25-1 Rod R. Seeley Idaho State University Trent D. Stephens Idaho State University Philip Tate Phoenix College Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. *See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. Chapter 25 Lecture Outline *

25-2 Chapter 25 Nutrition, Metabolism, and Temperature Regulation

25-3 Nutrients Chemicals used by body to produce energy, provide building blocks or function in other chemical reactions Classes –Carbohydrates, proteins, lipids, water: required in large amounts –Vitamins, minerals: required in small amounts –Food Guide Pyramid: USDA recommendations Essential nutrients: must be ingested, cannot be synthesized. Certain amino acids, certain fatty acids, most vitamins, minerals, water, and a minimum number of carbohydrates Kilocalories: measure of energy supplied by food and released through metabolism

25-4 Carbohydrates Most come from plants (exception lactose from milk) Monosaccharides: include glucose, fructose, galactose Disaccharides: include sucrose, maltose, lactose Polysaccharides (complex): include starch, glycogen, cellulose. Cellulose is indigestible Disaccharides and Polysaccharides: converted to glucose (used for energy or stored as glycogen or fats)

25-5 Carbohydrates: Uses in the Body Digestion breaks poly- and disaccharides into monosaccharides before absorption Liver converts monosaccharides into glucose which is then used as an energy source to produce ATP Excess glucose converted to glycogen and stored in muscles and liver cells Excess beyond storage is converted to fat Sugars also become part of DNA, RNA, and ATP, glycoproteins, glycolipids

25-6 Lipids Triglycerides (95%): used for energy to produce ATP or stored in adipose tissue, liver –Saturated fats: meat fats, whole milk, cheese, eggs –Unsaturated fats: olive and peanut oil Cholesterol: steroid found in liver, egg yolks but not found in plants Phospholipids: major components of plasma membranes Linoleic acids: essential fatty acids. Found in seeds, nuts, legumes, grains and green leaves

25-7 Uses of Lipids in the Body Triglycerides: used to produce ATP Excess stored in adipose tissue or liver. Cholesterol: can be eaten or manufactured in the body. Component of plasma membranes, can be modified to form bile salts and steroids Eicosanoids derived from fatty acids. Involved in inflammation, blood clotting, tissue repair, smooth muscle contraction. Phospholipids: part of plasma membrane and used to construct the myelin sheath. Part of bile

25-8 Proteins Chains of amino acids –Types Essential: must be obtained in diet Nonessential: body can synthesize Complete proteins: contain all necessary amino acids (meat, fish, poultry, milk, cheese, eggs) Functions –Protection (antibodies), regulation (enzymes, hormones), structure (collagen), muscle contraction (actin, myosin), transportation (hemoglobin, ion channels)

25-9 Recommended Amounts Carbohydrates –60% of daily intake of kilocalories Lipids –30% or less of total daily kilocalories Proteins –10% of total kilocalories per day

25-10 Vitamins Function as coenzymes or parts of coenzymes (combine with enzymes and make the enzyme functional) Organic molecules that exist in minute quantities in food –Essential vitamins must be obtained by diet –Provitamins: substance that can be assembled by the body into a functioning vitamin. Classifications –Fat soluble: A, D, E, K. Can be stored in fatty tissues to the point of toxicity. Too much A causes bone and muscle pain; skin disorders, hair loss, increased liver size. Too much D causes deposition of Ca in kidneys, heart, blood vessels. –Water-soluble: B, C, and all others. Remain short time then are excreted. Too much C causes stomach inflammation; diarrhea. Antioxidants: prevent formation of free radicals. Free radicals are chemicals produced by metabolism that are missing electrons. They take electrons from chemicals in cells, damaging the cells.

25-11 Minerals Inorganic, necessary for normal metabolic functions Functions: establish resting membrane potentials, generate action potentials, add strength to bones and teeth, buffers, involved in osmotic balance; are components of coenzymes, vitamins, hemoglobin. Obtained from animal and plant sources. Minerals attached to plant fibers are difficult to absorb.

