What kind of macromolecules is made from amino acids

To function properly, cell membranes have to be in a fluid state. How do you expect the fatty acid content saturated versus unsaturated of bacteria living in high-temperature environments might compare with that of bacteria living in more moderate temperatures?

Describe the structure of a typical phospholipid. Are these molecules polar or nonpolar? Glyceraldehyde can exist in two isomeric forms that are mirror images of each other which are shown below.

The absolute configuration is defined by the molecule on the far left as the D-glyceraldehyde. Chemists have used this configuration of D-glyceraldehyde to determine the optical isomer families of the rest of the carbohydrates.

All naturally occurring monosaccharides belong to the D optical family. It is remarkable that the chemistry and enzymes of all living things can tell the difference between the geometry of one optical isomer over the other.

Monosaccharides are assigned to the D-family according to the projection of the -OH group to the right on the chiral carbon that is the farthest from the carbonyl aldehyde group.

This is on carbon 5 if the carbonyl carbon is 1. Note: For whatever reason, the ball and stick model does not completely match the projections of the -OH groups on carbons 2 and 4.

It is in the way that the flat Fischer model has been defined. How many chiral carbons can you find? List them. If necessary Review Chiral Compounds to find the definitions. Then check the answer from the drop down menu. Examine the structures of glucose and galactose carefully. Which -OH group determines that they both are the D isomer? Isomers have different arrangements of atoms. Which carbon bonding to -OH and -H is different in glucose vs.

This single difference makes glucose and galactose isomers. The chemistry of carbohydrates most closely resembles that of alcohol, aldehyde, and ketone functional groups.

The chemistry of carbohydrates is complicated by the fact that there is a functional group alcohol on almost every carbon. In addition, the carbohydrate may exist in either a straight chain or a ring structure. Ring structures incorporate two additional functional groups: the hemiacetal and acetal. A major part of the carbon cycle occurs as carbon dioxide is converted to carbohydrates through photosynthesis.

Carbohydrates are utilized by animals and humans in metabolism to produce energy and other compounds. Photosynthesis is a complex series of reactions carried out by algae, phytoplankton, and the leaves in plants, which utilize the energy from the sun. The simplified version of this chemical reaction is to utilize carbon dioxide molecules from the air and water molecules and the energy from the sun to produce a simple sugar such as glucose and oxygen molecules as a by product.

Metabolism occurs in animals and humans after the ingestion of organic plant or animal foods. In the cells a series of complex reactions occurs with oxygen to convert for example glucose sugar into the products of carbon dioxide and water and ENERGY. Combustion occurs when any organic material is reacted burned in the presence of oxygen to give off the products of carbon dioxide and water and ENERGY. The organic material can be any fossil fuel such as natural gas methane , oil, or coal.

Other organic materials that combust are wood, paper, plastics, and cloth. The whole purpose of both processes is to convert chemical energy into other forms of energy such as heat. See Fischer projection. Step 6 : Add the ligands on C-2 through C-5 in 4.

The ligands pointing up in 3 are pointing up in 4; those pointing down in 3 are pointing down in 4. Step 7 : Remove the hydrogen atom and the oxygen atom on C-1 and the hydrogen atom in the hydroxy group on C-5 in 5 and connect the two atoms by a single bond.

Step 9: Attach a hydrogen atom to the bond pointing up and a hydroxy group to the bond pointing down on C-1 in 7. The most common fatty acids are listed. Note that there are two groups of fatty acids—saturated and unsaturated. Recall that the term unsaturated refers to the presence of one or more double bonds between carbons as in alkenes.

A saturated fatty acid has all bonding positions between carbons occupied by hydrogens. The melting points for the saturated fatty acids follow the boiling point principle observed previously. Melting point principle: as the molecular weight increases, the melting point increases. This observed in the series lauric C12 , palmitic C16 , stearic C Room temperature is 25 o C, Lauric acid which melts at 44 o is still a solid, while arachidonic acid has long since melted at o , so it is a liquid at room temperature.

