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Circulation - Cardiac Cycle, Blood Velocity, and Blood Vessel across Sectional Area

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Circulation - Cardiac Cycle, Blood Velocity, and Blood Vessel across Sectional Area

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Explanation:
The nodal tissue within the heart controls the normal heartbeat, which is known as intrinsic control. An impulse is conducted into both atria simultaneously, causing them to contract (atrial systole), thus forcing blood into the ventricles. The impulse then moves to the atrioventricular mode (AVN).

Modification of the Normal Heartbeat:
• modification= speeding up or slowing down
• stimulation by nerve impulses or hormones
A.) Autonomic Regulation of Heartbeat by the Nervous System:
• 2 divisions: sympathetic and parasympathetic
• stimulus: hypotension (low blood pressure)
• receptor: cardiovascular centre of the medulla oblongata
• effector: sympathetic division of autonomic nervous system
• response: increase heart rate/ stronger heartbeat
• stimulus: hypertension (high blood pressure)
• effector: parasympathetic
B.) Hormonal Regulation of Heartbeat by the Endocrine System
• stimulus: low b.p/ hypotension
• receptor: cardiovascular centre of the medulla oblongata
• effector: sympathetic division of autonomic nervous system
• heart: increase heartbeat

Examples:
1. a.) Explain why it is possible for a human heart to continue beating after it has been removed from the human body.
The normal heartbeat is controlled by nodal tissue, which is found within the heart walls.
b.) How could an experimenter increase the rate at which a removed heart beats?
They could stimulate the SA node with electrical impulses or stimulate the SA node with the hormones.

Measuring Blood Pressure:
Blood pressure can be measured by a device called a sphygmomanometer in units of mm of Hg. Two blood pressure values called systolic (ventricle walls contracting) and diastolic (ventricle walls relaxing) are recorded. It's measured at the brachial artery above the elbow and the cuff that is placed around the arm is pumped until no sounds are heard.

Hypertension and Hypotension:
Hypertension is prolonged and abnormally high blood pressure.
Contributing factors:
1. excessive saturated fats/ cholesterol leads to artherscleorosis
(fatty deposits in the arteries restricts blood flow)
2. excessive salt in diet
3. nicotine causes vasoconstriction and increased b.p
4. genetic factors predispose people to high b.p
5. diabetes and kidney disease may lead to hypertension
7. stress and b.p
Hypotension is prolonged and abnormally low blood pressure.
Contributing factors:
1. excessive blood loss = decreased b.p
2. decreased cardiac output= less blood forced through the system
3. leaky heart valves > back flow > less blood through system

So What?
Blood pressure and blood velocity oscillate in arteries due to systole and diastole. Blood pressure and blood velocity decrease due to increased cross-sectional area and increased friction between blood vessel walls and blood. Also, low blood velocity allows time for exchange between blood and tissue/cells.

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Circulation - Heart and Blood Vessel Structure and Function

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Circulation - Heart and Blood Vessel Structure and Function

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Explanation:
The heart is a very muscular organ which lies between the lungs and behind the sternum within the thoracic cavity. The heart is enclosed in the pericardial sac which also holds a small amount of fluid for lubrication.

Heart Chambers:
Two Atria (Left and Right): Thin upper chambers that receive blood returning to the heart through the veins.
Two Ventricles (Left and Right): Thick, muscular lower chambers and receives blood, then pumps blood out of the heart through the arteries.
Septum: Separates the right and left sides of the heart.
Apex: Tip of the heart.

Heart Valves:
Between the atria and ventricles, there are valves called the atrioventricular valves. The AV valve between the right atrium and right ventricle has 3 flaps (tricuspid AV valve). Whereas the AV valve between the left atrium and the left ventricle has 2 flaps (bicuspid AV valve).

