, cohesion, electricity, light and magnetism; and from any one of these forms it can be transformed into any of the others."

A key stage in the development of the modern conservation principle was the demonstration of the mechanical equivalent of heat. The caloric theory maintained that heat could neither be created nor destroyed, whereas conservation of energy entails the contrary principle that heat and mechanical work are interchangeable.

In the middle of the eighteenth century, Mikhail Lomonosov, a Russian scientist, postulated his corpusculo-kinetic theory of heat, which rejected the idea of a caloric. Through the results of empirical studies, Lomonosov came to the conclusion that heat was not transferred through the particles of the caloric fluid.

In 1798, Count Rumford ( Benjamin Thompson) performed measurements of the frictional heat generated in boring cannons and developed the idea that heat is a form of kinetic energy; his measurements refuted caloric theory, but were imprecise enough to leave room for doubt.

The mechanical equivalence principle was first stated in its modern form by the German surgeon Julius Robert von Mayer in 1842. Mayer reached his conclusion on a voyage to the Dutch East Indies, where he found that his patients' blood was a deeper red because they were consuming less oxygen, and therefore less energy, to maintain their body temperature in the hotter climate. He discovered that heat and mechanical work were both forms of energy, and in 1845, after improving his knowledge of physics, he published a monograph that stated a quantitative relationship between them.

Meanwhile, in 1843, James Prescott Joule independently discovered the mechanical equivalent in a series of experiments. In the most famous, now called the "Joule apparatus", a descending weight attached to a string caused a paddle immersed in water to rotate. He showed that the gravitational potential energy lost by the weight in descending was equal to the internal energy gained by the water through friction with the paddle.

Over the period 1840-1843, similar work was carried out by engineer Ludwig A. Colding, although it was little known outside his native Denmark.

Both Joule's and Mayer's work suffered from resistance and neglect but it was Joule's that eventually drew the wider recognition.

In 1844, the Welsh scientist William Robert Grove postulated a relationship between mechanics, heat, light, electricity, and magnetism by treating them all as manifestations of a single "force" ( energy in modern terms). In 1846, Grove published his theories in his book The Correlation of Physical Forces. In 1847, drawing on the earlier work of Joule, Sadi Carnot, and Émile Clapeyron, Hermann von Helmholtz arrived at conclusions similar to Grove's and published his theories in his book Über die Erhaltung der Kraft ( On the Conservation of Force, 1847). The general modern acceptance of the principle stems from this publication.

In 1850, the Scottish mathematician William Rankine first used the phrase the law of the conservation of energy for the principle.

In 1877, Peter Guthrie Tait claimed that the principle originated with Sir Isaac Newton, based on a creative reading of propositions 40 and 41 of the Philosophiae Naturalis Principia Mathematica. This is now regarded as an example of Whig history.

Mass-energy equivalence

Matter is composed of atoms and what makes up atoms. Matter has . In the limited range of recognized experience of the nineteenth century, it was found that such rest mass is conserved. Einstein's 1905 theory of special relativity showed that rest mass corresponds to an equivalent amount of rest energy. This means that rest mass can be converted to or from equivalent amounts of (non-material) forms of energy, for example, kinetic energy, potential energy, and electromagnetic radiant energy. When this happens, as recognized in twentieth-century experience, rest mass is not conserved, unlike the total mass or total energy. All forms of energy contribute to the total mass and total energy.

For example, an electron and a positron each have rest mass. They can perish together, converting their combined rest energy into photons which have electromagnetic radiant energy but no rest mass. If this occurs within an isolated system that does not release the photons or their energy into the external surroundings, then neither the total mass nor the total energy of the system will change. The produced electromagnetic radiant energy contributes just as much to the inertia (and to any weight) of the system as did the rest mass of the electron and positron before their demise. Likewise, non-material forms of energy can perish into matter, which has rest mass.

Thus, conservation of energy ( total, including material or rest energy) and conservation of mass ( total, not just rest) are one (equivalent) law. In the 18th century, these had appeared as two seemingly-distinct laws.

The discovery in 1911 that electrons emitted in beta decay have a continuous rather than a discrete spectrum appeared to contradict conservation of energy, under the then-current assumption that beta decay is the simple emission of an electron from a nucleus. This problem was eventually resolved in 1933 by Enrico Fermi who proposed the correct description of beta-decay as the emission of both an electron and an antineutrino, which carries away the apparently missing energy.

For a closed thermodynamic system, the first law of thermodynamics may be stated as:

, or equivalently,

where is the quantity of energy added to the system by a heating process, is the quantity of energy lost by the system due to work done by the system on its surroundings, and is the change in the internal energy of the system.