Note that as a group, the unsaturated fatty acids have lower melting points than the saturated fatty acids. The reason for this phenomenon can be found by a careful consideration of molecular geometries. The tetrahedral bond angles on carbon results in a molecular geometry for saturated fatty acids that is relatively linear although with zigzags. See graphic on the left.

As a result, close intermolecular interactions result in relatively high melting points. The geometry of the double bond is almost always a cis configuration in natural fatty acids. The intermolecular interactions are much weaker than saturated molecules. As a result, the melting points are much lower for unsaturated fatty acids.

Unsaturated fatty acids may be converted to saturated fatty acids by the relatively simple hydrogenation reaction. Recall that the addition of hydrogen to an alkene unsaturated results in an alkane saturated. A simple hydrogenation reaction is:. This simply means that there are several double bonds present. Vegetable oils may be converted from liquids to solids by the hydrogenation reaction.

Vegetable oils which have been partially hydrogenated, are now partially saturated so the melting point increases to the point where a solid is present at room temperature. The degree of hydrogenation of unsaturated oils controls the final consistency of the product.

What has happened to the healthfulness of the product which has been converted from unsaturated to saturated fats? A major health concern during the hydrogenation process is the production of trans fats. Trans fats are the result of a side reaction with the catalyst of the hydrogenation process. This is the result of an unsaturated fat which is normally found as a cis isomer converts to a trans isomer of the unsaturated fat.

Isomers are molecules that have the same molecular formula but are bonded together differently. Focusing on the sp 2 double bonded carbons, a cis isomer has the hydrogens on the same side. Due to the added energy from the hydrogenation process, the activation energy is reached to convert the cis isomers of the unsaturated fat to a trans isomer of the unsaturated fat.

The effect is putting one of the hydrogens on the opposite side of one of the carbons. This results in a trans configuration of the double bonded carbons.

The human body does not recognize trans fats. Most of the trans fatty acids although chemically still unsaturated produced by the partial hydrogenation process are now classified in the same category as saturated fats. Trans fat are found in margarine, baked goods such as doughnuts and Danish pastry, deep-fried foods like fried chicken and French-fried potatoes, snack chips, imitation cheese, and confectionery fats.

Prostaglandins are unsaturated carboxylic acids, consisting of of a 20 carbon skeleton that also contains a five member ring. They are biochemically synthesized from the fatty acid, arachidonic acid.

See the graphic on the left. The unique shape of the arachidonic acid caused by a series of cis double bonds helps to put it into position to make the five member ring. See the prostaglandin in the next panel.

Prostaglandins are unsaturated carboxylic acids, consisting of of a 20 carbon skeleton that also contains a five member ring and are based upon the fatty acid, arachidonic acid.

There are a variety of structures one, two, or three double bonds. On the five member ring there may also be double bonds, a ketone, or alcohol groups. A typical structure is on the left graphic. When you see that prostaglandins induce inflammation, pain, and fever, what comes to mind but aspirin. Aspirin blocks an enzyme called cyclooxygenase, COX-1 and COX-2, which is involved with the ring closure and addition of oxygen to arachidonic acid converting to prostaglandins.

The acetyl group on aspirin is hydrolzed and then bonded to the alcohol group of serine as an ester. This has the effect of blocking the channel in the enzyme and arachidonic can not enter the active site of the enzyme.

By inhibiting or blocking this enzyme, the synthesis of prostaglandins is blocked, which in turn relives some of the effects of pain and fever. Aspirin is also thought to inhibit the prostaglandin synthesis involved with unwanted blood clotting in coronary heart disease. At the same time an injury while taking aspirin may cause more extensive bleeding. Since glycerol has three alcohol functional groups, three fatty acids must react to make three ester functional groups. The three fatty acids may or may not be identical.

In fact, three different fatty acids may be present. The synthesis of a triglyceride is another application of the ester synthesis reaction.

To write the structure of the triglyceride you must know the structure of glycerol and be given or look up the structure of the fatty acid in the table. Since glycerol, IUPAC name is 1,2,3-propantriol , has three alcohol functional groups, three fatty acids must react to make three ester functional groups. To write the structure of the triglyceride you must know the structure of glycerol and be given or look up the structure of the fatty acid in the table — find lauric acid.