Blood Vessels:
1.) Arteries:
• thick, elastic walls
• lumen: holds blood
• 3 layers: outer connective tissues
• middle layer of smooth muscle and elastic fibres (stretch)
• inner endothelium
• allows stretching/ response to large change in pressure
2.) Arterioles:
• carries blood away from heart/ between arteries and capillaries
• vasodilation and vasoconstriction allows vessels to change diameter, affecting blood pressure and heat loss
• 3 layers: middle layer mostly smooth layer
• vasodilation= elastic fibres relaxes= increase in diameter= decrease in blood pressure
3.) Capillaries:
• exchange of nutrients and wastes, oxygen and CO2 via diffusion
• connect arterioles to venules
• one cell thick to facilitate diffusion
• large SA
• highly branched capillary beds increase SA
• sphincters at beginning of some beds regulates blood flow affecting blood pressure and tissues use of nutrients and oxygen
4.) Venules:
• conducts low blood pressure from capillaries to veins
• bigger lumen
• thin walls
• middle later not well developed
• don't need to be thick-walled or elastic
5.) Veins
• carries low-pressure blood towards heart
• act as blood reservoirs
• 3 layers, thin elastic layer due to low b.p
• one way valves prevent backflow of blood

Coronary Blood Vessels:
The blood vessels embedded in the heart's muscular walls are called the coronary blood vessels, which include coronary arteries, capillaries, venules and veins. They also supply the heart tissue with oxygen and nutrients and remove CO2 and wastes.

Examples:
1. a.) Which chamber of the heart has the thickest walls?
The left ventricle.
b.) Explain why this chamber requires such thick walls.
It has to pump blood through the systemic circulatory system which carries the blood throughout the body.

So What?
The purpose of the human circulatory system is to act as the body's main transport system. The heart is important because is acts as the circulatory system's pump. As a result of the heart's muscular walls, blood is forced through the blood vessels which brings it within close proximity to all the body's cells/ tissues. The heart is often described as a dual pump since it forces the blood through both of the body's major circulatory circuits which are known as the systemic and pulmonary circulatory systems.

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Explanation:
Exchange between the blood of the systemic capillaries and the tissues is determined primarily by the following two forces:
1. Blood (hydrostatic) pressure which moves particles such as water, amino acids, glucose, and oxygen from the blood into the tissue/cells.
2. Osmotic pressure of the blood which is created by the presence of CO2 and wastes in the blood and moves small particles such as protein, cells, and platelets from the plasma protein into the blood.

Exchange at the arteriole end of the capillary beds:
Blood Pressure: 40mm Hg
Osmotic Pressure: 25mm Hg
Net Blood Pressure: 15mm Hg
Since blood pressure exceeds osmotic pressure at the arteriole end of the capillary beds, small particles such as water, oxygen, amino acids, and glucose are forced from the blood into the cells/tissues. Particles such as proteins, red blood cells, and platelets are too large to move across the capillary walls and thus remain in the capillary.

Exchange in the middle of capillary beds:
In the middle of capillary beds, blood pressure and osmotic pressure are approximately equal. The movement of small particles across the capillary walls occurrs by diffusion and is therefore determined by the concentration gradient of those particles. Nutrients such as glucose and amino acids and the gas oxygen will diffuse from the blood into the tissue fluid. Wastes and the gas CO2 will diffuse from the tissue fluid into the capillary.

Exchange at the venule end of the capillary beds:
Blood Pressure

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Explanation:
The digestive pathway following the stomach is as follows: the small intestine and the large intestine. The small intestine consists of three regions called the duodenum, jejunum, and ileum.

Duodenum: The duodenum consists of the first 25cm of the small intestine. Ducts from the gallbladder and pancreas join then empty into the duodenum.

Bile: Bile is produced in the liver and stored in the gallbladder. It also contains bile salts which emulsify fat.

Pancreatic Juice: The presence of HCl acid in the acid chyme stimulates the pancreas to release pancreatic juices. It contains NaHCO3 which helps to neutralize the acid chyme, causing the pH of the small intestine to be slightly basic.

Jejunum and Ileum: The jejunum and ileum are the sites of the majority of chemical digestion and absorption. The long length of the jejunum and ileum also provides time for digestion to occur. Its walls

Large Intestine/Colon: At the junction which joins the small intestine to the large intestine, there's a bind sac called the cecum which has an appendix. Furthermore, the colon includes three regions called the ascending colon, the transverse colon, and the descending colon. Moreover, various bacteria such as E. colin live in the colon and help to break down materials that cannot be digested by humans such as cellulose/fibre and produce some vitamins (i.e. Vitamin K) which we absorb and use.

