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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 works with cell. respiration because they both have their own roles. Photosyn. makes glucose which is used in cell. resp. to make ATP then the glucose is turned into CO2 which is also used in cell. resp. While H2O absorbed is being broken down to form oxygen during photosynthesis, cell. resp. is combining H and O

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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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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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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.

# data[].attributes.attachment_link.description
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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Proteins, Lipids, Carbohydrates, Nucleic Acids

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Proteins, Lipids, Carbohydrates, Nucleic Acids

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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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Decomposers and scavengers break down dead plants and animals. They also break down the waste (poop) of other organisms. Decomposers are very important for any ecosystem. If they weren't in the ecosystem, the plants would not get essential nutrients, and dead matter and waste would pile up.

There are two kinds of decomposers, scavengers and decomposers.

Scavengers are animals that find dead animals or plants and eat them. While they eat them, they break them into small bits. In this simulation, flies, wasps and cockroaches are scavengers. Earthworms are also scavengers, but they only break down plants.

Once a scavenger is done, the decomposers take over, and finish the job. Many kinds of decomposers are microscopic, meaning that they can't be seen without a microscope. Others, like fungi, can be seen.

Different kinds of decomposers do different jobs in the ecosystem.

Others, like some kinds of bacteria, prefer breaking down meat or waste from carnivores.

Actinolites only break down dead plants, including hard to break down plants and the waste of herbivores.

Others, like certain kinds of fungi, prefer fruits and vegetables.

GO
TO:

Herbivores

Plants

Omnivores

Carnivores

Decomposers

Pollinators

Ecodome

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Decomposers and scavengers break down dead plants and animals. They also break down the waste (poop) of other organisms. Decomposers are very important for any ecosystem. If they weren't in the ecosystem, the plants would not get essential nutrients, and dead matter and waste would pile up.

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Since carnivores have to hunt down and kill other animals they require a large amount of calories. This means that they have to eat many other animals over the course of the year. The bigger the carnivore, the more it has to eat. You should make sure that you have many more herbivores and omnivores than carnivores.

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A herbivore is an animal that gets its energy from eating plants, and only plants. Omnivores can also eat parts of plants, but generally only the fruits and vegetables produced by fruit-bearing plants. Many herbivores have special digestive systems that let them digest all kinds of plants, including grasses.

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A heterotroph (; from Ancient Greek 'other', and 'nutrition') is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but not producers. Living organisms that are heterotrophic include all animals and fungi, some bacteria and protists, and many parasitic plants. The term heterotroph arose in microbiology in 1946 as part of a classification of microorganisms based on their type of nutrition. The term is now used in many fields, such as ecology in describing the food chain.

Heterotrophs may be subdivided according to their energy source. If the heterotroph uses chemical energy, it is a chemoheterotroph (e.g., humans and mushrooms). If it uses light for energy, then it is a photoheterotroph (e.g., green non-sulfur bacteria).

Heterotrophs represent one of the two mechanisms of nutrition ( trophic levels), the other being autotrophs ( auto = self, troph = nutrition). Autotrophs use energy from sunlight ( photoautotrophs) or oxidation of inorganic compounds ( lithoautotrophs) to convert inorganic carbon dioxide to organic carbon compounds and energy to sustain their life. Comparing the two in basic terms, heterotrophs (such as animals) eat either autotrophs (such as plants) or other heterotrophs, or both.

Detritivores are heterotrophs which obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). Saprotrophs (also called lysotrophs) are chemoheterotrophs that use extracellular digestion in processing decayed organic matter. The process is most often facilitated through the active transport of such materials through endocytosis within the internal mycelium and its constituent hyphae.

Heterotrophs can be organotrophs or lithotrophs. Organotrophs exploit reduced carbon compounds as electron sources, like carbohydrates, fats, and proteins from plants and animals. On the other hand, lithoheterotrophs use inorganic compounds, such as ammonium, nitrite, or sulfur, to obtain electrons. Another way of classifying different heterotrophs is by assigning them as chemotrophs or phototrophs. Phototrophs utilize light to obtain energy and carry out metabolic processes, whereas chemotrophs use the energy obtained by the oxidation of chemicals from their environment.

Photoorganoheterotrophs, such as Rhodospirillaceae and purple non-sulfur bacteria synthesize organic compounds using sunlight coupled with oxidation of organic substances. They use organic compounds to build structures. They do not fix carbon dioxide and apparently do not have the Calvin cycle. Chemolithoheterotrophs like Oceanithermus profundus obtain energy from the oxidation of inorganic compounds, including hydrogen sulfide, elemental sulfur, thiosulfate, and molecular hydrogen. Mixotrophs (or facultative chemolithotroph) can use either carbon dioxide or organic carbon as the carbon source, meaning that mixotrophs have the ability to use both heterotrophic and autotrophic methods. Although mixotrophs have the ability to grow under both heterotrophic and autotrophic conditions, C. vulgaris have higher biomass and lipid productivity when growing under heterotrophic compared to autotrophic conditions.

Heterotrophs, by consuming reduced carbon compounds, are able to use all the energy that they obtain from food for growth and reproduction, unlike autotrophs, which must use some of their energy for carbon fixation. Both heterotrophs and autotrophs alike are usually dependent on the metabolic activities of other organisms for nutrients other than carbon, including nitrogen, phosphorus, and sulfur, and can die from lack of food that supplies these nutrients. This applies not only to animals and fungi but also to bacteria.

The chemical origin of life hypothesis suggests that life originated in a prebiotic soup with heterotrophs. The summary of this theory is as follows: early Earth had a highly reducing atmosphere and energy sources such as electrical energy in the form of lightning, which resulted in reactions that formed simple organic compounds, which further reacted to form more complex compounds and eventually result in life. Alternative theories of an autotrophic origin of life contradict this theory.

