Chapter 12: Pathways to Biomolecules ____________________ are molecules such as fats and oils, carbohydrates, proteins and nucleic acids that are found in all living things. They have an essential role in the supply of energy to the body, the growth and repair of organs and tissue, the ____________________ of muscles, the activity of nervous and hormonal systems and the elimination of waste. Many biomolcules are ____________________. Fats Humans can make their own fat ____________________. Though this is not usually necessary as fat is readily available in the food we eat. Fat is a name used to describe a large number of ____________________ compounds belonging to an even larger class of biological molecules called ____________________. Fats and oils are the best known types of lipids. Oil in food have very different ____________________ and properties from hydrocarbon oils. Compounds such as ____________________ and steroids (which include cholesterol) are also ____________________. Lipids are based mainly on carbon and hydrogen. They also contain small amounts of oxygen and sometimes some other elements. Most lipids are non-polar and ____________________ in water. Fats and oils have very similar chemical structures. They are simply distinguished on the basis of their physical states at normal temperatures: –Fats are ____________________ –Oils are ____________________ Most fats and oils are formed by a ____________________ reaction between a single molecule of ____________________ and three molecules of fatty acids. Fatty acids contain a carboxyl functional group which reacts with the hydroxyl groups in the glycerol. The –COO- groups in fat are ____________________ linkages. Three molecules of water are also produced in this reaction. Fats and oils formed from this process are called ____________________. Most fats have two or three different fatty acids attached to the glycerol molecule. Triglycerides are large, ____________________ -polar molecules and therefore are insoluble in aqueous. Draw an example of the production of a fat Fats are distinguishable on the basis of the ____________________ acids from which they are made: –____________________ fats are made from fatty acids, such as palmitic acid, that contain only single carbon-carbon bonds. Saturated fats are generally unreactive and occur as waxy solids at room temperature. –____________________ fats are made from fatty acids, such as oleic acid, that contain one carbon-carbon double bond. –____________________ fats are made from fatty acids, such as linoleic acid, that contain more than one carbon-carbon double bond. Polyunsaturated fats have lower melting temperatures than saturated fats and often occur at liquids, oils, are room temperature. They are more reactive than saturated fats. The different physical states of ____________________ and polyunsaturated fats are thought to arise because molecules of saturated fats can pack more ____________________ together, resulting in stronger ____________________ forces between the molecules. The arrangement of the carbon chain sections at the double bond sites of polyunsaturated fats do not permit close ____________________. Consequently saturated fats have higher ____________________ points than unsaturated fats. Chemical digestion of fat does not start until it reaches the small ____________________. There it is mixed with bile, from the gall bladder. Bile contains ____________________ that convert the fats into an ____________________ of smaller fat globules. This increases the surface area, meaning it is able to react more rapidly. Secretions from the pancreas and the walls of the small intestine contain enzymes that ____________________ the hydrolysis of fat into fatty acids and glycerol; reversing the condensation reaction from which fat was made. Enzymes in the small intestine operate best under ____________________ conditions. Once the fatty acids and glycerol have been absorbed into the body, they are reassembled into triglycerides via condensation reactions. (see page 180). Condensation and Polymerisation The monomers used to make polymers by a ____________________ polymerisation reaction have a pair of functional groups that are able to react together, producing a new functional groups that links ____________________ and also produces a small molecule such as water. ____________________ polymers such as nylon and polyester are formed in this way, are proteins, DNA, cellulose and starch. Carbohydrates The main structural component of all plants is a polymer called ____________________. Cellulose belongs to a class of compounds called ____________________. Green plants in the presence of sunlight, convert carbon dioxide and water into a number of substances including the carbohydrate ____________________. CHOs are a source of energy in our diets. CHOs are made from the element C, H and O and usually have the formula Cx(H2O)y, where x and y are whole numbers. CHOs range in size from small molecules, with Mr’s of between ____________________ and 200 to very large polymers with Mr greater than 1 ____________________. Monosaccharides Are the smallest CHOs. They are white crystalline solids that highly ____________________ in water. Most monosaccharides have a sweet taste. Monsaccharides together with another group of CHOs called ____________________ are often called sugars. The most abundant monosaccharide is ____________________. It has the molecular formula C6H12O6 and the atoms are arranged in a ring. ____________________ and Galactose have similar structures. All three of these molecules contain a number of ____________________ OH groups, enabling them to form hydrogen bonds with water. As a results monosaccharides are highly ____________________ in water. Draw the structure of glucose, fructose and galactose Glucose Is the key ____________________ source in most forms of life. It is also a major component of the larger CHOs. Glucose and its polymer, starch, are more rapidly ____________________ than other forms of food. Fructose & Galactose Are not as abundant as glucose. ____________________ is not found in nature as a free monosaccharide. It occurs frequently as a component of larger CHOs. ____________________ is found in many fruit juices and honey. Although fructose is a component of other large biological molecules, its main role in the body is an energy source. Disaccharides Is the carbohydrate formed when ____________________ monosaccharides undergo a ____________________ reaction. They too dissolve in water, taste sweet and are called sugars. Maltose is formed when two glucose molecules react, with the ____________________ of a water molecule. (a on next slide) Notice how the hydroxyl functional groups react to form the ____________________ and water. The two rings are joined via an oxygen atom. This linkage is called a ____________________ (or glycosidic) linkage. Give an example of the production of a disaccharide ____________________ and Sucrose are two other disaccharides. Lactose is made from a condensation reaction of glucose and ____________________. It is not as sweet as glucose. Lactose is synthesised in the mammary glands of mammals and is the main CHO in milk. Sucrose is formed from a condensation reaction of glucose and ____________________. It is widely used as a sweetener. It is found in the sap of trees and the juices of many fruits. Polysaccharides Are ____________________ carbohydrates made by linking monosaccharides into a chain. They are ____________________ of glucose molecules linked together in different ways by condensation reactions. They are generally ____________________ in water and have no taste. The three most important polysaccharides are: glycogen, starch and cellulose. Glycogen Is found in animals, where it acts as a glucose ____________________ molecule. As glucose can be ____________________ to produce energy more rapidly than fat, all glucose is polymerised to glycogen to be stored. When there is no more storage space for glycogen, the glucose is converted into fat. As energy is required, the glycogen is hydrolysed to yield glucose for ____________________. Starch The glucose storage molecule in ____________________; the plants equivalent of glycogen. The starch is stored and used at ____________________ to meet the plant’s ongoing energy requirements when the glucose production from ____________________ has ceased. Digestion During digestion, the ____________________ must be broken down to release the glucose monomers. The polymers are first ____________________. This hydrolysis is catalysed by enzymes; every 2nd glucose is hydrolysed to produce ____________________. Another enzyme catalyses the hydrolysis of maltose into glucose, which absorbed into the body. These can be regarded as the reverse of condensation reactions. Cellulose The main ____________________ material in plants. It has a Mr ranging from 50,000 to 2.5 million. Its chemical structure differs from starch and glycogen because of the ____________________ in the way the glucose monomers are joined. Draw the structures for starch and cellulose Proteins Proteins are found in every cell and are fundamental to cell ____________________ and operation. There are thousands of different types of proteins and each has its own purpose. Proteins are ____________________ built up from monomer molecules called ____________________ acids. Two of the simpler amino acids are glycine and alanine. Every amino acid has an amine group and a ____________________ group. They have the general formula of H2N-CHZ-COOH. The major difference between amino acid is the collection of atoms that make up the ____________________ chain, known as the Z group. Draw the general structure for an amino acid As a consequence of the polar amino and carboxyl functional groups; amino acids are ____________________ in water. In solution, the amino group can acts as a ____________________, and the carboxyl as an acid. As a result, the amino acid molecule in a solution at a particular pH will usually be in the form of +H3N-CHZ-COO-. This sort of molecule is called a ____________________ or dipolar ion. A proton has been lost from the acidic ____________________ group and the basic amino group has gained a ____________________. The pH at which an amino acid exists as a ____________________ depends on the structure of the Z group. The ____________________ acidic and basic nature of amino acids means that several different forms of an amino acid can be in equilibrium in a solution. The predominant form depends on the ____________________ of the solution. In acidic solutions, the +H3N-CHZCOOH form is most abundant, whereas H2N-CHZ-COO- form is most abundant in alkaline solutions. The ability of amino acids to react with both acids and bases means that they can act as ____________________. This means they minimise the effect that the addition of H+ or OH- ions to a solution would have on acidity. Protein Structure When a molecule containing a ____________________ combines with a molecule containing NH2, a condensation reaction occurs to form an amide functional group – CONH2-. This links the two molecules. ____________________ is also formed. Draw a reaction demonstrating an amide linkage Proteins are ____________________ formed by condensation reactions between amino acids. During these reactions the amino acids join and form long unbranched chains. The ____________________ group of one amino acid reacts with the ____________________ of another. A covalent bond is formed and a molecule of water is eliminated. Peptides Molecules made from amino acids are often called ____________________. When two amino acid molecules react together it is called a ____________________. When three molecules react and ____________________ is formed. A polymer made from amino acids is known as a ____________________. Polypeptides built up of more than 50 amino acids are usually called proteins. The group of atoms –CONH- that links the amino acids is an amide group, referred to as a ____________________ linkage in proteins. The role that any protein fulfils is dependent on its shape. This is regarded as being made up of a primary, secondary and tertiary structure. The order of the amino acids is known as the ____________________ structure. The entire shape of a protein is a consequence of the order in which the AAs are joined. Show Primary Structure Parts of the chain can attract each other creating 3D shapes. This coiling, folding or pleating of sections is described as the protein’s ____________________ structure. Show Secondary Structure The Z groups in the amino acid units of a protein influence the overall 3D shape of the molecule. The Z groups in some amino acids are relatively large and their size can cause distortions in the protein structure. Further, some of the side groups are capable of forming bonds with side groups