Roles of the Liver:
The liver has a number of functions which include:
1. Removes and metabolizes toxic substances (i.e. alcohol) from the blood.
2. Uses amino acids from the blood to produce proteins (i.e. prothrombin and fibrinogen, which are used in blood clotting).
3. Stores iron and the fat soluble vitamins A, D, K, and B12.
4. Converts the toxic amino acid breakdown product ammonia into urea which is less toxic.

Examples:
1. a.) Name the two digestive enzymes which are classified as proteases.
Trypsin and pepsin.
b.) Explain why these enzymes are classed as proteases.
These enzymes digests long polypeptides into short polypeptides.

So What?:
The small intestine is important because it contains bile (in the duodenum), which helps in preparation for chemical digestion. It also contains pancreatic juice, which has NaHCO3 and helps to neutralize the acid chyme, causing the pH of the small intestine to be slightly basic. Along with their role in chemical digestion, the jejunum and ileum are also the main sites of absorption of nutrients and water from the digestive tract into the blood and lymph. Whereas for the large intestine/colon, all three parts of the colon are involved in the absorption of water, salts, and some vitamins. Lastly, the liver helps to maintain homeostasis in the blood.

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Explanation:
There are two types of digestion: mechanical digestion and chemical digestion. Mechanical digestion is the physical breakdown of food into moderate sized particles. It occurs as a result of the actions of the teeth, tongue, and the muscular walls of the stomach. On the other hand, chemical digestion is the chemical breakdown of food into molecular sized particles due to the action of enzymes secreted into the digestion tract. These particles can then be absorbed into the blood, which will transport them to the cells throughout the body.

Mode of Action of Digestive Enzymes:
1. Mouth: Salivary amylase hydrolyses the starch into maltose.
2. Stomach: Pepsin hydrolyses long p.p's into shorter p.p's.
3. Small intestine: Trypsin hydrolyses long p.p's into shorter p.p's.
4. Small intestine: Pancreatic amylase hydrolyses starch into maltose.
5. Small intestine: Lipase digests neutral fat molecules into one glycerol and 3 fatty acids.
6. Small intestine: Peptidases hydrolyze short p.p's into amino acids.
7. Small intestine: Maltase hydrolyses maltose into molecules of glucose.
8. Small intestine: Nucleases hydrolyze RNA and DNA into nucleotides.

The Digestive Pathway:
1. Mouth: The cavity inside the mouth is called the oral cavity. The tongue also helps to mix food with saliva and has taste buds on its upper surface. Three pairs of salivary glands called the parotid
glands, sublingual glands, and the submandibular glands have ducts which carries saliva into the oral cavity.
2. Pharynx: The pharynx is a muscular passageway which connects the oral cavity with the muscular tube called the esophagus, and is the site of swallowing. During swallowing, the soft palate moves back and closes off the nasopharynx which leads to the nasal cavities. A flap of tissue called the epiglottis also covers the glottis (the opening to the larynx, thus preventing food from entering the larynx. The food is then forced from the pharynx to the esophagus.
3. Esophagus: The esophagus is a muscular tube which conducts food from the pharynx to the stomach. Food is pushed along the esophagus due to peristalsis. At the junction of the esophagus and the stomach is a ring-like muscle called the cardiac sphincter, which prevents the back-flow of food from the stomach into the esophagus by contracting and closing off the entrance to the stomach.
4. Stomach: The stomach is a muscular J-shaped expandable sac which lies in the abdominal cavity just beneath the diaphragm. The walls of the stomach have three layers of smooth muscle which allow the stomach to mix the food with gastric juice. It also has large folds called rugae, which allow the stomach to expand in order to hold a large volume. The lining of the stomach (mucosa) have epithelial goblet cells on its outer surface that secrete mucous and protects the walls from the acidic conditions in the gastric cavity.

Example:
1. Contrast mechanical and chemical digestion. Give at least two differences.
Mechanical digestion: Breakdown of food (physical) and uses teeth/tongue.
Chemical digestion: Absorption of food and uses enzymatic actions.

So what?:
The digestive system is important because it breaks down food containing nutrients into molecular sized particles, which can be absorbed from the digestive tract into the blood cells throughout the body. In particular, mechanical digestion helps to prepare the food for swallowing and increases the surface area of the food in preparation for food digestion by enzymes. Whereas for chemical digestion, it helps in supplying energy and nutrients necessary for cellular activities and growth.