The theory of a chemical origin of life beginning with heterotrophic life was first proposed in 1924 by Alexander Ivanovich Oparin, and eventually published "The Origin of Life." It was independently proposed for the first time in English in 1929 by John Burdon Sanderson Haldane. While these authors agreed on the gasses present and the progression of events to a point, Oparin championed a progressive complexity of organic matter prior to the formation of cells, while Haldane had more considerations about the concept of genes as units of heredity and the possibility of light playing a role in chemical synthesis ( autotrophy).

Evidence grew to support this theory in 1953, when Stanley Miller's conducted an experiment in which he added gasses that were thought to be present on early Earth - water (H ₂O), methane (CH ₄), ammonia (NH ₃), and hydrogen (H ₂) - to a flask and stimulated them with electricity that resembled lightning present on early Earth. The experiment resulted in the discovery that early Earth conditions were supportive of the production of amino acids, with recent re-analyses of the data recognizing that over 40 different amino acids were produced, including several not currently used by life. This experiment heralded the beginning of the field of synthetic prebiotic chemistry, and is now known as the Miller-Urey experiment.

On early Earth, oceans and shallow waters were rich with organic molecules that could have been used by primitive heterotrophs. This method of obtaining energy was energetically favorable until organic carbon became more scarce than inorganic carbon, providing a potential evolutionary pressure to become autotrophic. Following the evolution of autotrophs, heterotrophs were able to utilize them as a food source instead of relying on the limited nutrients found in their environment. Eventually, autotrophic and heterotrophic cells were engulfed by these early heterotrophs and formed a symbiotic relationship. The endosymbiosis of autotrophic cells is suggested to have evolved into the chloroplasts while the endosymbiosis of smaller heterotrophs developed into the mitochondria, allowing the differentiation of tissues and development into multicellularity. This advancement allowed the further diversification of heterotrophs. Today, many heterotrophs and autotrophs also utilize mutualistic relationships that provide needed resources to both organisms. One example of this is the mutualism between corals and algae, where the former provides protection and necessary compounds for photosynthesis while the latter provides oxygen.

However this hypothesis is controversial as CO ₂ was the main carbon source at the early Earth, suggesting that early cellular life were autotrophs that relied upon inorganic substrates as an energy source and lived at alkaline hydrothermal vents or acidic geothermal ponds. Simple biomolecules transported from space was considered to have been either too reduced to have been fermented or too heterogeneous to support microbial growth. Heterotrophic microbes likely originated at low H ₂ partial pressures. Bases, amino acids, and ribose are considered to be the first fermentation substrates.

Heterotrophs are currently found in each domain of life: Bacteria, Archaea, and Eukarya. Domain Bacteria includes a variety of metabolic activity including photoheterotrophs, chemoheterotrophs, organotrophs, and heterolithotrophs. Within Domain Eukarya, kingdoms Fungi and Animalia are entirely heterotrophic, though most fungi absorb nutrients through their environment. Most organisms within Kingdom Protista are heterotrophic while Kingdom Plantae is almost entirely autotrophic, except for myco-heterotrophic plants. Lastly, Domain Archaea varies immensely in metabolic functions and contains many methods of heterotrophy.

Many heterotrophs are chemoorganoheterotrophs that use organic carbon (e.g. glucose) as their carbon source, and organic chemicals (e.g. carbohydrates, lipids, proteins) as their electron sources. Heterotrophs function as consumers in food chain: they obtain these nutrients from saprotrophic, parasitic, or holozoic nutrients. They break down complex organic compounds (e.g., carbohydrates, fats, and proteins) produced by autotrophs into simpler compounds (e.g., carbohydrates into glucose, fats into fatty acids and glycerol, and proteins into amino acids). They release the chemical energy of nutrient molecules by oxidizing carbon and hydrogen atoms from carbohydrates, lipids, and proteins to carbon dioxide and water, respectively.

They can catabolize organic compounds by respiration, fermentation, or both. Fermenting heterotrophs are either facultative or obligate anaerobes that carry out fermentation in low oxygen environments, in which the production of ATP is commonly coupled with substrate-level phosphorylation and the production of end products (e.g. alcohol, CO ₂, sulfide). These products can then serve as the substrates for other bacteria in the anaerobic digest, and be converted into CO ₂ and CH ₄, which is an important step for the carbon cycle for removing organic fermentation products from anaerobic environments. Heterotrophs can undergo respiration, in which ATP production is coupled with oxidative phosphorylation. This leads to the release of oxidized carbon wastes such as CO ₂ and reduced wastes like H ₂O, H ₂S, or N ₂O into the atmosphere. Heterotrophic microbes' respiration and fermentation account for a large portion of the release of CO ₂ into the atmosphere, making it available for autotrophs as a source of nutrient and plants as a cellulose synthesis substrate.

Respiration in heterotrophs is often accompanied by mineralization, the process of converting organic compounds to inorganic forms. When the organic nutrient source taken in by the heterotroph contains essential elements such as N, S, P in addition to C, H, and O, they are often removed first to proceed with the oxidation of organic nutrient and production of ATP via respiration. S and N in organic carbon source are transformed into H ₂S and NH ₄⁺ through desulfurylation and deamination, respectively. Heterotrophs also allow for dephosphorylation as part of decomposition. The conversion of N and S from organic form to inorganic form is a critical part of the nitrogen and sulfur cycle. H ₂S formed from desulfurylation is further oxidized by lithotrophs and phototrophs while NH ₄⁺ formed from deamination is further oxidized by lithotrophs to the forms available to plants. Heterotrophs' ability to mineralize essential elements is critical to plant survival.