The δ's before the heat and work terms are used to indicate that they describe an increment of energy which is to be interpreted somewhat differently than the increment of internal energy (see Inexact differential). Work and heat refer to kinds of process which add or subtract energy to or from a system, while the internal energy is a property of a particular state of the system when it is in unchanging thermodynamic equilibrium. Thus the term "heat energy" for means "that amount of energy added as a result of heating" rather than referring to a particular form of energy. Likewise, the term "work energy" for means "that amount of energy lost as a result of work". Thus one can state the amount of internal energy possessed by a thermodynamic system that one knows is presently in a given state, but one cannot tell, just from knowledge of the given present state, how much energy has in the past flowed into or out of the system as a result of its being heated or cooled, nor as a result of work being performed on or by the system.

Entropy is a function of the state of a system which tells of limitations of the possibility of conversion of heat into work.

For a simple compressible system, the work performed by the system may be written:

where is the pressure and is a small change in the volume of the system, each of which are system variables. In the fictive case in which the process is idealized and infinitely slow, so as to be called quasi-static, and regarded as reversible, the heat being transferred from a source with temperature infinitesimally above the system temperature, the heat energy may be written

where is the temperature and is a small change in the entropy of the system. Temperature and entropy are variables of the state of a system.

If an open system (in which mass may be exchanged with the environment) has several walls such that the mass transfer is through rigid walls separate from the heat and work transfers, then the first law may be written as

where is the added mass of species and is the corresponding enthalpy per unit mass. Note that generally in this case, as matter carries its own entropy. Instead, , where is the entropy per unit mass of type , from which we recover the fundamental thermodynamic relation

because the chemical potential is the partial molar Gibbs free energy of species and the Gibbs free energy .

Noether's theorem

Emmy Noether (1882-1935) was an influential mathematician known for her groundbreaking contributions to abstract algebra and theoretical physics.

The conservation of energy is a common feature in many physical theories. From a mathematical point of view it is understood as a consequence of Noether's theorem, developed by Emmy Noether in 1915 and first published in 1918. In any physical theory that obeys the stationary-action principle, the theorem states that every continuous symmetry has an associated conserved quantity; if the theory's symmetry is time invariance, then the conserved quantity is called "energy". The energy conservation law is a consequence of the shift symmetry of time; energy conservation is implied by the empirical fact that the laws of physics do not change with time itself. Philosophically this can be stated as "nothing depends on time per se". In other words, if the physical system is invariant under the continuous symmetry of time translation, then its energy (which is the canonical conjugate quantity to time) is conserved. Conversely, systems that are not invariant under shifts in time (e.g. systems with time-dependent potential energy) do not exhibit conservation of energy - unless we consider them to exchange energy with another, an external system so that the theory of the enlarged system becomes time-invariant again. Conservation of energy for finite systems is valid in physical theories such as special relativity and quantum theory (including QED) in the flat space-time.

With the discovery of special relativity by Henri Poincaré and Albert Einstein, the energy was proposed to be a component of an energy-momentum 4-vector. Each of the four components (one of energy and three of momentum) of this vector is separately conserved across time, in any closed system, as seen from any given inertial reference frame. Also conserved is the vector length ( Minkowski norm), which is the rest mass for single particles, and the invariant mass for systems of particles (where momenta and energy are separately summed before the length is calculated).

The relativistic energy of a single massive particle contains a term related to its rest mass in addition to its kinetic energy of motion. In the limit of zero kinetic energy (or equivalently in the rest frame) of a massive particle, or else in the center of momentum frame for objects or systems which retain kinetic energy, the total energy of a particle or object (including internal kinetic energy in systems) is proportional to the rest mass or invariant mass, as described by the famous equation .

Thus, the rule of conservation of energy over time in special relativity continues to hold, so long as the reference frame of the observer is unchanged. This applies to the total energy of systems, although different observers disagree as to the energy value. Also conserved, and invariant to all observers, is the invariant mass, which is the minimal system mass and energy that can be seen by any observer, and which is defined by the energy-momentum relation.

General relativity introduces new phenomena. In an expanding universe, photons spontaneously redshift and tethers spontaneously gain tension; if vacuum energy is positive, the total vacuum energy of the universe appears to spontaneously increase as the volume of space increases. Some scholars claim that energy is no longer meaningfully conserved in any identifiable form.