elsewhere on the protein chain. As a consequence of such bonds, a variety of protein shapes exist. The overall 3D shape adopted by the protein is called its ____________________ structure. Show Tertiary Structure Enzymes Many chemical reactions occur more rapidly when a ____________________ is present. The biological catalysts that accelerate the rate of chemical reactions in living things are a type of protein called enzymes. Enzymes control the manufacture of complex substances as well as breaking down the ____________________ to provide energy. They are usually more efficient than inorganic catalysts, because they allow reactions to occur rapidly within the narrow band of temperature in which life can survive. Compared to ____________________ catalysts: –Enzymes produce much ____________________ reactions rates: they can increase the rate of a reaction by as much as 1010 times. –Enzymes operate under ____________________ conditions. –Enzymes are more ____________________: The catalytic activity of many enzymes is destroyed when they are heated strongly because their delicate structure breaks down. The enzyme is then described as being denatured. –Enzymes are very ____________________. The catalytic activity of an enzyme depends on its ____________________ structure. A slight change in its 3D shape can render an enzyme inoperative. The active site of an enzyme is usually a flexible hollow or cavity within the molecule. Some enzymes have small, non-protein parts called ____________________, such as vitamins or metal atoms associated with the active site. These cofactors are necessary for catalytic effect. The Lock and Key Process A reactant molecule, known as the ____________________, is manoeuvred into the active site. Here, at the surface of the enzyme the reaction takes place. The steps are as follows: 1.The ____________________ (substrate) enters the active site. 2.Bonds formed between the enzyme and substrate ____________________ bonds within the substrate, thus lowering the reaction’s activation energy. 3.The substrate breaks or ____________________ into new products and these products are released. Draw a diagram the demonstrates the lock and key process Typically reactions occur at a rate of 1000/second on an active site. During respiration the enzyme catalyses the decomposition of 600000 ____________________ acid molecules into carbon dioxide and water each second. In many cases the substrate and enzyme bind together because part of the substrate and active site are non polar and so dispersion forces are significant. In other cases, the substrate is held in place by the attraction between positive and ____________________ charges, attraction of a metal ion in the enzyme to a negative dipole in the substrate, or hydrogen bonding between enzyme and substrate. The selectivity of enzymes is one of their most important features. This selectivity arises because the shape and ____________________ groups in the active site of the enzyme allow it to bind only with certain substrates. (Thus the lock and key process). Some of the bonds that can occur between the substrate and enzyme include: –Ion-____________________ interactions –____________________ bonds –Ionic interactions –____________________ forces and dipole-dipole interactions may also be involved as an enzyme-substrate complex forms. Denaturation The bonds responsible for holding the protein chains in particular shapes are often weak, so slight changes can disrupt the attractions between parts of the chain. This causes the chain to ____________________ and render the protein ineffective. A change that destroys the biological ability of a protein is called ____________________. It may result due to an increased temperature, a change in pH or the addition of chemicals. ____________________ activity is dependent on temperature. As temperature ____________________, the rate of reaction catalysed by the enzyme increases because of increased collisions between enzyme and substrate, until an optimum temperature of 40°C is reached. As there is further temperature ____________________, the protein is denatured and the reaction rate rapidly ____________________. Enzymes operate effectively within a small ____________________ range. Not all enzymes have the same optimum pH. The ionisation of amino acids is depended on pH. The bonds that determine the ____________________ structure of the enzyme are altered as change in pH alter the ionisation of the amino acid ____________________ in the protein. Once a protein has been denatured, the unfolded chains tend to form randomly looped structures which come into close contact. The chains become ____________________ and bond with each other, often by disulfide bridges, so that large clumps of protein molecules are formed. This process is called ____________________. Draw a picture the demonstrates both denaturation and coagulation The body’s natural defences produce proteins called ____________________ in the fight against infection caused by bacteria or viruses. These antibodies are specific to a particular disease. The cells in diseased or damaged body organs may release specific proteins that are unique to that ____________________. A raised level of these marker ____________________ in a patient’s blood or tissue can be used to: –____________________ a disease at early or advanced stages of development. –____________________ the progress of the disease. –____________________ the effectiveness of treatment. –____________________ for the recurrence of the disease. A heart attack is caused when the blood supply to a part of the heart muscle is blocked by a clot in one of the cardiac arteries. The cardiac cells are starved of oxygen and nutrients and are consequently injured or die. The cells in the damaged part of the heart muscle release various cardiac ____________________ into the bloodstream. Blood levels of these enzymes increase within a few hours after a heart attack and drop back to normal after several days. Cancer is an uncontrolled growth of cells. It is initially diagnosed by digital examination and by measuring the level of a protein in the blood. Normally a small amount of this protein is present in the blood. Abnormal cancerous or non-cancerous cell growths block the ducts in the prostate, forcing more of this protein into the bloodstream. The concentration of this protein in the blood is used as a marker for possible prostate cancer.