Most opisthokonts and prokaryotes are heterotrophic; in particular, all animals and fungi are heterotrophs. Some animals, such as corals, form symbiotic relationships with autotrophs and obtain organic carbon in this way. Furthermore, some parasitic plants have also turned fully or partially heterotrophic, while carnivorous plants consume animals to augment their nitrogen supply while remaining autotrophic.

Animals are classified as heterotrophs by ingestion, fungi are classified as heterotrophs by absorption.

1. "How Cells Harvest Energy" (PDF). McGraw-Hill Higher Education. Archived from the original (PDF) on 2012-07-31.

2. ^ Lwoff, A.; C.B. van Niel; P.J. Ryan; E.L. Tatum (1946). Nomenclature of nutritional types of microorganisms (PDF). Cold Spring Harbor Symposia on Quantitative Biology. Vol. XI (5th ed.). Cold Spring Harbor, N.Y.: The Biological Laboratory. pp. 302-303. Archived (PDF) from the original on 2017-11-07.

3. ^ Wetzel, R.G. (2001). Limnology: Lake and river ecosystems (3rd ed.). Academic Press. p. 700.

4. "The purpose of saprotrophs and their internal nutrition, as well as the main two types of fungi that are most often referred to, as well as describes, visually, the process of saprotrophic nutrition through a diagram of hyphae, referring to the Rhizobium on damp, stale whole-meal bread or rotting fruit." ^ Advanced Biology Principles, p 296.[full citation needed ]

5. ^ Mills, A.L. (1997). The Environmental Geochemistry of Mineral Deposits: Part A: Processes, Techniques, and Health Issues Part B: Case Studies and Research Topics (PDF). Society of Economic Geologists. pp. 125-132. ISBN 978-1-62949-013-7.

6. ^ Miroshnichenko, M.L.; L'Haridon, S.; Jeanthon, C.; Antipov, A.N.; Kostrikina, N.A.; Tindall, B.J.; et al. (1 May 2003). "Oceanithermus profundus gen. nov., sp. nov., a thermophilic, microaerophilic, facultatively chemolithoheterotrophic bacterium from a deep-sea hydrothermal vent". International Journal of Systematic and Evolutionary Microbiology. 53 (3): 747-752. doi:10.1099/ijs.0.02367-0. PMID 12807196.

7. ^ Liang, Yanna (July 2009). "Biomass and lipid productivities of Chlorella vulgaris under autotrophic, heterotrophic and mixotrophic growth conditions". Biotechnology Letters. 31 (7): 1043-1049. doi:10.1007/s10529-009-9975-7. PMID 19322523. S2CID 1989922.

8. ^ Lazcano, Antonio (2015), "Primordial Soup", in Gargaud, Muriel; Irvine, William M.; Amils, Ricardo; Cleaves, Henderson James (eds.), Encyclopedia of Astrobiology, Berlin, Heidelberg: Springer Berlin Heidelberg, pp. 2010-2014, Bibcode:2015enas.book.2010L, doi:10.1007/978-3-662-44185-5_1275, ISBN 978-3-662-44184-8

9. ^ Schönheit, Peter; Buckel, Wolfgang; Martin, William F. (2016). "On the Origin of Heterotrophy". Trends in Microbiology. 24 (1): 12-25. doi:10.1016/j.tim.2015.10.003. PMID 26578093.

10. ^ Haldane, J.B.S. (1929) The Origin of Life. The Rationalist Annual, 3, 3-10.

11. Preiner, Martina; Asche, Silke; Becker, Sidney; Betts, Holly C.; Boniface, Adrien; Camprubi, Eloi; Chandru, Kuhan; Erastova, Valentina; Garg, Sriram G.; Khawaja, Nozair; Kostyrka, Gladys (2020-02-26). "The Future of Origin of Life Research: Bridging Decades-Old Divisions". Life. 10 (3): 20. doi:10.3390/life10030020. ISSN 2075-1729. PMC . PMID 32110893.

12. ^ Jordan, Carl F (2022), "A Thermodynamic View of Evolution", Evolution from a Thermodynamic Perspective, Cham: Springer International Publishing, pp. 157-199, doi:10.1007/978-3-030-85186-6_12, ISBN 978-3-030-85185-9

13. Taylor, D. L.; Bruns, T. D.; Leake, J. R.; Read, D. J. (2002), "Mycorrhizal Specificity and Function in Myco-heterotrophic Plants", Ecological Studies, Berlin, Heidelberg: Springer Berlin Heidelberg, pp. 375-413, doi:10.1007/978-3-540-38364-2_15, ISBN 978-3-540-00204-8

14. ^ Wade, Bingle (2016). MICB 201: Introductory Environmental Microbiology. pp. 236-250.

15. ^ Kirchman, David L. (2014). Processes in Microbial Ecology. Oxford: Oxford University Press. pp. 79-98. ISBN 9780199586936.

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A heterotroph (; from Ancient Greek 'other', and 'nutrition') is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but not producers.

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An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide, generally using energy from light ( photosynthesis) or inorganic chemical reactions ( chemosynthesis). They convert an abiotic source of energy (e.g. light) into energy stored in organic compounds, which can be used by other organisms (e.g. heterotrophs). Autotrophs do not need a living source of carbon or energy and are the producers in a food chain, such as plants on land or algae in water (in contrast to heterotrophs as consumers of autotrophs or other heterotrophs). Autotrophs can reduce carbon dioxide to make organic compounds for biosynthesis and as stored chemical fuel. Most autotrophs use water as the reducing agent, but some can use other hydrogen compounds such as hydrogen sulfide.