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Explanation:
Most mutations occur during meiosis/mitosis or during cell division. There are also two types of genetic mutations: gene mutations and chromosome mutations. Both mutations can be found in body (somatic) cells and reproductive cells (egg/sperm). However, mutations in somatic cells cannot be passed on to offspring but are passed on when the cell divides, whereas mutations in gamete cells can be passed to offspring, in which case the mutation would exist in every cell of the resulting organism.

A.) Gene Mutations
Gene mutations affect individual genes on a chromosome and involve a change in the gene sequence of one gene and therefore one polypeptide/protein affected. The change will first be reflected in the mRNA and then in the enzyme or other protein that the mRNA codes for (and finally in the appearance of new traits in the living organism)

Types of Gene Mutations:
1.) Point Mutations (Substitution):
It is where one base replaces another in a DNA triplet and may also affect one amino a is in a protein. It may or may not also be serious.
2.) Deletions:
It is where one base is lost from the DNA sequence and affects every triplet (every mRNA codon) after the deletion, which can result in proteins that do not function properly (depends on where deletion occurs).
3.)  Insertion:
It is where one base is added to the DNA sequence and affects every triplet (every mRNA codon) after the insertion, which has the same result as a deletion mutation.

Examples:
Point Mutations:
gene: THE FAT CAT ATE THE RAT
gene: THE FIT CAT ATE THE RAT
Deletions:
gene: THE FAT CAT ATE THE RAT
gene: THE F_TC ATA TET HER (abnormal, nonfunctional protein)
Insertion:
gene: THE FAT CAT ATE THE RAT
gene: THE FAA TCA TAT ETH ERA (abnormal, nonfunctional protein)

So What?
Mutations are important because

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Explanation:
Recombinant DNA technology allows scientists to use enzymes to cut a gene from a chromosome of a particular organism such as a human and to splice (join) it onto the DNA from another organism such as a bacterium. This creates recombinant DNA, which can then be taken up by a bacterial cell which then can make the protein coded for by the gene. The bacterial cell is then cultured, resulting in millions of daughter cells and therefore millions of copies of the original gene (the gene has been cloned). Since all of the bacterial daughter cells have a copy of the gene, they will all be able to produce the protein coded for by that gene. This allows large amount of protein to be produced inexpensively.

Steps in Cloning a Gene using a Bacterial Plasmid:
1. A plasmid is removed from a bacterial cell. A specific restriction endonucleases is used to cleave open the plasmid, creating sticky ends.
2. The desired/target gene is cut out of its chromosome using the same restriction endonucleases that was used to cut open the plasmid. This creates sticky ends which are complementary (will bind) to the sticky ends from the plasmid.
3. The cleaved bacterial plasmid is mixed with the desired gene. With the help of the enzyme DNA ligase, the gene and the cleaved plasmid will be spliced together, creating a recombinant DNA plasmid.
4. The recombinant DNA plasmid is added to the bacterial cell.
5. The bacterial cell with the recombinant DNA is then cultured, producing millions of daughter cells, all of which will have the recombinant DNA with the desired gene.
6. Since each of the daughter cells have a copy of the desired gene, they will be able to produce the protein coded for by that gene.
7. With each of the millions of these bacteria producing a small amount of protein, the total protein production is very high.

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Explanation:
Protein synthesis is the process whereby a sequence of nucleotides on a DNA molecule is translated into a sequence of amino acids (a polypeptide). A gene is a linear segment of DNA nucleotides that codes for the amino acid sequence of one polypeptide. DNA (containing the code for making the polypeptide) cannot leave the nucleus and the organelles (ribosomes) where amino acids are linked together to form the polypeptide are in the cytoplasm. As a result, two steps are required: transcription and translation.

1.  Transcription: The DNA code is "transcribed" (copied) onto a messenger RNA molecule (mRNA), which takes place in the nucleus.

2.  Translation: The mRNA is translated into a polypeptide with the help of ribosomes and transfer RNA (tRNA), which takes place in the cytoplasm. There are three phases of translation: initiation, elongation, and termination.