Glycerol The simplified reaction reveals the process of breaking some bonds and forming the ester and the by product, water. Refer to the graphic on the left for the synthesis of trilauroylglycerol. First, the -OH red bond on the acid is broken and the -H red bond on the alcohol is also broken. Both join to make HOH, a water molecule. Secondly, the oxygen of the alcohol forms a bond green to the acid at the carbon with the double bond oxygen.

This forms the ester functional group. This process is carried out three times to make three ester groups and three water molecules. As you can see from the graphic on the left, the actual molecular model of the triglyceride does not look at all like the line drawing. The reason for this difference lies in the concepts of molecular geometry.

Again look up the formula of stearic acid and use the structure of glycerol. The third oxygen on glycerol is bonded to phosphoric acid through a phosphate ester bond oxygen-phosphorus double bond oxygen. In addition, there is usually a complex amino alcohol also attached to the phosphate through a second phosphate ester bond. The complex amino alcohols include choline, ethanolamine, and the amino acid-serine.

The long hydrocarbon chains of the fatty acids are of course non-polar. The phosphate group has a negatively charged oxygen and a positively charged nitrogen to make this group ionic. In addition there are other oxygen of the ester groups, which make on whole end of the molecule strongly ionic and polar. Phospholipids are major components in the lipid bilayers of cell membranes.

There are two common phospholipids:. Lecithin is probably the most common phospholipid. It is found in egg yolks, wheat germ, and soybeans. Lecithin is extracted from soy beans for use as an emulsifying agent in foods. Lecithin is an emulsifier because it has both polar and non-polar properties, which enable it to cause the mixing of other fats and oils with water components. See more discussion on this property in soaps. Lecithin is also a major component in the lipid bilayers of cell membranes.

Lecithin contains the ammonium salt of choline joined to the phosphate by an ester linkage. The nitrogen has a positive charge, just as in the ammonium ion. In choline, the nitrogen has the positive charge and has four methyl groups attached. Cephalins are phosphoglycerides that contain ehtanolamine or the amino acid serine attached to the phosphate group through phosphate ester bonds. A variety of fatty acids make up the rest of the molecule.

Cephalins are found in most cell membranes, particularly in brain tissues. They also iimportant in the blood clotting process as they are found in blood platelets.

Note: The MEP coloration of the electrostatic potential does not show a strong red color for the phosphate-amino alcohol portion of the molecule as it should to show the strong polar property of that group.

Steroids include such well known compounds as cholesterol, sex hormones, birth control pills, cortisone, and anabolic steroids. The best known and most abundant steroid in the body is cholesterol.

Cholesterol is formed in brain tissue, nerve tissue, and the blood stream. It is the major compound found in gallstones and bile salts. Cholesterol also contributes to the formation of deposits on the inner walls of blood vessels. These deposits harden and obstruct the flow of blood. This condition, known as atherosclerosis, results in various heart diseases, strokes, and high blood pressure.

Much research is currently underway to determine if a correlation exists between cholesterol levels in the blood and diet. Not only does cholesterol come from the diet, but cholesterol is synthesized in the body from carbohydrates and proteins as well as fat. Therefore, the elimination of cholesterol rich foods from the diet does not necessarily lower blood cholesterol levels.

Some studies have found that if certain unsaturated fats and oils are substituted for saturated fats, the blood cholesterol level decreases. The research is incomplete on this problem. Sex hormones are also steroids. The primary male hormone, testosterone, is responsible for the development of secondary sex characteristics. Two female sex hormones, progesterone and estrogen or estradiol control the ovulation cycle.

Notice that the male and female hormones have only slight differences in structures, but yet have very different physiological effects. Testosterone promotes the normal development of male genital organs ans is synthesized from cholesterol in the testes.

It also promotes secondary male sexual characteristics such as deep voice, facial and body hair. Estrogen, along with progesterone regulates changes occurring in the uterus and ovaries known as the menstrual cycle.