The primary producers can convert the energy in the light ( phototroph and photoautotroph) or the energy in inorganic chemical compounds ( chemotrophs or chemolithotrophs) to build organic molecules, which is usually accumulated in the form of biomass and will be used as carbon and energy source by other organisms (e.g. heterotrophs and mixotrophs). The photoautotrophs are the main primary producers, converting the energy of the light into chemical energy through photosynthesis, ultimately building organic molecules from carbon dioxide, an inorganic carbon source. Examples of chemolithotrophs are some archaea and bacteria (unicellular organisms) that produce biomass from the oxidation of inorganic chemical compounds, these organisms are called chemoautotrophs, and are frequently found in hydrothermal vents in the deep ocean. Primary producers are at the lowest trophic level, and are the reasons why Earth sustains life to this day.

Most chemoautotrophs are lithotrophs, using inorganic electron donors such as hydrogen sulfide, hydrogen gas, elemental sulfur, ammonium and ferrous oxide as reducing agents and hydrogen sources for biosynthesis and chemical energy release. Autotrophs use a portion of the ATP produced during photosynthesis or the oxidation of chemical compounds to reduce to NADPH to form organic compounds.

The term autotroph was coined by the German botanist Albert Bernhard Frank in 1892.[non-primary source needed ] It stems from the ancient Greek word ( trophḗ), meaning "nourishment" or "food". The first autotrophic organism developed about 2 billion years ago. Photoautotrophs evolved from heterotrophic bacteria by developing photosynthesis. The earliest photosynthetic bacteria used hydrogen sulphide. Due to the scarcity of hydrogen sulphide, some photosynthetic bacteria evolved to use water in photosynthesis, leading to cyanobacteria.

Some organisms rely on organic compounds as a source of carbon, but are able to use light or inorganic compounds as a source of energy. Such organisms are mixotrophs. An organism that obtains carbon from organic compounds but obtains energy from light is called a photoheterotroph, while an organism that obtains carbon from organic compounds and energy from the oxidation of inorganic compounds is termed a chemolithoheterotroph.

Evidence suggests that some fungi may also obtain energy from ionizing radiation: Such radiotrophic fungi were found growing inside a reactor of the Chernobyl nuclear power plant.

There are many different types of primary producers out in the Earth's ecosystem at different states. Fungi and other organisms that gain their biomass from oxidizing organic materials are called decomposers and are not primary producers. However, lichens located in tundra climates are an exceptional example of a primary producer that, by mutualistic symbiosis, combine photosynthesis by algae (or additionally nitrogen fixation by cyanobacteria) with the protection of a decomposer fungus. Also, plant-like primary producers (trees, algae) use the sun as a form of energy and put it into the air for other organisms. There are of course H2O primary producers, including a form of bacteria, and phytoplankton. As there are many examples of primary producers, two dominant types are coral and one of the many types of brown algae, kelp.

Gross primary production occurs by photosynthesis. This is also a main way that primary producers take energy and produce/release it somewhere else. Plants, coral, bacteria, and algae do this. During photosynthesis, primary producers take energy from the sun and produce it into energy, sugar, and oxygen. Primary producers also need energy to convert this same energy elsewhere, so they get it from nutrients. One type of nutrient is nitrogen.

Without primary producers, organisms that are capable of producing energy on their own, the biological systems of Earth would be unable to sustain themselves. Plants, along with other primary producers, produce the energy that other living beings consume, and the oxygen that they breathe. It is thought that the first organisms on Earth were primary producers located on the ocean floor.

Autotrophs are fundamental to the food chains of all ecosystems in the world. They take energy from the environment in the form of sunlight or inorganic chemicals and use it to create fuel molecules such as carbohydrates. This mechanism is called primary production. Other organisms, called heterotrophs, take in autotrophs as food to carry out functions necessary for their life. Thus, heterotrophs - all animals, almost all fungi, as well as most bacteria and protozoa - depend on autotrophs, or primary producers, for the raw materials and fuel they need. Heterotrophs obtain energy by breaking down carbohydrates or oxidizing organic molecules (carbohydrates, fats, and proteins) obtained in food. Carnivorous organisms rely on autotrophs indirectly, as the nutrients obtained from their heterotrophic prey come from autotrophs they have consumed.

Most ecosystems are supported by the autotrophic primary production of plants and cyanobacteria that capture photons initially released by the sun. Plants can only use a fraction (approximately 1%) of this energy for photosynthesis.[11] The process of photosynthesis splits a water molecule ( ), releasing oxygen ( ) into the atmosphere, and reducing carbon dioxide ( ) to release the hydrogen atoms that fuel the metabolic process of primary production. Plants convert and store the energy of the photon into the chemical bonds of simple sugars during photosynthesis. These plant sugars are polymerized for storage as long-chain carbohydrates, including other sugars, starch, and cellulose; glucose is also used to make fats and proteins. When autotrophs are eaten by heterotrophs, i.e., consumers such as animals, the carbohydrates, fats, and proteins contained in them become energy sources for the heterotrophs.[12] Proteins can be made using nitrates, sulfates, and phosphates in the soil.[13][14]

Primary production in tropical streams and rivers

Aquatic algae are a significant contributor to food webs in tropical rivers and streams. This is displayed by net primary production, a fundamental ecological process that reflects the amount of carbon that is synthesized within an ecosystem. This carbon ultimately becomes available to consumers. Net primary production displays that the rates of in-stream primary production in tropical regions are at least an order of magnitude greater than similar temperate systems.

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An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide, generally using energy from light ( photosynthesis) or inorganic chemical reactions ( chemosynthesis). They convert an abiotic source of energy (e.g.

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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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Products of Photosynthesis = Reactants of Cellular Respiration 

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Products of Photosynthesis = Reactants of Cellular Respiration 

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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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Nobelprize.org, The Official Web Site of the Nobel Prize

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The Law of Conservation of Matter - Conservation of Mass The law of conservation of matter or principle of matter conservation states that the mass of an object or collection of objects never changes over time, no matter how the constituent parts rearrange themselves. The mass can neither be created nor destroyed.