John Baez's view is that energy-momentum conservation is not well-defined except in certain special cases. Energy-momentum is typically expressed with the aid of a stress-energy-momentum pseudotensor. However, since pseudotensors are not tensors, they do not transform cleanly between reference frames. If the metric under consideration is static (that is, does not change with time) or asymptotically flat (that is, at an infinite distance away spacetime looks empty), then energy conservation holds without major pitfalls. In practice, some metrics, notably the Friedmann-Lemaître-Robertson-Walker metric that appears to govern the universe, do not satisfy these constraints and energy conservation is not well defined. Besides being dependent on the coordinate system, pseudotensor energy is dependent on the type of pseudotensor in use; for example, the energy exterior to a Kerr-Newman black hole is twice as large when calculated from Møller's pseudotensor as it is when calculated using the Einstein pseudotensor.

For asymptotically flat universes, Einstein and others salvage conservation of energy by introducing a specific global gravitational potential energy that cancels out mass-energy changes triggered by spacetime expansion or contraction. This global energy has no well-defined density and cannot technically be applied to a non-asymptotically flat universe; however, for practical purposes this can be finessed, and so by this view, energy is conserved in our universe. Alan Guth even famously stated that the universe might be "the ultimate free lunch", and theorized that, when accounting for gravitational potential energy, the net energy of the Universe is zero.

In quantum mechanics, the energy of a quantum system is described by a self-adjoint (or Hermitian) operator called the Hamiltonian, which acts on the Hilbert space (or a space of wave functions) of the system. If the Hamiltonian is a time-independent operator, emergence probability of the measurement result does not change in time over the evolution of the system. Thus the expectation value of energy is also time independent. The local energy conservation in quantum field theory is ensured by the quantum Noether's theorem for the energy-momentum tensor operator. Thus energy is conserved by the normal unitary evolution of a quantum system.

However, when the non-unitary Born rule is applied, the system's energy is measured with an energy that can be below or above the expectation value, if the system was not in an energy eigenstate. (For macroscopic systems, this effect is usually too small to measure.) The disposition of this energy gap is not well-understood; some physicists believe that the energy is transferred to or from the macroscopic environment in the course of the measurement process, while others believe that the observable energy is only conserved "on average". No experiment has been confirmed as definitive evidence of violations of the conservation of energy principle in quantum mechanics, but that doesn't rule out that some newer experiments, as proposed, may find evidence of violations of the conservation of energy principle in quantum mechanics.

In the context of perpetual motion machines such as the Orbo, Professor Eric Ash has argued at the BBC: "Denying [conservation of energy] would undermine not just little bits of science - the whole edifice would be no more. All of the technology on which we built the modern world would lie in ruins." It is because of conservation of energy that "we know - without having to examine details of a particular device - that Orbo cannot work."

Energy conservation has been a foundational physical principle for about two hundred years. From the point of view of modern general relativity, the lab environment can be well approximated by Minkowski spacetime, where energy is exactly conserved. The entire Earth can be well approximated by the Schwarzschild metric, where again energy is exactly conserved. Given all the experimental evidence, any new theory (such as quantum gravity), in order to be successful, will have to explain why energy has appeared to always be exactly conserved in terrestrial experiments. In some speculative theories, corrections to quantum mechanics are too small to be detected at anywhere near the current TeV level accessible through particle accelerators. Doubly special relativity models may argue for a breakdown in energy-momentum conservation for sufficiently energetic particles; such models are constrained by observations that cosmic rays appear to travel for billions of years without displaying anomalous non-conservation behavior. Some interpretations of quantum mechanics claim that observed energy tends to increase when the Born rule is applied due to localization of the wave function. If true, objects could be expected to spontaneously heat up; thus, such models are constrained by observations of large, cool astronomical objects as well as the observation of (often supercooled) laboratory experiments.

Milton A. Rothman wrote that the law of conservation of energy has been verified by nuclear physics experiments to an accuracy of one part in a thousand million million (10 ¹⁵). He then defines its precision as "perfect for all practical purposes".

1. Planck, M. (1923/1927). ^ Treatise on Thermodynamics, third English edition translated by A. Ogg from the seventh German edition, Longmans, Green & Co., London, page 40.

2. ^ Laertius, Diogenes. Lives of Eminent Philosophers: Epicurus.. This passage comes from a letter quoted in full by Diogenes, and purportedly written by Epicurus himself in which he lays out the tenets of his philosophy.

3. ^ Pitts, J. Brian (September 2021). "Conservation of Energy: Missing Features in Its Nature and Justification and Why They Matter". Foundations of Science. 26 (3): 559-584. doi:10.1007/s10699-020-09657-1. PMC . PMID 34759713.