Initiation: A complex forms in this sequence: a small ribosomal subunit + mRNA + large ribosomal unit + initiator tRNA (with anticodon AUG)
Elongation: A series of tRNA's delivers specific amino acids in sequence by codon-anticodon matching; a peptide bond joins each amino acid to the next sequence.
Termination: A stop codon is reached, and the polypeptide chain is released into the cytoplasm or enters the cytomembrane system for further processing.

Roles of Molecules Involved in Protein Synthesis:
1. DNA contains the code or "blueprint" for the protein to be synthesized.
2. mRNA carries a transcribed copy of the DNA code from the nucleus to the ribosomes in the cytoplasm.
3. tRNA carries a specific amino acid to the ribosome for assembly into polypeptides.
4. rRNA together with proteins forms ribosomes, which are the site of protein synthesis (translation).
5. Amino acids are the building blocks that are linked together by peptide (covalent) bonds to form polypeptides.
6. Various enzymes.

Examples:
Given the tRNA anticodon sequence: UCA GGU CCA AAA AGU
...determine
a.) the complementary mRNA codons:
AGU CCA GGU UUU UCA
b.) the polypeptides (amino acids):
serine, proline, alanine, phenylalanine, serine
c.) the original DNA code:
AGT CCA GGT TTT TCA

So What?
Protein synthesis is important because the proteins created during this process control the activities of the cells. It also forms the enzymes that catalyze the production of organic biomolecules that are essential for life. Therefore, many of the processes in the body would fail or work improperly without these proteins. The DNA in each cell contains the instructions on the formation of protein as well, which is why every cell in the body must have a copy of the DNA.

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Explanation:
DNA replication occurs in the nucleus of the cell, prior to cell division (mitosis or meiosis) and requires a supply of free nucleotides and specific enzymes. Each nucleotide strand serves as a template for the formation of a daughter strand.

Three Major Steps:
1. "Unwinding and Unzipping"
An enzyme (DNA helicase) causes the two strands that make up DNA to unzip, ultimately breaking the hydrogen bonds between complementary base pairs. Free bases are then exposed, which creates a replication fork.
2. Complementary Base Pairing
Free nucleotides (which are always present in the nucleus) move in place by the process of complementary base pairing (A=T, G=C). Enzymes (DNA polymerase) catalyze this process.
3. Joining of Adjacent Nucleotides
An enzyme (DNA polymerase) causes the phosphate of one nucleotide to join with the adjacent of the next nucleotide, creating phosphodiester bonds and forming new strands. As a result, two complete DNA molecules which are identical to each other and to the parent are made.

DNA is Antiparallel: Continuous vs. Discontinuous Replication:
In one of the two strands of the DNA double helix, the deoxyribose sugars are oriented so that the 5 prime carbon is pointing up while the 3 prime carbon is pointing down. This strand is described as the leading strand. In the other strand, the deoxyribose sugar is oriented so that the 3 prime carbon is pointing up while the 5 prime carbon is pointing down. This strand is described as the lagging strand. Since the two strands run in opposite directions, DNA is described as being antiparallel. DNA polymerase is directional and can only replicate the parental strand in the 3 prime to 5 prime direction. Also, DNA polymerase can attach to the 3 prime end of the parental strand and replicates the daughter strand continuously towards the replication fork. Furthermore, the 5 prime to 3 prime parental strand undergoes discontinuous replication and DNA polymerase works from the replication fork outward along the 5 prime to 3 prime parental strand, ultimately creating Okazaki fragments. Another enzyme called DNA ligase completes the sugar phosphate backbone of the daughter strand.

Examples:
Why is DNA replication called semi-conservative?
DNA replication is called semi-conservative because each of the two new DNA molecules contains one strand of the original DNA and one new strand.
What is the function of DNA helicase?
DNA helicase causes the two strands that make up DNA to unzip.

So What?
DNA replication is important because it allows for the creation of proteins, which are essential for bodily functions. It is also necessary that DNA is copied exactly because it ensures that each cell has a complete set of genes to pass to the next generation. Lastly, DNA replication is important because the genes that are present in parents are the same genes that are present in their children. Because of this, the identification of a family is possible.

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Explanation:
Proteins are made of amino acids linked together by peptide bonds (a type of covalent bond) to form chains. In fact, there are 20 different amino acids and they all consist of carbon, hydrogen, nitrogen, and oxygen atoms. Some amino acids contain other atoms (eg. sulphur) besides C, H, O, and N.