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Conversion of Light Energy to Chem. energy

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Conversion of Light Energy to Chem. energy

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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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http://www2.sluh.org/bioweb/bi100/tutorials/photosynthesis.htm

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Index
Equation for Psyn | ATP | ATP to ADP | Light and Dark Reaction
Simple Psyn Summary | Plant Cell | Chloroplast | Chloroplast Reactions
Psyn and Light | Chlorophyll | Thylakoid Magnified | The Light Reaction
Light Reaction Animated | The Dark Reaction | Dark Reaction Animated
Psyn Animated | Plant Cell Summary | Quiz

Copyright © Steve Kuensting, 2004, All Rights Reserved.

This web tutorial may not be distributed by any means

without the expressed permission of the author!

Introduction
All life forms require a constant source of energy for survival. Cells are constantly in a state of activity - reproduction, growth, maintenance & repair - and a constant source of energy is needed to sustain the activity. Food provides this energy. Food contains chemicals which store energy, and cells break down food chemicals for their energy.

Basically, there are two types of organisms on this planet.
Autotrophs vs Heterotrophs
AUTOTROPHS are organisms that can make food molecules from light or other energy sources. HETEROTROPHS are organisms that cannot make their own food and so must eat other organisms to stay alive. The autotrophs include the plants - grass, trees, shrubs, weeds, - and alga - the green slime found in rivers and ponds. The heterotrophs include all of the animals - snakes, fish, crickets, worms, jellyfish - and many microscopic animals.

Ultimately, the source of all food on this planet is autotrophs. Plants use light energy to produce food chemicals, and the light energy is thus stored in the bonds of the food molecules. Plants and animals use this stored bond energy as fuel for their cells. If the sun stopped radiating light, first the autotrophic plants would die, followed by all of the heterotrophic animals. Those animals that fed on plants would die first, followed by the predators that ate the plant-eating animals. Eventually, all life on the planet would cease.
Photosynthesis vs. the Food Chain

Importance of the Sun
Thus, anything you ever did was made possible by the trapped solar energy of the food chemicals you ate. The process that makes these food chemicals using solar energy is PHOTOSYNTHESIS.
Defined, photosynthesis is: - chemical reactions that convert the radiant energy of sunlight to chemical energy of sugars.

Equation for Photosynthesis
Photosynthesis is a very complex process. It involves many different chemical reactions that occur in a pathway or series, that is, one chemical reaction produces what the next chemical reaction needs. A chemical equation is written below which summarizes the reactants and products of the photosynthesis pathway. The equation shows that carbon dioxide and water are used with light energy to produce glucose sugar and oxygen gas.

History of Photosynthesis Research

One of the first records of research is attributed to a Dutch scientist named Jan Baptist van Helmont, dating back to 1648. In trying to determine where plants gained their mass, he weighed and planted a willow sprig in a known amount of potted soil and grew it for 5 years. At the end of the experiment, he re-weighed the soil and weighed the tree. The willow shoot started at 2.3 kg and the soil originally weighed 90.8 kg. After 5 years, the plant reached 76.8 kg while the soil only lost 56 GRAMS. Van Helmont concluded that the willow tree had gained 74 kg from the water that had nourished it for the duration of the 5 year experiment.

History of Photosynthesis Research

In 1771, an English Scientist named Joseph Priestley discovered that plants and animals alter the air around them in complementary ways. He burned a candle in a covered jar until it burned out. If a plant was in the jar, after several days the candle would relight. He repeated the same experiment with a mouse - a mouse with a plant in the jar would live while a mouse in a jar alone would die. Priestley concluded that the plants were restoring the air that had been "injured" by the candle or mouse.

History of Photosynthesis Research
In 1779, a Dutch physician named Jan Ingenhousz discovered that submerged willow sprigs produced oxygen gas only in the presence of sunlight. By 1796, after further research, Ingenhousz was able to write the first equation for photosynthesis, which was:

Light is not directly usable in photosynthesis. It cannot be directly used to combine carbon dioxide and water to form sugar and oxygen gas. It is first converted to a more usable form. The light is absorbed in photosynthesis and temporarily stored in a versatile molecule called adenosine triphosphate or ATP. ATP can then be used to combine carbon dioxide and water to form sugar and oxygen.

ATP
ATP is a molecule which consists of three smaller types of molecules: 1) adenine, 2) ribose, 3) phosphates. One ATP molecule consists of one adenine, one ribose, and three phosphates bonded together. It is picured below. The wavy lines between the phosphates represent high energy bonds.

Most of the chemical energy of ATP is stored in the bond between the 2nd and 3rd phosphates. When the energy of ATP is used to make glucose, the third phosphate is broken off and attached to another molecule, thus transferring the energy from the ATP to the other molecule. This transfer of the phosphate to another molecule is called PHOSPHORYLATION. Since the ATP has lost one phosphate, it is now called adenosine diphosphate, or ADP. It is drawn below.

ATP to ADP
Photosynthesis must constantly make more ATP by restoring ADP molecules. It does this by bonding phosphate molecules to the 2nd phosphate of ADP, thus converting it back to ATP, by USING LIGHT ENERGY. The ATP would then be ready to be used again to make sugar. ATP is involved in other chemical reactions, such as respiration, which will be covered in a later program.

Photosynthesis converts moving radiant energy into stored chemical bond energy. The chemical equation is written below which summarizes the chemical reactions of photosynthesis. Photosynthesis is actually much more complex than what is represented by the equation below.

The complex process of photosynthesis actually consists of TWO interrelated complex reactions -- the LIGHT and DARK reactions.
In the light reactions, light energy is converted into the chemical energy of ATP, while water is broken down for its hydrogen atoms. The ATP and hydrogen atoms are fed to the dark reaction which uses them to produce glucose sugar from carbon dioxide. Ultimately the light energy ends up in the glucose, but it does not get their easily.

