Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 19 Enzymes and Vitamins 19.1 19.2 19.3 19.4 Biological Catalysts Names and Classification of Enzymes Enzymes as Catalysts Factors Affecting Enzyme Activity Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 1 19.1 Catalysis by Enzymes Enzymes are proteins that: Increase the rate of reaction by lowering the energy of activation. Catalyze nearly all the chemical reactions taking place in the cells of the body. Have unique threedimensional shapes that fit the shapes of reactants. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 2 Enzymes are specific with respect to stereochemistry – catalyze reaction of only one of the pair of enantiomers. For example, the enzyme lactate dehydrogenase catalyzes the removal of hydrogen from L-lactate but not from Dlactate. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 3 The specificity of an enzyme for one of two enantiomers is a matter of fit. One enantiomer fits better into the active site of the enzyme than the other enantiomer. Enzyme catalyzes reaction of the enantiomer that fits better into the active site of the enzyme. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 4 Names of Enzymes The name of an enzyme: Usually ends in –ase. Identifies the reacting substance. For example, sucrase catalyzes the reaction of sucrose. Describes the function of the enzyme. For example, oxidases catalyze oxidation. Could be a common name, particularly for the digestion enzymes such as pepsin and trypsin. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 5 19.2 Enzyme Cofactors Please see section 19.8 of these slides. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 6 19.3 Enzyme Classification Enzymes are classified according to the reaction they catalyze. Class Reactions catalyzed Oxidoreductases Oxidation-reduction Transferases Transfer groups of atoms Hydrolases Hydrolysis Lyases Add atoms/remove atoms to/from a double bond Isomerases Rearrange atoms Ligases Use ATP to combine molecules Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 7 Classification of Enzymes: Oxidoreductases and Transferases Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 8 Classification: Hydrolases and Lyases Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 9 Classification: Isomerases and Ligases Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 10 Learning Check Match the type of reaction with an enzyme: 1) aminase 2) dehydrogenase 3) isomerase 4) synthetase A. B. C. D. Converts a cis-fatty acid to a trans-fatty acid. Removes 2 H atoms to form double bond. Combine two molecules using ATP. Adds NH3. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 11 Solution Match the type of reaction with an enzyme: 1) aminase 2) dehydrogenase 3) isomerase 4) synthetase A. 3 Converts a cis-fatty acid to a trans-fatty acid. B. 2 Removes 2 H atoms to form double bond. C. 4 Combine two molecules using ATP. D. 1 Adds NH3. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 12 19.4 How Enzymes Work The active site: Is a region within an enzyme that fits the shape of molecules called substrates. Contains amino acid R groups that align and bind the substrate. Releases products when the reaction is complete. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 13 Hydrolysis of a peptide bond by Chymotripsin Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 14 Enzyme Specificity Enzymes may recognize and catalyze: A single substrate. A group of similar substrates. A particular type of bond. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 15 Lock-and-Key Model In the lock-and-key model of enzyme action: The active site has a rigid shape. Only substrates with the matching shape can fit. The substrate is a key that fits the lock of the active site. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 16 Induced-fit Model In the induced-fit model of enzyme action: The active site is flexible, not rigid. The shapes of the enzyme, active site, and substrate adjust to maximize the fit, which improves catalysis. There is a greater range of substrate specificity. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 17 Enzyme Catalyzed Reaction The proper fit of a substrate (S) in an active site forms an enzyme-substrate (ES) complex. E+S ES Within the ES complex, the reaction occurs to convert substrate to product (P). ES E+P The products, which are no longer attracted to the active site, are released. Overall, substrate is converted to product. E+S ES E+P Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 18 Example of An Enzyme Catalyzed Reaction Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 19 Learning Check A. The active site is: 1) The enzyme shape. 2) A section of the enzyme. 3) The substrate. B. In the induced-fit model, the shape of the enzyme when substrate binds: 1) Stays the same. 2) Adapts to the shape of the substrate. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 20 Solution A. The active site is: 2) A section of the enzyme. B. In the induced-fit model, the shape of the enzyme when substrate binds: 2) Adapts to the shape of the substrate. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 21 Diagnostic Enzymes The levels of diagnostic enzymes determine the amount of damage in tissues. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 22 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 23 19.6 Temperature and Enzyme Action Enzymes: Are most active at an optimum temperature (usually 37°C in humans). Show little activity at low temperatures. Lose activity at high temperatures as denaturation occurs. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 24 pH and Enzyme Action Enzymes: Are most active at optimum pH. Contain R groups of amino acids with proper charges at optimum pH. Lose activity in low or high pH as tertiary structure is disrupted. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 25 Optimum pH Values Most enzymes of the body have an optimum pH of about 7.4. In certain organs, enzymes operate at lower and higher optimum pH values. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 26 Optimum pH Values Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 27 Enzyme Concentration The rate of reaction increases as enzyme concentration increases (at constant substrate concentration). At higher enzyme concentrations, more substrate binds with enzyme. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 28 Substrate Concentration The rate of reaction increases as substrate concentration increases (at constant enzyme concentration). Maximum activity occurs when the enzyme is saturated. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 29 Learning Check Sucrase has an optimum temperature of 37°C and an optimum pH of 6.2. Determine the effect of the following on its rate of reaction. 1) no change 2) increase 3) decrease A. Increasing the concentration of sucrose B. Changing the pH to 4 C. Running the reaction at 70°C Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 30 Solution Sucrase has an optimum temperature of 37°C and an optimum pH of 6.2. Determine the effect of the following on its rate of reaction 1) no change 2) increase 3) decrease A. 2 Increasing the concentration of sucrase B. 3 Changing the pH to 4 C. 3 Running the reaction at 70°C Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 31 19.8 -19.9 Enzyme Regulation: Inhibition Inhibitors: Are molecules that cause a loss of catalytic activity. Prevent substrates from fitting into the active sites. E+S ES E+P E+I EI no P Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 32 Reversible Competitive Inhibition A competitive inhibitor: Has a structure like the substrate. Competes with the substrate for the active site. Has its effect reversed by increasing substrate concentration. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 33 Noncompetitive, irreversible inhibition Inhibition A noncompetitive inhibitor: Has a structure different than the substrate. Distorts the shape of the enzyme, which alters the shape of the active site. Prevents the binding of the substrate. Cannot have its effect reversed by adding more substrate. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 34 Malonate and Succinate Dehydrogenase Malonate: Is a competitive inhibitor of succinate dehydrogenase. Has a structure that is similar to succinate. Inhibition is reversed by adding succinate. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 35 Learning Check Identify each description as an inhibitor that is: 1) Competitive 2) Noncompetitive A. Increasing substrate reverses inhibition. B. Binds to enzyme surface, but not to the active site. C. Structure is similar to substrate. D. Inhibition is not reversed by adding more substrate. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 36 Solution Identify each description as an inhibitor that is: 1) Competitive 2) Noncompetitive A. 1 Increasing substrate reverses inhibition. B. 2 Binds to enzyme surface, but not to the active site. C. 1 Structure is similar to substrate. D. 2 Inhibition is not reversed by adding more substrate. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 37 Zymogens Zymogens (proenzymes): Are inactive forms of enzymes. Are activated when one or more peptides are removed. Such as proinsulin is converted to insulin by removing a small peptide chain. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 38 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 39 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 40 Digestive Enzymes Digestive enzymes are: Produced as zymogens in one organ and transported to another when needed. Activated by removing small peptide sections. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 41 Allosteric Regulator Enzymes An allosteric enzyme is an enzyme That regulates the activity of an enzyme A positive regulator enhances the binding of substrate and the enzyme therefore, it accelerates the rate of reaction. A negative regulator changes the activity site so that the enzyme becomes less effective catalyst and rate slows down. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 42 A positive regulator changes the activity site so that the enzyme becomes a better catalyst and rate accelerates. A negative regulator changes the activity site so that the enzyme becomes less effective catalyst and rate slows down. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 43 Feedback Control In feedback control: A product acts as a negative regulator. An end product binds with the first enzyme (E1) in a sequence, when sufficient product is present. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 44 Learning Check Identify each statement as: 1) zymogen 2) allosteric enzyme 3) positive regulator 4) feedback control A. An enzyme in a pathway that controls the rate of the reaction. B. Speeds up a reaction by combining with an enzyme in the pathway. C. Removal of a peptide activates the enzyme. D. Some product binds to the first enzyme to limit the production of product. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 45 Solution Identify each statement as: 1) zymogen 2) allosteric enzyme 3) positive regulator 4) feedback control A. 2 An enzyme in a pathway that controls the rate of the reaction. B. 3 Speeds up a reaction by combining with an enzyme in the pathway. C. 1 Removal of a peptide activates the enzyme. D. 4 Some product binds to the first enzyme to limit the production of product. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 46 Enzyme Cofactors and Coenzymes A simple enzyme is an active enzyme that consists only of protein. Many enzymes are active only when they combine with cofactors such as metal ions or small molecules. A coenzyme is a cofactor that is a small organic molecule such as a vitamin. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 47 Enzyme Cofactors Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 48 Metal Ions as Cofactors Many active enzymes require a metal ion. Zn2+, a cofactor for carboxypeptidase, makes a cooordinate bond with the carbonyl oxygen and catalyzes the hydrolysis of a peptide bond. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 49 Some Enzymes and Their Cofactors Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 50 Learning Check Identify each enzyme as: 1) A simple enzyme 2) An enzyme that required a cofactor A. Requires Mg2+ for hydrolysis of phosphate esters. B. Requires vitamin B3 to transfer an acetyl group. C. Is active with four polypeptide subunits. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 51 Solution Identify each enzyme as: 1) A simple enzyme 2) An enzyme that required a cofactor A. 2 Requires Mg2+ for hydrolysis of phosphate esters. B. 2 Requires vitamin B3 to transfer an acetyl group. C. 1 Is active with four polypeptide subunits. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 52 Function of Coenzymes A coenzyme prepares the active site for catalytic activity. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 53 19.10 Water-Soluble Vitamins Water-soluble vitamins are: Soluble in aqueous solutions. Used as cofactors by many enzymes. Not stored in the body. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 54 Fat-Soluble Vitamins Fat-soluble vitamins: Are A, D, E, and K. Soluble in lipids, but not in aqueous solutions. Important in vision, bone formation, antioxidants, and blood clotting. Stored in the body. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 55 Learning Check Identify each compound as a: 1) water-soluble vitamin 2) fat-soluble vitamin A. Folic acid B. Retinol (Vitamin A) C. Vitamin C D. Vitamin E E. Niacin Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 56 Solution Identify each compound as a: 1) water-soluble vitamin 2) fat-soluble vitamin A. 1 Folic acid B. 2 Retinol (Vitamin A) C. 1 Vitamin C D. 2 Vitamin E E. 1 Niacin Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 57 Thiamin (Vitamin B1) Thiamin: Was the first B vitamin identified. Is part of the coenzyme thiamin pyrophosphate. TPP coenzyme is required by enzymes in the decarboxylation of α-keto carboxylic acids. Deficiency results in beriberi (fatigue, weight loss, and nerve degeneration). Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 58 Riboflavin (Vitamin B2) Riboflavin is: Made of ribitol and flavin. Part of the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). Needed for good vision and healthy skin. O H3C N H3C N N N H O D-Ribitol CH2 CH CH CH CH2 OH OH OH OH Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 59 Niacin (Vitamin B3) Niacin: Is part of the coenzyme nicotinamide adenine dinucleotide (NAD+) involved in oxidationreduction reactions. Deficiency can result in dermatitis, muscle fatigue, and loss of appetite. Is found in meats, rice, and whole grains. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. O C OH N 60 Pantothenic Acid (Vitamin B5) Pantothenic acid: Is part of coenzyme A needed for energy production as well as glucose and cholesterol synthesis. Deficiency can result in fatigue, retarded growth, cramps, and anemia. Is found in salmon, meat, eggs, whole grains, and vegetables. CH3 OH O HO CH2 C CH3 O CH C N CH2 CH2 C OH H Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 61 Pyridoxine (Vitamin B6) Pyridoxine and pyridoxal are two forms of vitamin B6, which are converted to the coenzyme pyridoxal phosphate (PLP). PLP is required in the transamination of amino acids and decarboxylation of carboxylic acids. Deficiency of pyridoxine may lead to dermatitis, fatigue, and anemia. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 62 Cobalamin (Vitamin B12) Cobalamin: Consists of four pyrrole rings with a Co2+. Is a coenzyme for enzymes that transfer methyl groups and produce red blood cells. Deficiency can lead to pernicious anemia and nerve damage. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 63 Ascorbic Acid (Vitamin C) Vitamin C: Is required in collagen synthesis. Deficiency can lead to weakened connective tissue, slow-healing wounds, and anemia. Is found in blueberries, citrus fruits, tomatoes, broccoli, red and green vegetables. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. CH2OH O HO O CHOH OH 64 Folic Acid (Folate) Folic acid (folate): Consists of pyrimidine, p-aminobenzoic acid, and glutamate. Forms the coenzyme THF used in the transfer of carbon groups and the synthesis of nucleic acids. Deficiency can lead to abnormal red blood cells, anemia, and poor growth. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 65 Vitamin A Vitamin A is obtained from meats and betacarotenes in plants. Beta-carotenes are converted by liver enzymes to vitamin A (retinol). H3C Beta-carotene CH3 CH3 CH3 CH3 CH3 H3C H3C CH3 CH3 CH3 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. CH3 H3C CH3 CH3 CH2OH Retinol (vitamin A) 66 Vitamin D Vitamin D (D3): Is synthesized in skin exposed to sunlight. Regulates the absorption of phosphorus and calcium during bone growth. Deficiency can result in weakened bones. Sources include cod liver oil, egg yolk, and enriched milk. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 67 Vitamin E Vitamin E: Is an antioxidant in cells. May prevent the oxidation of unsaturated fatty acids. Is found in vegetable oils, whole grains, and vegetables. CH3 HO CH3 H3C CH3 O CH3 CH3 CH3 CH3 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 68 Vitamin K Vitamin K1 in plants has a saturated side chain. Vitamin K2 in animals has a long unsaturated side chain. Vitamin K2 is needed for the synthesis of zymogens for blood clotting. O O CH3 CH3 CH3 CH3 3 O CH3 CH3 Vitamin K1 (phylloquinone) Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. n O CH3 CH3 Vitamin K2 (menaquinone) 69 Learning Check Identify the vitamin associated with each: 1) Thiamin (B1) 2) Vitamin A 3) Vitamin K 4) Vitamin D 5) Ascorbic Acid A. B. C. D. E. Collagen formation Beriberi Absorption of phosphorus and calcium in bone Vision Blood clotting Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 70 Solution Identify the vitamin associated with each: 1) Thiamin (B1) 2) Vitamin A 3) Vitamin K 4) Vitamin D 5) Ascorbic Acid A. B. C. D. E. 5 1 4 2 3 Collagen formation Beriberi Absorption of phosphorus and calcium in bone Vision Blood clotting Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 71 Chapter Summary Enzymes are catalysts for biochemical reactions. Enzymes are mostly water soluble and globular. Many enzyme require a co-factor that are metal ions or non-protein organic molecules known as coenzymes. There are six major classes of reactions catalyzed by enzymes. Enzymes draws substrates into its active site and hold them in its active site by non-covalent interactions to produce enzyme-substrate complex. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 72 Chapter Summary Contd. Reactions take place within the enzyme-substrate complexes. When the reaction is over, product is released and the enzyme returns to its original conditions. With increasing temperature, rate of enzyme catalyzed reactions increases to a maximum and then starts to decrease as the enzyme protein denatures at high temperature. Enzyme catalyzed reaction rate is maximal at an optimum pH. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 73 Chapter Summary Contd. The effectiveness of enzymes is controlled by a variety of activation and inhibition mechanisms. Vitamins are organic molecules required in small amounts in the diet because our body can not synthesize them. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 74 Terms Carcinoma In medicine, carcinoma is any cancer that arises from epithelial cells. It is malignant by definition: carcinomas invade surrounding tissues and organs, and may spread to lymph nodes and distal sites (metastasis). Carcinoma in situ (CIS) is a pre-malignant condition, in which cytological signs of malignancy are present, but there is no histological evidence of invasion through the epithelial basement membrane. Rickets is a disorder most commonly caused by Vitamin D deficiency. This results in insufficient calcium uptake by bones in developing children. The lack of calcium being absorbed into the body,causes fragile or malformed bones, which are unable to support the weight of a growing body. Calcium or phosphorus deficiency in children is termed rickets, while that of adults is termed osteomalacia. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 75 Terms pH of small intestine: Each digestive enzyme works best at an optimum pH. The stomach has a pH of about 2, while the small intestine has a pH of between 7 and 8 . Thrombin is a coagulation protein that has many effects in the coagulation cascade. It is a serine protease that converts soluble fibrinogen into insoluble strands of fibrin . Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 76 Epithelial Cells: In zootomy, epithelium is a tissue composed of a layer of cells. Epithelium lines both the outside (skin) and the inside (e.g. intestine) of organisms. The outermost layer of our skin is composed of dead squamous epithelial cells, as are the mucous membranes lining the inside of mouths and body cavities. Other epithelial cells line the insides of the lungs, the gastrointestinal tract, the reproductive and urinary tracts, and make up the exocrine and endocrine glands. Functions of epithelial cells include secretion, absorption, protection, transcellular transport, sensation detection, and selective permeability. Endothelium (the inner lining of blood vessels) is not related to epithelium except by name. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 77 Terms Thrombin:is a coagulation protein that has many effects in the coagulation cascade. It is a serine protease that converts soluble fibrinogen into insoluble strands of fibrin. Anemia or anaemia, which literally means "without blood," is a deficiency of red blood cells and/or hemoglobin. This results in a reduced ability of blood to transfer oxygen to the tissues, and this causes hypoxia; since all human cells depend on oxygen for survival, varying degrees of anemia can have a wide range of clinical consequences Pyrrole Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 78 Terms Vitamin B12,: available as food supplement Folic Acid: found in food Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 79 Vitamin K1 Phylloquinone is a polycyclic aromatic ketone, based on 1,4naphthoquinone, with 2-methyl and 3-phytyl substituents. It is often called vitamin K1. It is a fat-soluble vitamin that is stable to air and moisture but decomposes in sunlight. It is found naturally in a wide variety of green plants. Vitamin K denotes a group of 2-methilo-naphthoquinone derivatives. They are human vitamins, lipophilic (i.e., soluble in lipids) and therefore hydrophobic (i.e., poorly soluble in water). They are needed for the posttranslational modification of certain proteins, mostly required for blood coagulation. Vitamin K2 (menaquinone, menatetrenone) is normally produced by bacteria in the intestines, and dietary deficiency is extremely rare unless the intestines are heavily damaged. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 80 End of Chapter Nineteen Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 81