Peptide Bond Formation:
Peptide bonds are formed between amino acids as a result of dehydration synthesis reactions in which water is given off. Furthermore, when two amino acids are linked, a dipeptide is formed. And when many amino acids are joined by peptide bonds, the resulting chain is called a polypeptide. A protein can also be a single polypeptide chain, or composed of two or more amino acid chains linked together.

Levels of Protein Structure:
Primary Structure:
It is the linear sequence of amino acids joined by peptide bonds (determined by the sequence of bases in DNA).
Secondary Structure:
It is a regular, repeated 3-D shape of the amino acid chain and it is caused by hydrogen bonding between peptide bonds.
Tertiary Structure:
It is the final shape and is caused by various types of bonding (eg. covalent, ionic, and hydrogen) between R groups.
Quaternary Structure:
It is two or more separate polypeptide chains, sequence, and structure that join and work together. The combined structure is a fourth level of structure caused by hydrogen and ionic bonds between R groups.

Protein Denaturation:
Protein denaturation is when a protein loses its normal structure (secondary, tertiary, and quaternary), and therefore its shape, due to disruption of bonding between R groups. As a result, the protein can no longer function. In other words, the function of protein depends on its structure.
Causes of Denaturation:

extremes of heat

very high temperatures

addition of heavy metals (eg. mercury)

Examples:
What is the difference between the terms "polypeptide" and "protein"?
A polypeptide is a polymer of many amino acids linked by peptide bonds, whereas a protein is an organic macromolecule composed of one or several polypeptides.
What does the structure of an amino acid consist of?
The structure of an amino acid consists of an amino group, an R group (side chain), and an acid group (carboxyl).

So What?
Proteins are important because they are important building blocks of various parts of the human body. For instance, keratin (hair and nails), collagen (tendons and ligaments), and muscles are made up of proteins. Moreover, proteins also function as transportation (eg. hemoglobin transports oxygen and carbon dioxide in the blood), hormones (eg. insulin helps regulate sugar levels in the blood) and catalysts (enzymes) make possible chemical reactions at body temperature. Proteins also protect humans from getting sick because the antibodies produced by proteins protects the body against pathogens.

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Explanation:
There are two types of nucleic acids, which are deoxyribonucleic acid (DNA) and ribose (RNA). Nucleic acids also contain the elements carbon, hydrogen,  nitrogen, oxygen, and phosphorus. A nucleotide consists of a phosphorus phosphate group, a pentose sugar, and a nitrogenous base.

DNA:
DNA consists of two strands of nucleotide monomers linked together and twisted to form a double helix. The nitrogenous base in DNA could also be either adenine, thymine, guanine, or cytosine. The nitrogenous bases adenine and guanine are called purines and consist of two rings. Whereas cytosine and thymine are called pyrimidines and consist of one ring. To form a strand, the nucleotides are linked through their sugar and phosphate groups through the process of dehydration synthesis, ultimately creating phosphodiester bonds. Therefore, the resulting strand has a sugar-phosphate backbone in which the sugar and phosphate groups alternate. And the nitrogenous bases, which are attached to the deoxyribose sugar, project outward on one side of the strand.

RNA:
Like DNA, RNA is a polymer composed of monomers called nucleotides. Its nucleotides consist of three parts which include a phosphate group, a pentose sugar (ribose) and a nitrogenous based which could be either adenine, guanine, cytosine, or uracil. As in DNA, the parts of the RNA nucleotides are joined through the process of dehydration synthesis, then the RNA nucleotides are linked through their sugar and phosphate groups which creates phophodiester bonds. In contrast to DNA (which is double-stranded), RNA is also typically single-stranded.

Examples:
Name the monomer used to make nucleic acids.
The monomer used to make nucleic acids are called nucleotides.
Explain how the two strands of nucleotides are held together in DNA.
The hydrogen bonds between pairs of bases is how nucleotides are held together in DNA.

So What?
Nucleic acids are important because it determines the traits possessed by organisms by controlling the process of protein synthesis since nucleic acids control cell activities. Moreover, DNA contains the genetic code or information which determines the structure and function of those proteins. Lastly, RNA is involved in taking the genetic information from DNA and using it to link amino acids together in order to make the proteins.