For more details see Birth Control. Estrogen is synthesized from testosterone by making the first ring aromatic which results in mole double bonds, the loss of a methyl group and formation of an alcohol group. The most important mineralocrticoid is aldosterone , which regulates the reabsorption of sodium and chloride ions in the kidney tubules and increases the loss of potassium ions.

Aldosterone is secreted when blood sodium ion levels are too low to cause the kidney to retain sodium ions. If sodium levels are elevated, aldosterone is not secreted, so that some sodium will be lost in the urine. Aldosterone also controls swelling in the tissues. Cortisol, the most important glucocortinoid, has the function of increasing glucose and glycogen concentrations in the body. These reactions are completed in the liver by taking fatty acids from lipid storage cells and amino acids from body proteins to make glucose and glycogen.

In addition, cortisol and its ketone derivative, cortisone , have the ability to inflammatory effects. Cortisone or similar synthetic derivatives such as prednisolone are used to treat inflammatory diseases, rheumatoid arthritis, and bronchial asthma.

There are many side effects with the use of cortisone drugs, so there use must be monitored carefully. The large molecules necessary for life that are built from smaller organic molecules are called biological macromolecules. There are four major classes of biological macromolecules carbohydrates, lipids, proteins, and nucleic acids , and each is an important component of the cell and performs a wide array of functions.

Biological macromolecules are organic, meaning that they contain carbon. In addition, they may contain hydrogen, oxygen, nitrogen, phosphorus, sulfur, and additional minor elements. It is the bonding properties of carbon atoms that are responsible for its important role. Carbon contains four electrons in its outer shell. Therefore, it can form four covalent bonds with other atoms or molecules. The simplest organic carbon molecule is methane CH 4 , in which four hydrogen atoms bind to a carbon atom.

However, structures that are more complex are made using carbon. Any of the hydrogen atoms can be replaced with another carbon atom covalently bonded to the first carbon atom. In this way, long and branching chains of carbon compounds can be made Figure 2. The carbon atoms may bond with atoms of other elements, such as nitrogen, oxygen, and phosphorus Figure 2.

The molecules may also form rings, which themselves can link with other rings Figure 2. This diversity of molecular forms accounts for the diversity of functions of the biological macromolecules and is based to a large degree on the ability of carbon to form multiple bonds with itself and other atoms.

Carbohydrates are macromolecules with which most consumers are somewhat familiar. Carbohydrates are, in fact, an essential part of our diet; grains, fruits, and vegetables are all natural sources of carbohydrates.

Carbohydrates provide energy to the body, particularly through glucose, a simple sugar. Carbohydrates also have other important functions in humans, animals, and plants. Carbohydrates can be represented by the formula CH 2 O n , where n is the number of carbon atoms in the molecule.

In other words, the ratio of carbon to hydrogen to oxygen is in carbohydrate molecules. Carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides.

In monosaccharides, the number of carbon atoms usually ranges from three to six. Most monosaccharide names end with the suffix -ose. Depending on the number of carbon atoms in the sugar, they may be known as trioses three carbon atoms , pentoses five carbon atoms , and hexoses six carbon atoms. Monosaccharides may exist as a linear chain or as ring-shaped molecules; in aqueous solutions, they are usually found in the ring form. The chemical formula for glucose is C 6 H 12 O 6. In most living species, glucose is an important source of energy.

During cellular respiration, energy is released from glucose, and that energy is used to help make adenosine triphosphate ATP. Plants synthesize glucose using carbon dioxide and water by the process of photosynthesis, and the glucose, in turn, is used for the energy requirements of the plant. The excess synthesized glucose is often stored as starch that is broken down by other organisms that feed on plants.

Galactose part of lactose, or milk sugar and fructose found in fruit are other common monosaccharides. Although glucose, galactose, and fructose all have the same chemical formula C 6 H 12 O 6 , they differ structurally and chemically and are known as isomers because of differing arrangements of atoms in the carbon chain. During this process, the hydroxyl group —OH of one monosaccharide combines with a hydrogen atom of another monosaccharide, releasing a molecule of water H 2 O and forming a covalent bond between atoms in the two sugar molecules.