4. Hagengruber, Ruth, editor (2011) ^ Émilie du Chatelet between Leibniz and Newton. Springer. ISBN 978-94-007-2074-9.

5. Lavoisier, A.L. & Laplace, P.S. (1780) "Memoir on Heat", ^ Académie Royale des Sciences pp. 4-355

6. ^ Guerlac, Henry (1976). "Chemistry as a Branch of Physics: Laplace's Collaboration with Lavoisier". Historical Studies in the Physical Sciences. University of California Press. 7: 193-276. doi:10.2307/27757357. JSTOR 27757357.

7. von Mayer, J.R. (1842) "Remarks on the forces of inorganic nature" in ^ Annalen der Chemie und Pharmacie, 43, 233

8. Mayer, J.R. (1845). ^ Die organische Bewegung in ihrem Zusammenhange mit dem Stoffwechsel. Ein Beitrag zur Naturkunde, Dechsler, Heilbronn.

9. William John Macquorn Rankine (1853) "On the General Law of the Transformation of Energy," ^ Proceedings of the Philosophical Society of Glasgow, vol. 3, no. 5, pages 276-280; reprinted in: (1) Philosophical Magazine, series 4, vol. 5, no. 30, pages 106-117 (February 1853); and (2) W. J. Millar, ed., Miscellaneous Scientific Papers: by W. J. Macquorn Rankine, ... (London, England: Charles Griffin and Co., 1881), part II, pages 203-208: "The law of the Conservation of Energy is already known-viz. that the sum of all the energies of the universe, actual and potential, is unchangeable."

10. ^ Knuiman, Jan T.; Barneveld, Peter A.; Besseling, Nicolaas A. M. (2012). "On the Relation between the Fundamental Equation of Thermodynamics and the Energy Balance Equation in the Context of Closed and Open Systems". Journal of Chemical Education. 89 (8): 968-972. Bibcode:2012JChEd..89..968K. doi:10.1021/ed200405k.

11. ^ Hanc, J., Tuleja, S., & Hancova, M. (2004). Symmetries and conservation laws: Consequences of Noether's theorem. American Journal of Physics, 72(4), 428-435.

12. ^ Harrison, E. R. (1995). Mining energy in an expanding universe. The Astrophysical Journal, 446, 63.

13. ^ Michael Weiss; John Baez. "Is Energy Conserved in General Relativity?". Archived from the original on 5 June 2007.

14. ^ Duerr, Patrick M. (February 2019). "Fantastic Beasts and where (not) to find them: Local gravitational energy and energy conservation in general relativity". Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics. 65: 1-14. Bibcode:2019SHPMP..65....1D. doi:10.1016/j.shpsb.2018.07.002. S2CID 126366668.

15. ^ Maudlin, Tim; Okon, Elias; Sudarsky, Daniel (February 2020). "On the status of conservation laws in physics: Implications for semiclassical gravity". Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics. 69: 67-81. arXiv:. Bibcode:2020SHPMP..69...67M. doi:10.1016/j.shpsb.2019.10.004. S2CID 204575731.

16. ^ Carlesso, Matteo; Donadi, Sandro; Ferialdi, Luca; Paternostro, Mauro; Ulbricht, Hendrik; Bassi, Angelo (March 2022). "Present status and future challenges of non-interferometric tests of collapse models". Nature Physics. 18 (3): 243-250. arXiv:. Bibcode:2022NatPh..18..243C. doi:10.1038/s41567-021-01489-5. S2CID 246949254.

17. ^ Rothman, Milton (1989). "Myths About Science... And Belief in the Paranormal". The Skeptical Inquirer. 14 (1): 28.

Goldstein, Martin, and Inge F., (1993). The Refrigerator and the Universe. Harvard Univ. Press. A gentle introduction.

Nolan, Peter J. (1996). Fundamentals of College Physics, 2nd ed. William C. Brown Publishers.

Oxtoby & Nachtrieb (1996). Principles of Modern Chemistry, 3rd ed. Saunders College Publishing.

Papineau, D. (2002). Thinking about Consciousness. Oxford: Oxford University Press.

Serway, Raymond A.; Jewett, John W. (2004). Physics for Scientists and Engineers (6th ed.). Brooks/Cole. ISBN 978-0-534-40842-8.

Stenger, Victor J. (2000). Timeless Reality. Prometheus Books. Especially chpt. 12. Nontechnical.

Lanczos, Cornelius (1970). The Variational Principles of Mechanics. Toronto: University of Toronto Press. ISBN 978-0-8020-1743-7.

Brown, T.M. (1965). "Resource letter EEC-1 on the evolution of energy concepts from Galileo to Helmholtz". American Journal of Physics. 33 (10): 759-765. Bibcode:1965AmJPh..33..759B. doi:10.1119/1.1970980.