Plant Cell
Photosynthesis takes place only in green plant parts such as leaves and some stems, not in roots. In leaf cells, small green organelles called chloroplasts can be seen with the aid of a microscope. These chloroplasts are what color the leaf green and they are the site of photosynthesis. The only part of a plant cell that can participate in photosynthesis is the chloroplast.

Chloroplast
Below is a chloroplast magnified to see its internal parts. Within a chloroplast there are small disks called thylakoids. The thylakloids are located in stacks, like stacks of pennies, which are called grana. The fluid outside of the thylakloids is called the stroma.

ANIMATIONS OF THE LIGHT REACTION
Remember, the purpose of the light reaction was to produce ATP and H atoms for the dark reaction. The electron pumping of the light reaction makes this possible, by pumping H ions into the thylakoid interior which are used to make ATP, and by NADP picking up the electrons and H ions to carry them to the dark reaction.
In the following animation, the light reaction is shown in operation. The first frame is show below.

Light Reaction Animation

Download/Play Simple Gif Animations: Slow | Medium | Fast

The animations are Copyright © 1989, Steve Kuensting, All Rights Reserved.

The Dark Reaction Animated
In the following animation, the dark reaction is shown in operation. Below is the first frame of the animation.

Dark Reaction Animation

Download/Play Simple Gif Animations: Slow | Medium | Fast

The animations are Copyright © 1989, Steve Kuensting, All Rights Reserved.

Photosynthesis Animated
In the next and final animation, the dark and light reaction are shown occurring simultaneously. The production of only a single glucose molecules is shown. The animation is complex because of so many interrelated processes occurring simultaneously. Try and watch only one portion at a time to see what is going on in that area only. Below is the starting frame of the animation.

Below are many of the symbols that are used in the animation to simplify the process. Study them before going on to view the animation using the three hyperlinks below.

Photosynthesis Animation

Download/Play Simple Gif Animations: Slow | Medium | Fast

The animations are Copyright © 1989, Steve Kuensting, All Rights Reserved.

So, the light reaction only exists to power the dark reaction where the sugar is actually made. The oxygen made in the light reaction is released into the air -- all the oxygen you ever breathed was from a leaf or aglae somewhere. The whole process is truly complex, with many more steps than are actually listed. Enzymes are used for every chemical reaction involved in the process.

Quiz

1. What is the name of the process by which plants chemically store solar energy?

2. What molecule is the source of electrons in the light reaction?

3. What is the energy source that powers the light reaction?

4. What molecule is produced as waste in the light reaction?

5. What gaseous molecule is used by the dark reaction to build glucose?

6. What atoms are carried to the dark reaction from the light reaction?

7. What molecule carries trapped light energy to the dark reaction?

8. What term broadly describes all organisms that can photosynthesize?

9. Light energy is converted to ____________ energy in photosynthesis. (fill in the blank)

10. What green pigment is found in chloroplasts?

11. What colors of light does chlorophyll not absorb?

12. What are the small disks called that are found in a chloroplast?

13. What is the fluid called that lies outside the grana of a chloroplast?

14. Inside of a chloroplast, on what small structures do the light reactions occur?

15. Inside of a chloroplast, where do the dark reactions occur?

16. What 5-carbon molecule reacts with carbon dioxide in the dark reaction?

17. What molecule carries hydrogen atoms from the light reaction to the dark reaction?

18. What is the name of the process of ATP production by use of hydrogen ions?

19. How many glucose molecules are produced from 6RuBP and 6 carbon dioxide molecules completely reacting in the dark reaction?

20. To what molecule is PGA converted by the use of ATP and hydrogen ions?

21. What molecule is recycled in the dark reaction?

22. To what molecules is ATP broken down by its use in the dark reaction?

23. In what organelle does photosynthesis occur?

24. Ultimately, what is the source of all biological energy on earth?

25. How many different TYPES of molecules are found in an ATP molecule?

26. Who discovered the steps of the dark reaction?

27. How many molecules of carbon dioxide are required to make 1 glucose in photosynthesis?

28. How many water molecules are required to make one glucose in photosynthesis? (don't count water made in dark rx)

29. How many oxygen molecules are made in the production of 1 glucose in photosynthesis?

30. What is another name for the dark reaction?

Diagram - Name the following photosynthesis molecules or structures.

Answers

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Index Equation for Psyn | ATP | ATP to ADP | Light and Dark Reaction Simple Psyn Summary | Plant Cell | Chloroplast | Chloroplast Reactions Psyn and Light | Chlorophyll | Thylakoid Magnified | The Light Reaction Light Reaction Animated | The Dark Reaction | Dark Reaction Animated Psyn Animated | Plant Cell Summary | Quiz Copyright © Steve Kuensting, 2004, All Rights Reserved.

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Chloroplasts are the food producers of the cell. The organelles are only found in plant cells and some protists such as algae. Animal cells do not have chloroplasts. Chloroplasts work to convert light energy of the Sun into sugars that can be used by cells. The entire process is called photosynthesis and it all depends on the little green chlorophyll molecules in each chloroplast.

Plants are the basis of all life on Earth. They are classified as the producers of the world. In the process of photosynthesis, plants create sugars and release oxygen (O ₂). The oxygen released by the chloroplasts is the same oxygen you breathe every day. Mitochondria work in the opposite direction. They use oxygen in the process of releasing chemical energy from sugars.

We'll hit the high points for the structure of a chloroplast. Two membranes contain and protect the inner parts of the chloroplast. They are appropriately named the outer and inner membranes. The inner membrane surrounds the stroma and the grana (stacks of thylakoids). One thylakoid stack is called a granum.