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Explanation:

Lipids contain mostly carbon, hydrogen, and oxygen, but may also contain other elements such as nitrogen and phosphorus. Lipids are usually non polar, therefore relatively insoluble in water.

Neutral Fat (Triglycerides):

Structure:

Triglycerides are composed of one fat and three fatty acid chains which are combined by three dehydration synthesis reactions in which three water molecules are given off.

• saturated fatty acids (solid at room temperature):

These fats are saturated with hydrogen and have no double bonds between carbon atoms, and are typical of animal fats.

Example: butter, lard

• unsaturated fatty acids (liquid at room temperature):

Because of a deficiency of hydrogen atoms, these fats have double bonds between some of the carbon atoms, and are typical of plant fats.

Example: canola oil, olive oil

Function:

Triglycerides function as long term energy storage, insulates against the cold, and protects major organs.

Phospholipids:
Structure:
The structure of phospholipids are very similar to that of triglycerides except that the third fatty acid is replaced by a phosphate group, which in turn is often linked to a nitrogen-containing group. Due to the presence of the phosphate group, part of this molecule is polar (the "head" of the phospholipid), whereas the other two fatty acids are non-polar and are referred to as the "tail" of the phospholipid.
Function:
Phospholipids function as a major component of the cell membrane.

Steroids:
Structure:
The structure of steroids is very similar to cholesterol since they're derived from cholesterol. Steroids consist of three 6-carbon rings and one 5-carbon ring with one or more side chains.

Function:
Steroids function as sex hormones (Ex. progesterone, estrogen, testosterone), and cholesterol is often found in cell membranes which it helps to stabilize and strengthen. Also, the steroid aldosterone is a hormone which helps to control blood flow levels.

Example:
What is the key feature which helps to identify lipids?
The key feature that helps to identify lipids is that they are hydrophobic, meaning they are insoluble in water.
How does the structural difference between a triglyceride from an animal and a plant affect the physical properties of these neutral fats?
It affects the physical properties of these fats because unsaturated fats are liquid at room temperature, and the double bonds in unsaturated fatty acids will lower the melting point. As for saturated fatty acids, they are solid at room temperature.

So What?
Lipids are important because they play an extremely vital role in the human body. For instance, triglycerides act as a long term storage energy and 1 gram of fat stores more than two times the energy of 1 gram of carbohydrate. They also insulate against the cold and protects major organs. Moreover, phospholipids are the major component of the cell membrane. Lastly, steroids act as sex hormones, and cholesterol helps to stabilize and strengthen as well.

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Explanation:
Carbohydrates contain atoms of the elements carbon, hydrogen, and oxygen (CH2O). Carbohydrates can also be in the form of monosaccharides, disaccharides, and polysaccharides.

Monosaccharide:

Structure: Monosaccharides consist of a single chain of molecules.
Function: Monosaccharides, such as glucose, are the primary energy source for cells. Ribose and deoxyribose are the major components of DNA and RNA as well.

Disaccharide:

Structure: Disaccharides are formed when two monosaccharides are linked together through the process of dehydration synthesis during which a water molecule is given off.
Function: Disaccharides often serve as forms of energy storage.

Polysaccharide:

Structure: Polysaccharides are formed when many monosaccharides are linked together through many dehydration synthesis reactions in which many water molecules are released.
Starch: A fairly straight chain glucose polymer which may have a few side chains (joined by alpha 1/4 bonds).
Glycogen: A highly branched polymer of glucose (joined by alpha 1/4 bonds).
Cellulose: A straight chain polymer of glucose (joined by beta 1/4 bonds).

Examples:
Why are carbohydrates called carbohydrates?
Carbohydrates are called carbohydrates since the ratio of hydrogen to oxygen is 2:1 as it is in water.
What is the function of glycogen?
Glycogen is the major form in which the monosaccharide glucose is stored in animals.

So What?
Carbohydrates are important because they are sugars and starches– some of the building blocks of life. They are also used by the body as sources of energy, structural components of DNA and RNA, and it makes proteins. Moreover, carbohydrates are vital for the human diet. Most animals, including humans, have enzymes that can hydrolyze plant starch, making glucose available as a nutrient for cells. Foods such as potatoes, wheat, and corn are the major sources of starch in the human diet too. In other words, both animals and humans need carbohydrates to maintain energy.