Guillen, M. (1999). Five Equations That Changed the World. New York: Abacus. ISBN 978-0-349-11064-6.

Kuhn, T.S. (1957) "Energy conservation as an example of simultaneous discovery", in M. Clagett (ed.) Critical Problems in the History of Science pp.321-56

Sarton, G.; Joule, J. P.; Carnot, Sadi (1929). "The discovery of the law of conservation of energy". Isis. 13: 18-49. doi:10.1086/346430. S2CID 145585492.

Mach, E. (1872). History and Root of the Principles of the Conservation of Energy. Open Court Pub. Co., Illinois.

Poincaré, H. (1905). Science and Hypothesis. Walter Scott Publishing Co. Ltd; Dover reprint, 1952. ISBN 978-0-486-60221-9., Chapter 8, "Energy and Thermo-dynamics"

# data[].attributes.attachment_link.description
The law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be conserved over time. In the case of a closed system the principle says that the total amount of energy within the system can only be changed through energy entering or leaving the system.

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A scientific law is a statement based on repeated experimental observations that describes some aspects of the universe. A scientific law always applies under the same conditions, and implies that there is a causal relationship involving its elements.

# data[].attributes.attachment_link.description
The laws of science, also called scientific laws or scientific principles, are statements that describe or predict a range of natural phenomena. Each scientific law is a statement based on repeated experimental observations that describes some aspect of the Universe.

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The law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as system mass cannot change quantity if it is not added or removed. Hence, the quantity of mass is "conserved" over time.

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The law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as system's mass cannot change, so quantity can neither be added nor be removed. Hence, the quantity of mass is conserved over time.

The law implies that mass can neither be created nor destroyed, although it may be rearranged in space, or the entities associated with it may be changed in form. For example, in chemical reactions, the mass of the chemical components before the reaction is equal to the mass of the components after the reaction. Thus, during any chemical reaction and low-energy thermodynamic processes in an isolated system, the total mass of the reactants, or starting materials, must be equal to the mass of the products.

The concept of mass conservation is widely used in many fields such as chemistry, mechanics, and fluid dynamics. Historically, mass conservation was demonstrated in chemical reactions independently by Mikhail Lomonosov and later rediscovered by Antoine Lavoisier in the late 18th century. The formulation of this law was of crucial importance in the progress from alchemy to the modern natural science of chemistry.

The conservation of mass only holds approximately and is considered part of a series of assumptions coming from classical mechanics. The law has to be modified to comply with the laws of quantum mechanics and special relativity under the principle of mass-energy equivalence, which states that energy and mass form one conserved quantity. For very energetic systems the conservation of mass-only is shown not to hold, as is the case in nuclear reactions and particle-antiparticle annihilation in particle physics.

Mass is also not generally conserved in open systems. Such is the case when various forms of energy and matter are allowed into, or out of, the system. However, unless radioactivity or nuclear reactions are involved, the amount of energy escaping (or entering) such systems as heat, mechanical work, or electromagnetic radiation is usually too small to be measured as a decrease (or increase) in the mass of the system.

For systems where large gravitational fields are involved, general relativity has to be taken into account, where mass-energy conservation becomes a more complex concept, subject to different definitions, and neither mass nor energy is as strictly and simply conserved as is the case in special relativity.

The law of conservation of mass can only be formulated in classical mechanics when the energy scales associated to an isolated system are much smaller than , where is the mass of a typical object in the system, measured in the frame of reference where the object is at rest, and is the speed of light.

The law can be formulated mathematically in the fields of fluid mechanics and continuum mechanics, where the conservation of mass is usually expressed using the continuity equation, given in differential form as

where is the density (mass per unit volume), is the time, is the divergence, and is the flow velocity field. The interpretation of the continuity equation for mass is the following: For a given closed surface in the system, the change in time of the mass enclosed by the surface is equal to the mass that traverses the surface, positive if matter goes in and negative if matter goes out. For the whole isolated system, this condition implies that the total mass , sum of the masses of all components in the system, does not change in time, i.e.

,

where is the differential that defines the integral over the whole volume of the system.

The continuity equation for the mass is part of Euler equations of fluid dynamics. Many other convection-diffusion equations describe the conservation and flow of mass and matter in a given system.

In chemistry, the calculation of the amount of reactant and products in a chemical reaction, or stoichiometry, is founded on the principle of conservation of mass. The principle implies that during a chemical reaction the total mass of the reactants is equal to the total mass of the products. For example, in the following reaction

where one molecule of methane () and two oxygen molecules are converted into one molecule of carbon dioxide () and two of water (). The number of molecules as result from the reaction can be derived from the principle of conservation of mass, as initially four hydrogen atoms, 4 oxygen atoms and one carbon atom are present (as well as in the final state), then the number water molecules produced must be exactly two per molecule of carbon dioxide produced.