25-12

25-13 Daily Values Percent daily values related to energy consumption based on a 2000 kcal/day diet

25-14 Metabolism Total of all chemical changes that occur in body –Catabolism: energy-releasing process where large molecules broken down to smaller –Anabolism: energy-requiring process where small molecules joined to form larger molecules Energy in carbohydrates, lipids, proteins is used to produce ATP through oxidation- reduction reactions

25-15 ATP Coupling of Catabolic and Anabolic Reactions

25-16 ATP Synthesis

25-17 Carbohydrate Metabolism: Glycolysis

25-18 Carbohydrate Metabolism: Glycolysis

25-19 Carbohydrate Metabolism: Glycolysis

25-20 Carbohydrate Metabolism: Glycolysis

25-21 Anaerobic Respiration Breakdown of glucose in absence of oxygen –Produces 2 molecules of lactic acid and 2 molecules of ATP Phases –Glycolysis –Lactic acid formation

25-22 Aerobic Respiration Breakdown of glucose in presence of oxygen to produce carbon dioxide, water, 38 ATP molecules –Most of ATP molecules that sustain life are produced this way Phases –Citric acid cycle, electron-transport chain

25-23 Aerobic Respiration

25-24 The Citric Acid Cycle

25-25 Electron-Transport Chain

25-26 Lipid Metabolism Adipose triglycerides are broken down and released as free fatty acids Free fatty acids are taken up by cells and broken down by beta-oxidation into acetyl- CoA which: –Can enter citric acid cycle –Can be converted to ketone bodies (ketogenesis) in liver. Ketones travel to skeletal muscle and are used in citric acid cycle to produce ATP

25-27 Protein Metabolism Non-essential amino acids can be formed by transamination, transfer of an amine group to keto acid. Can also be eaten. Amino acids are used to synthesize proteins If used for energy, amino acids undergo oxidative deamination. Ammonia and keto acids are produced as by-products of oxidative deamination. Ammonia is converted to urea and excreted. Amino acids not stored in the body

25-28 Amino Acid Metabolism

25-29 General Formulas of an Amino Acid and a Keto Acid

25-30 Amino Acid Reactions

25-31 Interconversion of Nutrient Molecules Glycogenesis –Excess glucose used to form glycogen Lipogenesis –When glycogen stores filled, glucose and amino acids used to synthesize lipids Glycogenolysis –Breakdown of glycogen to glucose Gluconeogenesis –Formation of glucose from amino acids and glycerol

25-32 Interconversion of Nutrient Molecules

25-33 Metabolic States Absorptive state: period immediately after eating when nutrients absorbed through intestinal wall into circulatory and lymphatic systems (about 4 hours after each meal) Postabsorptive state: occurs late in morning, afternoon, night after absorptive state concluded –Blood glucose levels maintained by conversion of other molecules to glucose

25-34 Absorptive State

25-35 Postabsorptive State

25-36 Metabolic Rate Total amount of energy produced and used by body per unit of time –Estimated by amount of oxygen used per minute Components –Basal metabolic rate: energy used at rest, 60% of metabolic rate –Thermic effect of food: energy used to digest and absorb food, 10% –Muscular activity: energy used for muscle contraction, 30%

25-37 Body Temperature Regulation Free energy: total amount of energy liberated by the complete catabolism of food. –43% used to produce ATP –57% lost as heat A balance must be maintained between heat gain and loss –Heat is produced through metabolism –Heat is exchanged through radiation (loss of heat as infrared radiation), conduction (exchange of heat between objects in direct contact with each other), convection (transfer of heat between the body and the air), evaporation (conversion of water from a liquid to a gaseous form) The greater the temperature difference between body and environment, the greater the rate of heat exchange Regulated by a “set point” in hypothalamus. Negative feedback mechanism. Set point can change; e.g., during a fever

25-38 Temperature Regulation