Common disaccharides include lactose, maltose, and sucrose. Lactose is a disaccharide consisting of the monomers glucose and galactose.

It is found naturally in milk. Maltose, or malt sugar, is a disaccharide formed from a dehydration reaction between two glucose molecules. The most common disaccharide is sucrose, or table sugar, which is composed of the monomers glucose and fructose. The chain may be branched or unbranched, and it may contain different types of monosaccharides. Polysaccharides may be very large molecules. Starch, glycogen, cellulose, and chitin are examples of polysaccharides. Starch is the stored form of sugars in plants and is made up of amylose and amylopectin both polymers of glucose.

Plants are able to synthesize glucose, and the excess glucose is stored as starch in different plant parts, including roots and seeds. The starch that is consumed by animals is broken down into smaller molecules, such as glucose. The cells can then absorb the glucose. Glycogen is the storage form of glucose in humans and other vertebrates, and is made up of monomers of glucose.

Glycogen is the animal equivalent of starch and is a highly branched molecule usually stored in liver and muscle cells. Whenever glucose levels decrease, glycogen is broken down to release glucose. Cellulose is one of the most abundant natural biopolymers. The cell walls of plants are mostly made of cellulose, which provides structural support to the cell. Wood and paper are mostly cellulosic in nature.

Cellulose is made up of glucose monomers that are linked by bonds between particular carbon atoms in the glucose molecule. Every other glucose monomer in cellulose is flipped over and packed tightly as extended long chains.

This gives cellulose its rigidity and high tensile strength—which is so important to plant cells. Cellulose passing through our digestive system is called dietary fiber. While the glucose-glucose bonds in cellulose cannot be broken down by human digestive enzymes, herbivores such as cows, buffalos, and horses are able to digest grass that is rich in cellulose and use it as a food source.

In these animals, certain species of bacteria reside in the rumen part of the digestive system of herbivores and secrete the enzyme cellulase.

The appendix also contains bacteria that break down cellulose, giving it an important role in the digestive systems of ruminants. Cellulases can break down cellulose into glucose monomers that can be used as an energy source by the animal. Carbohydrates serve other functions in different animals. Arthropods, such as insects, spiders, and crabs, have an outer skeleton, called the exoskeleton, which protects their internal body parts. This exoskeleton is made of the biological macromolecule chitin , which is a nitrogenous carbohydrate.

It is made of repeating units of a modified sugar containing nitrogen. The starch that is consumed by animals is broken down into smaller molecules, such as glucose. The cells can then absorb the glucose. Glycogen is the storage form of glucose in humans and other vertebrates, and is made up of monomers of glucose. Glycogen is the animal equivalent of starch and is a highly branched molecule usually stored in liver and muscle cells. Whenever glucose levels decrease, glycogen is broken down to release glucose.

Cellulose is one of the most abundant natural biopolymers. The cell walls of plants are mostly made of cellulose, which provides structural support to the cell. Wood and paper are mostly cellulosic in nature. Cellulose is made up of glucose monomers that are linked by bonds between particular carbon atoms in the glucose molecule. Every other glucose monomer in cellulose is flipped over and packed tightly as extended long chains.

This gives cellulose its rigidity and high tensile strength—which is so important to plant cells. Cellulose passing through our digestive system is called dietary fiber. While the glucose-glucose bonds in cellulose cannot be broken down by human digestive enzymes, herbivores such as cows, buffalos, and horses are able to digest grass that is rich in cellulose and use it as a food source.

In these animals, certain species of bacteria reside in the rumen part of the digestive system of herbivores and secrete the enzyme cellulase. The appendix also contains bacteria that break down cellulose, giving it an important role in the digestive systems of ruminants. Cellulases can break down cellulose into glucose monomers that can be used as an energy source by the animal. Carbohydrates serve other functions in different animals. Arthropods, such as insects, spiders, and crabs, have an outer skeleton, called the exoskeleton, which protects their internal body parts.