Many engineering problems are solved by following the mass distribution in time of a given system, this practice is known as mass balance.

An important idea in ancient Greek philosophy was that " Nothing comes from nothing", so that what exists now has always existed: no new matter can come into existence where there was none before. An explicit statement of this, along with the further principle that nothing can pass away into nothing, is found in Empedocles (approx. 4th century BC): "For it is impossible for anything to come to be from what is not, and it cannot be brought about or heard of that what is should be utterly destroyed."

A further principle of conservation was stated by Epicurus around 3rd century BC, who, describing the nature of the Universe, wrote that "the totality of things was always such as it is now, and always will be".

Jain philosophy, a non-creationist philosophy based on the teachings of Mahavira (6th century BC), states that the universe and its constituents such as matter cannot be destroyed or created. The Jain text Tattvarthasutra (2nd century CE) states that a substance is permanent, but its modes are characterised by creation and destruction. A principle of the conservation of matter was also stated by Nasīr al-Dīn al-Tūsī (around 13th century CE). He wrote that "A body of matter cannot disappear completely. It only changes its form, condition, composition, color and other properties and turns into a different complex or elementary matter".

By the 18th century the principle of conservation of mass during chemical reactions was widely used and was an important assumption during experiments, even before a definition was formally established, as can be seen in the works of Joseph Black, Henry Cavendish, and Jean Rey. The first to outline the principle was given by Mikhail Lomonosov in 1756. He demonstrated it by experiments and had discussed the principle before in 1774 in correspondence with Leonhard Euler, though his claim on the subject is sometimes challenged. A more refined series of experiments were later carried out by Antoine Lavoisier who expressed his conclusion in 1773 and popularized the principle of conservation of mass. The demonstrations of the principle led alternatives theories obsolete, like the phlogiston theory that claimed that mass could be gained or lost in combustion and heat processes.

The conservation of mass was obscure for millennia because of the buoyancy effect of the Earth's atmosphere on the weight of gases. For example, a piece of wood weighs less after burning; this seemed to suggest that some of its mass disappears, or is transformed or lost. This was not disproved until careful experiments were performed in which chemical reactions such as rusting were allowed to take place in sealed glass ampoules; it was found that the chemical reaction did not change the weight of the sealed container and its contents. Weighing of gases using scales was not possible until the invention of the vacuum pump in 17th century.

Once understood, the conservation of mass was of great importance in progressing from alchemy to modern chemistry. Once early chemists realized that chemical substances never disappeared but were only transformed into other substances with the same weight, these scientists could for the first time embark on quantitative studies of the transformations of substances. The idea of mass conservation plus a surmise that certain "elemental substances" also could not be transformed into others by chemical reactions, in turn led to an understanding of chemical elements, as well as the idea that all chemical processes and transformations (such as burning and metabolic reactions) are reactions between invariant amounts or weights of these chemical elements.

Following the pioneering work of Lavoisier, the exhaustive experiments of Jean Stas supported the consistency of this law in chemical reactions, even though they were carried out with other intentions. His research indicated that in certain reactions the loss or gain could not have been more than from 2 to 4 parts in 100,000. The difference in the accuracy aimed at and attained by Lavoisier on the one hand, and by Morley and Stas on the other, is enormous.

The law of conservation of mass was challenged with the advent of special relativity. In one of the Annus Mirabilis papers of Albert Einstein in 1905, he suggested an equivalence between mass and energy. This theory implied several assertions, like the idea that internal energy of a system could contribute to the mass of the whole system, or that mass could be converted into electromagnetic radiation. However, as Max Planck pointed out, a change in mass as a result of extraction or addition of chemical energy, as predicted by Einstein's theory, is so small that it could not be measured with the available instruments and could not be presented as a test to the special relativity. Einstein speculated that the energies associated with newly discovered radioactivity were significant enough, compared with the mass of systems producing them, to enable their mass-change to be measured, once the energy of the reaction had been removed from the system. This later indeed proved to be possible, although it was eventually to be the first artificial nuclear transmutation reaction in 1932, demonstrated by Cockcroft and Walton, that proved the first successful test of Einstein's theory regarding mass-loss with energy-loss.

