Temperature Regulation Chapter 25 Nutrition, Metabolism, Temperature Regulation

Nutrients Chemicals used by body Classes Food Guide Pyramid Carbohydrates, proteins, lipids, vitamins, minerals, water Food Guide Pyramid USDA recommends Kilocalories Measure of energy supplied by food and released through metabolism

Carbohydrates Monosaccharides Disaccharides Polysaccharides (complex) Include glucose, fructose, galactose Disaccharides Include sucrose, maltose, lactose Polysaccharides (complex) Include starch, glycogen, cellulose Disaccharides and Polysaccharides Converted to glucose (used for energy or stored as glycogen or fats)

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

Proteins Chains of amino acids Functions Kinds Essential (9): Must be obtained in diet Nonessential: Body can synthesize Functions Protection (antibodies), regulation (enzymes, hormones), structure (collagen), muscle contraction (actin, myosin), transportation (hemoglobin, ion channels)

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

Vitamins Function as coenzymes or parts of coenzymes Organic molecules that exist in minute quantities in food Essential vitamins must be obtained by diet Classifications Fat soluble: Vitamins A,D,E,K Water-soluble: B and C

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 Obtained from animal and plant sources

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

Catabolic and Anabolic Reactions

Cellular Metabolism

Carbohydrate Metabolism Glycolysis Breakdown of glucose into 2 pyruvic acid molecules Phases Input of ATP Sugar cleavage NADH production ATP and pyruvic acid production

Glycolysis

Glycolysis

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 Cori cycle Process of converting lactic acid to glucose

Aerobic Respiration Breakdown of glucose in presence of oxygen to produce carbon dioxide, water, 38 ATP molecules Most of ATP molecules to sustain life are produced this way Phases Glycolysis, acetyl-CoA formation, citric acid cycle, electron-transport chain

Aerobic Respiration

Electron-Transport Chain

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

Protein Metabolism New amino acids are formed by transamination, transfer of an amine group to keto acid Amino acids are used to synthesize proteins If used for energy, ammonia is produced as a by-product of oxidative deamination Ammonia is converted to urea and excreted

Amino Acid Metabolism Once absorbed in body, amino acids quickly taken up by cells Amino acids are used to synthesize proteins or as a source of energy Amino acids not stored in body

Amino Acid Reactions

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

Interconversion of Nutrient Molecules

Metabolic States Absorptive state Postabsorptive 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

Absorptive State

Postabsorptive State

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%

Body Temperature Regulation A balance between heat gain and loss Heat is produced through metabolism Heat is exchanged through radiation, conduction, convection, evaporation The greater the temperature difference between body and environment, the greater the rate of heat exchange Regulated by a “set point” in hypothalamus

Heat Exchange

Temperature Regulation