Chlorophyll molecules sit on the surface of each thylakoid and capture light energy from the Sun. As energy rich molecules are created by the light-dependent reactions, they move to the stroma where carbon (C) can be fixed and sugars are synthesized.

The stacks of thylakoid sacs are connected by stroma lamellae. The lamellae act like the skeleton of the chloroplast, keeping all of the sacs a safe distance from each other and maximizing the efficiency of the organelle. If all of the thylakoids were overlapping and bunched together, there would not be an efficient way to capture the Sun's energy.

The purpose of the chloroplast is to make sugars that feed the cell's machinery. Photosynthesis is the process of a plant taking energy from the Sun and creating sugars. When the energy from the Sun hits a chloroplast and the chlorophyll molecules, light energy is converted into the chemical energy found in compounds such as ATP and NADPH.

Those energy-rich compounds move into the stroma where enzymes fix the carbon atoms from carbon dioxide (CO ₂). The molecular reactions eventually create sugar and oxygen (O ₂). Plants and animals then use the sugars ( glucose) for food and energy. Animals also breathe the oxygen gas that is released.

Not all chlorophyll is the same. Several types of chlorophyll can be involved in photosynthesis. You will hear about chlorophyll a and b most often. All chlorophylls are varieties of green and have a common chemical structure called a porphyrin ring.

There are other molecules that are also photosynthetic. One day you might hear about carotenoids in carrots, phycocyanin in bacteria, phycoerythrin in algae, or fucoxanthin in brown algae. While these compounds might be involved in photosynthesis, they are not all green or the same structure as chlorophyll. Accessory pigments such as carotenoids and fucoxanthin pass absorbed light energy to neighboring chlorophyll molecules instead of using it themselves.

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Chloroplasts are the food producers of the cell. The organelles are only found in plant cells and some protists such as algae. Animal cells do not have chloroplasts. Chloroplasts work to convert light energy of the Sun into sugars that can be used by cells.

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Diagram of the process of photosynthesis, showing the light reactions and the Calvin cycle

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Discover this and millions of other royalty-free stock photos, illustrations, and vectors in the Shutterstock collection. Thousands of new, high-quality images added every day.

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(Image credit: KPG_Payless | Shutterstock)

Photosynthesis is the process used by plants, algae and certain bacteria to harness energy from sunlight and turn it into chemical energy. Here, we describe the general principles of photosynthesis and highlight how scientists are studying this natural process to help develop clean fuels and sources of renewable energy.

Types of photosynthesis

There are two types of photosynthetic processes: oxygenic photosynthesis and anoxygenic photosynthesis. The general principles of anoxygenic and oxygenic photosynthesis are very similar, but oxygenic photosynthesis is the most common and is seen in plants, algae and cyanobacteria.

During oxygenic photosynthesis, light energy transfers electrons from water (H ₂O) to carbon dioxide (CO ₂), to produce carbohydrates. In this transfer, the CO ₂ is "reduced," or receives electrons, and the water becomes "oxidized," or loses electrons. Ultimately, oxygen is produced along with carbohydrates.

Oxygenic photosynthesis functions as a counterbalance to respiration by taking in the carbon dioxide produced by all breathing organisms and reintroducing oxygen to the atmosphere.

On the other hand, anoxygenic photosynthesis uses electron donors other than water. The process typically occurs in bacteria such as purple bacteria and green sulfur bacteria, which are primarily found in various aquatic habitats.

"Anoxygenic photosynthesis does not produce oxygen - hence the name," said David Baum, professor of botany at the University of Wisconsin-Madison. "What is produced depends on the electron donor. For example, many bacteria use the bad-eggs-smelling gas hydrogen sulfide, producing solid sulfur as a byproduct."

Though both types of photosynthesis are complex, multistep affairs, the overall process can be neatly summarized as a chemical equation.

Oxygenic photosynthesis is written as follows:

Here, six molecules of carbon dioxide (CO ₂) combine with 12 molecules of water (H ₂O) using light energy. The end result is the formation of a single carbohydrate molecule (C ₆H ₁₂O ₆, or glucose) along with six molecules each of breathable oxygen and water.

Similarly, the various anoxygenic photosynthesis reactions can be represented as a single generalized formula:

The letter A in the equation is a variable and H ₂A represents the potential electron donor. For example, A may represent sulfur in the electron donor hydrogen sulfide (H ₂S), explained Govindjee and John Whitmarsh, plant biologists at the University of Illinois at Urbana-Champaign, in the book " Concepts in Photobiology: Photosynthesis and Photomorphogenesis" (Narosa Publishers and Kluwer Academic, 1999).

(Image credit: Shutterstock)

The photosynthetic apparatus

The following are cellular components essential to photosynthesis.
Pigments
Pigments are molecules that bestow color on plants, algae and bacteria, but they are also responsible for effectively trapping sunlight. Pigments of different colors absorb different wavelengths of light. Below are the three main groups.

Chlorophylls: These green-colored pigments are capable of trapping blue and red light. Chlorophylls have three subtypes, dubbed chlorophyll a, chlorophyll b and chlorophyll c. According to Eugene Rabinowitch and Govindjee in their book "Photosynthesis"(Wiley, 1969), chlorophyll a is found in all photosynthesizing plants. There is also a bacterial variant aptly named bacteriochlorophyll, which absorbs infrared light. This pigment is mainly seen in purple and green bacteria, which perform anoxygenic photosynthesis.

Carotenoids: These red, orange or yellow-colored pigments absorb bluish-green light. Examples of carotenoids are xanthophyll (yellow) and carotene (orange) from which carrots get their color.

Phycobilins: These red or blue pigments absorb wavelengths of light that are not as well absorbed by chlorophylls and carotenoids. They are seen in cyanobacteria and red algae.