The law conservation of mass and the analogous law of conservation of energy were finally overruled by a more general principle known as the mass-energy equivalence. Special relativity also redefines the concept of mass and energy, which can be used interchangeably and are relative to the frame of reference. Several definitions had to be defined for consistency like of a particle (mass in the rest frame of the particle) and relativistic mass (in another frame). The latter term is usually less frequently used. For more discussion, see Mass in special relativity.

In special relativity, the conservation of mass does not apply if the system is open and energy escapes. However, it does continue to apply to totally closed (isolated) systems. If energy cannot escape a system, its mass cannot decrease. In relativity theory, so long as any type of energy is retained within a system, this energy exhibits mass.

Also, mass must be differentiated from (see below), since matter may not be perfectly conserved in isolated systems, even though mass is always conserved in such systems. However, matter is so nearly conserved in chemistry that violations of matter conservation were not measured until the nuclear age, and the assumption of matter conservation remains an important practical concept in most systems in chemistry and other studies that do not involve the high energies typical of radioactivity and nuclear reactions.

The mass associated with chemical amounts of energy is too small to measure

The change in mass of certain kinds of open systems where atoms or massive particles are not allowed to escape, but other types of energy (such as light or heat) are allowed to enter or escape, went unnoticed during the 19th century, because the change in mass associated with addition or loss of small quantities of thermal or radiant energy in chemical reactions is very small. (In theory, mass would not change at all for experiments conducted in isolated systems where heat and work were not allowed in or out.)

Mass conservation remains correct if energy is not lost

The conservation of relativistic mass implies the viewpoint of a single observer (or the view from a single inertial frame) since changing inertial frames may result in a change of the total energy (relativistic energy) for systems, and this quantity determines the relativistic mass.

The principle that the mass of a system of particles must be equal to the sum of their rest masses, even though true in classical physics, may be false in special relativity. The reason that rest masses cannot be simply added is that this does not take into account other forms of energy, such as kinetic and potential energy, and massless particles such as photons, all of which may (or may not) affect the total mass of systems.

For moving massive particles in a system, examining the rest masses of the various particles also amounts to introducing many different inertial observation frames (which is prohibited if total system energy and momentum are to be conserved), and also when in the rest frame of one particle, this procedure ignores the momenta of other particles, which affect the system mass if the other particles are in motion in this frame.

For the special type of mass called invariant mass, changing the inertial frame of observation for a whole closed system has no effect on the measure of invariant mass of the system, which remains both conserved and invariant (unchanging), even for different observers who view the entire system. Invariant mass is a system combination of energy and momentum, which is invariant for any observer, because in any inertial frame, the energies and momenta of the various particles always add to the same quantity (the momentum may be negative, so the addition amounts to a subtraction). The invariant mass is the relativistic mass of the system when viewed in the center of momentum frame. It is the minimum mass which a system may exhibit, as viewed from all possible inertial frames.

The conservation of both relativistic and invariant mass applies even to systems of particles created by pair production, where energy for new particles may come from kinetic energy of other particles, or from one or more photons as part of a system that includes other particles besides a photon. Again, neither the relativistic nor the invariant mass of totally closed (that is, isolated) systems changes when new particles are created. However, different inertial observers will disagree on the value of this conserved mass, if it is the relativistic mass (i.e., relativistic mass is conserved but not invariant). However, all observers agree on the value of the conserved mass if the mass being measured is the invariant mass (i.e., invariant mass is both conserved and invariant).

The mass-energy equivalence formula gives a different prediction in non- isolated systems, since if energy is allowed to escape a system, both relativistic mass and invariant mass will escape also. In this case, the mass-energy equivalence formula predicts that the change in mass of a system is associated with the change in its energy due to energy being added or subtracted: This form involving changes was the form in which this famous equation was originally presented by Einstein. In this sense, mass changes in any system are explained simply if the mass of the energy added or removed from the system, are taken into account.

The formula implies that bound systems have an invariant mass (rest mass for the system) less than the sum of their parts, if the binding energy has been allowed to escape the system after the system has been bound. This may happen by converting system potential energy into some other kind of active energy, such as kinetic energy or photons, which easily escape a bound system. The difference in system masses, called a mass defect, is a measure of the binding energy in bound systems - in other words, the energy needed to break the system apart. The greater the mass defect, the larger the binding energy. The binding energy (which itself has mass) must be released (as light or heat) when the parts combine to form the bound system, and this is the reason the mass of the bound system decreases when the energy leaves the system. The total invariant mass is actually conserved, when the mass of the binding energy that has escaped, is taken into account.

In general relativity, the total invariant mass of photons in an expanding volume of space will decrease, due to the red shift of such an expansions. The conservation of both mass and energy therefore depends on various corrections made to energy in the theory, due to the changing gravitational potential energy of such systems.