This exoskeleton is made of the biological macromolecule chitin , which is a nitrogenous carbohydrate. It is made of repeating units of a modified sugar containing nitrogen. Thus, through differences in molecular structure, carbohydrates are able to serve the very different functions of energy storage starch and glycogen and structural support and protection cellulose and chitin. Registered Dietitian: Obesity is a worldwide health concern, and many diseases, such as diabetes and heart disease, are becoming more prevalent because of obesity.

This is one of the reasons why registered dietitians are increasingly sought after for advice. Registered dietitians help plan food and nutrition programs for individuals in various settings. They often work with patients in health-care facilities, designing nutrition plans to prevent and treat diseases. For example, dietitians may teach a patient with diabetes how to manage blood-sugar levels by eating the correct types and amounts of carbohydrates.

Dietitians may also work in nursing homes, schools, and private practices. In addition, registered dietitians must complete a supervised internship program and pass a national exam. Those who pursue careers in dietetics take courses in nutrition, chemistry, biochemistry, biology, microbiology, and human physiology. Dietitians must become experts in the chemistry and functions of food proteins, carbohydrates, and fats.

The underground storage bulb of the camas flower shown below has been an important food source for many of the Indigenous peoples of Vancouver Island and throughout the western area of North America.

Camas bulbs are still eaten as a traditional food source and the preparation of the camas bulbs relates to this text section about carbohydrates. Most often plants create starch as the stored form of carbohydrate. Some plants, like camas create inulin. Inulin is used as dietary fibre however, it is not readily digested by humans. If you were to bite into a raw camas bulb it would taste bitter and has a gummy texture. The method used by Indigenous peoples to make camas both digestible and tasty is to bake the bulbs slowly for a long period in an underground firepit covered with specific leaves and soil.

The heat acts like our pancreatic amylase enzyme and breaks down the long chains of inulin into digestible mono and di-saccharides. Properly baked, the camas bulbs taste like a combination of baked pear and cooked fig. It is important to note that while the blue camas is a food source, it should not be confused with the white death camas, which is particularly toxic and deadly. The flowers look different, but the bulbs look very similar.

Lipids include a diverse group of compounds that are united by a common feature. This is because they are hydrocarbons that include only nonpolar carbon-carbon or carbon-hydrogen bonds. Lipids perform many different functions in a cell. Cells store energy for long-term use in the form of lipids called fats.

Lipids also provide insulation from the environment for plants and animals. For example, they help keep aquatic birds and mammals dry because of their water-repelling nature. Lipids are also the building blocks of many hormones and are an important constituent of the plasma membrane.

Lipids include fats, oils, waxes, phospholipids, and steroids. A fat molecule, such as a triglyceride, consists of two main components—glycerol and fatty acids.

Glycerol is an organic compound with three carbon atoms, five hydrogen atoms, and three hydroxyl —OH groups. In a fat molecule, a fatty acid is attached to each of the three oxygen atoms in the —OH groups of the glycerol molecule with a covalent bond. During this covalent bond formation, three water molecules are released.

The three fatty acids in the fat may be similar or dissimilar. These fats are also called triglycerides because they have three fatty acids. Some fatty acids have common names that specify their origin. For example, palmitic acid, a saturated fatty acid, is derived from the palm tree.

Arachidic acid is derived from Arachis hypogaea , the scientific name for peanuts. Fatty acids may be saturated or unsaturated. In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is saturated. Saturated fatty acids are saturated with hydrogen; in other words, the number of hydrogen atoms attached to the carbon skeleton is maximized.

When the hydrocarbon chain contains a double bond, the fatty acid is an unsaturated fatty acid. Most unsaturated fats are liquid at room temperature and are called oils. If there is one double bond in the molecule, then it is known as a monounsaturated fat e. Saturated fats tend to get packed tightly and are solid at room temperature.

Animal fats with stearic acid and palmitic acid contained in meat, and the fat with butyric acid contained in butter, are examples of saturated fats.

Mammals store fats in specialized cells called adipocytes, where globules of fat occupy most of the cell. In plants, fat or oil is stored in seeds and is used as a source of energy during embryonic development. Unsaturated fats or oils are usually of plant origin and contain unsaturated fatty acids. Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats.