Plastids
Photosynthetic eukaryotic organisms contain organelles called plastids in their cytoplasm. The double-membraned plastids in plants and algae are referred to as primary plastids, while the multiple-membraned variety found in plankton are called secondary plastids, according to an articlein the journal Nature Education by Cheong Xin Chan and Debashish Bhattacharya, researchers at Rutgers University in New Jersey.

Plastids generally contain pigments or can store nutrients. Colorless and nonpigmented leucoplasts store fats and starch, while chromoplasts contain carotenoids and chloroplasts contain chlorophyll, as explained in Geoffrey Cooper's book, " The Cell: A Molecular Approach" (Sinauer Associates, 2000).

Photosynthesis occurs in the chloroplasts; specifically, in the grana and stroma regions. The grana is the innermost portion of the organelle; a collection of disc-shaped membranes, stacked into columns like plates. The individual discs are called thylakoids. It is here that the transfer of electrons takes place. The empty spaces between columns of grana constitute the stroma.

Chloroplasts are similar to mitochondria, the energy centers of cells, in that they have their own genome, or collection of genes, contained within circular DNA. These genes encode proteins essential to the organelle and to photosynthesis. Like mitochondria, chloroplasts are also thought to have originated from primitive bacterial cells through the process of endosymbiosis.

"Plastids originated from engulfed photosynthetic bacteria that were acquired by a single-celled eukaryotic cell more than a billion years ago," Baum told Live Science. Baum explained that the analysis of chloroplast genes shows that it was once a member of the group cyanobacteria, "the one group of bacteria that can accomplish oxygenic photosynthesis."

In their 2010 article, Chan and Bhattacharya make the point that the formation of secondary plastids cannot be well explained by endosymbiosis of cyanobacteria, and that the origins of this class of plastids are still a matter of debate.
Antennae
Pigment molecules are associated with proteins, which allow them the flexibility to move toward light and toward one another. A large collection of 100 to 5,000 pigment molecules constitutes "antennae," according to an article by Wim Vermaas, a professor at Arizona State University. These structures effectively capture light energy from the sun, in the form of photons.

Ultimately, light energy must be transferred to a pigment-protein complex that can convert it to chemical energy, in the form of electrons. In plants, for example, light energy is transferred to chlorophyll pigments. The conversion to chemical energy is accomplished when a chlorophyll pigment expels an electron, which can then move on to an appropriate recipient.
Reaction centers
The pigments and proteins, which convert light energy to chemical energy and begin the process of electron transfer, are known as reaction centers.

The photosynthetic process

The reactions of plant photosynthesis are divided into those that require the presence of sunlight and those that do not. Both types of reactions take place in chloroplasts: light-dependent reactions in the thylakoid and light-independent reactions in the stroma.

Light-dependent reactions (also called light reactions): When a photon of light hits the reaction center, a pigment molecule such as chlorophyll releases an electron.

"The trick to do useful work, is to prevent that electron from finding its way back to its original home," Baum told Live Science. "This is not easily avoided, because the chlorophyll now has an 'electron hole' that tends to pull on nearby electrons."

The released electron manages to escape by traveling through an electron transport chain, which generates the energy needed to produce ATP (adenosine triphosphate, a source of chemical energy for cells) and NADPH. The "electron hole" in the original chlorophyll pigment is filled by taking an electron from water. As a result, oxygen is released into the atmosphere.

Light-independent reactions (also called dark reactions and known as the Calvin cycle): Light reactions produce ATP and NADPH, which are the rich energy sources that drive dark reactions. Three chemical reaction steps make up the Calvin cycle: carbon fixation, reduction and regeneration. These reactions use water and catalysts. The carbon atoms from carbon dioxide are "fixed," when they are built into organic molecules that ultimately form three-carbon sugars. These sugars are then used to make glucose or are recycled to initiate the Calvin cycle again.

(Image credit: PNNL, QuickBird satellite)

Photosynthesis in the future

Photosynthetic organisms are a possible means to generate clean-burning fuels such as hydrogen or even methane. Recently, a research group at the University of Turku in Finland, tapped into the ability of green algae to produce hydrogen. Green algae can produce hydrogen for a few seconds if they are first exposed to dark, anaerobic (oxygen-free) conditions and then exposed to light The team devised a way to extend green algae's hydrogen production for up to three days, as reported in their 2018 study published in the journal Energy & Environmental Science.

Scientists have also made advances in the field of artificial photosynthesis. For instance, a group of researchers from the University of California, Berkeley, developed an artificial system to capture carbon dioxide using nanowires, or wires that are a few billionths of a meter in diameter. The wires feed into a system of microbes that reduce carbon dioxide into fuels or polymers by using energy from sunlight. The team published its design in 2015 in the journal Nano Letters.

In 2016, members of this same group published a study in the journal Science that described another artificial photosynthetic system in which specially engineered bacteria were used to create liquid fuels using sunlight, water and carbon dioxide. In general, plants are only able to harness about one percent of solar energy and use it to produce organic compounds during photosynthesis. In contrast, the researchers' artificial system was able to harness 10 percent of solar energy to produce organic compounds.

Continued research of natural processes, such as photosynthesis, aids scientists in developing new ways to utilize various sources of renewable energy. Seeing as sunlight, plants and bacteria are all ubiquitous, tapping into the power of photosynthesis is a logical step for creating clean-burning and carbon-neutral fuels.
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(Image credit: KPG_Payless | Shutterstock) Photosynthesis is the process used by plants, algae and certain bacteria to harness energy from sunlight and turn it into chemical energy. Here, we describe the general principles of photosynthesis and highlight how scientists are studying this natural process to help develop clean fuels and sources of renewable energy.