1. ^ Volkenstein, Mikhail V. (2009). Entropy and Information (illustrated ed.). Springer Science & Business Media. p. 20. ISBN 978-3-0346-0078-1. Extract of page 20

2. ^ Lewis, David (2012). Early Russian Organic Chemists and Their Legacy (illustrated ed.). Springer Science & Business Media. p. 29. ISBN 978-3-642-28219-5. Extract of page 29

3. Fr. 12; see pp.291-2 of ^ Kirk, G. S.; J. E. Raven; Malcolm Schofield (1983). The Presocratic Philosophers (2 ed.). Cambridge: Cambridge University Press. ISBN 978-0-521-27455-5.

4. ^ Long, A. A.; D. N. Sedley (1987). "Epicureanism: The principals of conservation". The Hellenistic Philosophers. Vol 1: Translations of the principal sources with philosophical commentary. Cambridge: Cambridge University Press. pp. 25-26. ISBN 978-0-521-27556-9.

5. Devendra (Muni.), T. G. Kalghatgi, T. S. Devadoss (1983) ^ A source-book in Jaina philosophy Udaipur:Sri Tarak Guru Jain Gran. p.57. Also see Tattvarthasutra verses 5.29 and 5.37

6. Farid Alakbarov (Summer 2001). ^ A 13th-Century Darwin? Tusi's Views on Evolution, Azerbaijan International 9 (2).

7. ^ Whitaker, Robert D. (1975-10-01). "An historical note on the conservation of mass". Journal of Chemical Education. 52 (10): 658. Bibcode:1975JChEd..52..658W. doi:10.1021/ed052p658. ISSN 0021-9584.

8. Robert D. Whitaker, "^ An Historical Note on the Conservation of Mass", Journal of Chemical Education, 52, 10, 658-659, Oct 75

9. ^ Pomper, Philip (October 1962). "Lomonosov and the Discovery of the Law of the Conservation of Matter in Chemical Transformations". Ambix. 10 (3): 119-127. doi:10.1179/amb.1962.10.3.119.

10. ^ Lomonosov, Mikhail Vasil'evich (1970). Mikhail Vasil'evich Lomonosov on the Corpuscular Theory. Henry M. Leicester (trans.). Cambridge, Mass.: Harvard University Press. Introduction, p. 25.

11. ^ Nouv. Recherches sur les lois des proportions chimiques (1865) 152, 171, 189

12. "Conservation of Mass in Chemical Changes"^ Journal - Chemical Society, London, Vol.64, Part 2 Chemical Society (Great Britain)

13. ^ Ida Freund, The study of Chemical Composition: an account of its method and historical development, with illustrative quotations (1904)

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The law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as system's mass cannot change, so quantity can neither be added nor be removed.

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How light energy is transformed into chemical energy

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How light energy is transformed into chemical energy

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Conversion of light energy to chemical energy. Light energy is converted to chemical energy when a photo chemically excited special chlorophyll molecule of the photosynthetic reaction center loses an electron, undergoing an oxidation reaction.

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The conversion of light energy to chemical energy is summarized in the diagram to the right. Light energy from the absorption of a photon excites an electron of P680 (photosystem II) or P700 (photosystem I) to a higher energy level. The reducing power of the electron is increased approximately 1 volt.

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The Calvin cycle refers to the light-independent reactions in photosynthesis that take place in three key steps. Although the Calvin Cycle is not directly dependent on light, it is indirectly dependent on light since the necessary energy carriers (ATP and NADPH) are products of light-dependent reactions.

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Photosynthesis takes place in two stages: light-dependent reactions and the Calvin cycle (light-independent reactions). Light-dependent reactions, which take place in the thylakoid membrane, use lightenergy to make ATP and NADPH.

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organelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis. It is the primary pigment in photosynthetic plants

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a set of chemical symbols showing the elements present in a compound and their relative proportions, and in some cases the structure of the compound.

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The simplest types of chemical formulas are called empirical formulas , which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the simple numbers of each type of atom in a molecule, with no information on structure.

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Inputs/ outputs (reactants vs products) 

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Inputs/ outputs (reactants vs products) 

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All chemical reactions involve both reactants and products. reactant are substances that start a chemical reaction, and products are substances that are produced in the reaction

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Reactants and products in chemical reactions and the relationship between reactants and products.

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Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities (energy transformation).

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Photosynthesis ( FOH-tə-SINTH-ə-sis ) is a biological process used by many cellular organisms to convert light energy into chemical energy, which is stored in organic compounds that can later be metabolized through cellular respiration to fuel the organism's activities.