Unsaturated fats help to improve blood cholesterol levels, whereas saturated fats contribute to plaque formation in the arteries, which increases the risk of a heart attack. In the food industry, oils are artificially hydrogenated to make them semi-solid, leading to less spoilage and increased shelf life.

Simply speaking, hydrogen gas is bubbled through oils to solidify them. During this hydrogenation process, double bonds of the cis -conformation in the hydrocarbon chain may be converted to double bonds in the trans -conformation. This forms a trans -fat from a cis -fat. The orientation of the double bonds affects the chemical properties of the fat. Margarine, some types of peanut butter, and shortening are examples of artificially hydrogenated trans -fats.

Many fast food restaurants have recently eliminated the use of trans -fats, and U. Essential fatty acids are fatty acids that are required but not synthesized by the human body. Consequently, they must be supplemented through the diet.

Omega-3 fatty acids fall into this category and are one of only two known essential fatty acids for humans the other being omega-6 fatty acids. They are a type of polyunsaturated fat and are called omega-3 fatty acids because the third carbon from the end of the fatty acid participates in a double bond. Salmon, trout, and tuna are good sources of omega-3 fatty acids. Omega-3 fatty acids are important in brain function and normal growth and development.

They may also prevent heart disease and reduce the risk of cancer. Like carbohydrates, fats have received a lot of bad publicity. However, fats do have important functions. Fats serve as long-term energy storage. Thus, glycosylations are important in immune response and general cell-to-cell communication. After nucleic acids, proteins are the most important macromolecules.

Structurally, proteins are the most complex macromolecules. A protein is a linear molecule comprised of amino acids. Twenty different amino acids are found in proteins.

A single protein molecule may be comprised of hundreds of amino acids. The amino acid chain can remain in its primary linear structure, but often it folds up and in on itself to form a shape. This secondary structure forms from localized interactions hydrogen bonding of amino acid side chains. These include alpha helix and beta sheet structures. The alpha helix is dominant in hemoglobin, which facilitates transport of oxygen in blood. Secondary structures are integrated along with twists and kinks into a three-dimensional protein.

This functional form is called the tertiary structure of the protein. An additional level of organization results when several separate proteins combine to form a protein complex—called quaternary structure. Proteins perform numerous essential functions within the cell. Many proteins serve as enzymes, which control the rate of chemical reactions, and hence the responsiveness of cells to external stimuli. An enzyme can fast-forward a reaction that would take millions of years under normal conditions and make it happen in just a few milliseconds.

Enzymes are important in DNA replication, transcription and repair. Digestive processes are also largely facilitated by enzymes, which break down molecules that would otherwise be too large to be absorbed by the intestines.

Enzymatic proteins also play a role in muscle contractions. Other proteins are important in cell signaling and cell recognition. Receptor proteins recognize substances as foreign and initiate an immune response. Through cell signaling, proteins mediate cell growth and differentiation during development. Several important proteins provide mechanical support for the cell, scaffolding that helps the cell maintain its shape.

For protein production in cells the body needs amino acids, which we ingest. It seems a bit inefficient, but we eat proteins, break them down into amino acids, distribute the amino acids inside the body and then build up new proteins. Our cells can synthesize some amino acids from similar ones, but essential amino acids must be obtained from the diet, since they cannot be synthesized. Deficiencies of protein in the diet result in malnutrition diseases such as kwashiorkor, which is common in developing countries.

In cases of kwashiorkor, protein deficiency causes edema swelling which leads to a distended abdomen. Proteins are eventually metabolized into ammonia and urea, which are excreted by the kidneys. Kidney disease can cause these waste products to accumulate in the body, causing someone to become very ill, ultimately leading to death.

A low protein diet can help those whose kidneys have a low level of function. Unlike nucleic acids, which must remain unchanged in the body for the life of the organism, proteins are meant to be transient—they are produced, do their functions and then are recycled.

Proteins are also readily denatured unfolding of the secondary and tertiary structures by extremes of heat or pH. When you boil an egg, the yolk and white stiffen and change color.