Chapter 16 Nutrition and Metabolism Nutrition food nutrients
§ Chapter 16 - Nutrition and Metabolism § Nutrition - food (nutrients) we eat l Need balance - carbohydrates, fats, proteins (vitamins & minerals) l Malnutrition - deficiency or imbalance in consumption of nutrients § Metabolism - the “use of foods, ” after they have been digested, absorbed, & circulated to cells
§ Use food products in two ways l l energy source building blocks for complex chemical compounds § Assimilation - occurs when food molecules enter cells & undergo chemical changes § Catabolism - chemical reactions that release energy from food l body’s only source of energy
§ Anabolism - chemical reactions that build food molecules into more complex chemical compounds § Role of the Liver l l l Bile -secreted to help move fats (lipids) Help maintain normal glucose conc. Synthesize blood proteins (plasma proteins prothrombin, fibrinogen, albumin) Detoxifies bacterial products & some drugs Stores iron, Vitamin A & D Blood flow from GI tract goes to liver 1 st
§ Carbohydrate Metabolism l l Preferred energy source Compound made of glucose which body likes to use 1 st for energy § Three series of chemical reactions that occur in sequence for catabolism of glucose: l l 1. Glycolysis - changes glucose to pyruvic acid (in cytoplasm), anaerobic, energy is released 2. Citric acid cycle - pyruvic acid to carbon dioxide (in mitochondria), aerobic, energy is released
l 3. Electron transfer system • Located in mitochondria • Transfers most of glucose energy to ATP (adenosine triphosphate), some as heat • ATP - served as direct energy source for cellular work in all living organisms • ATP - not stored - used almost immediately • When ATP used - it changes to a reusable form (ADP) & releases energy - ADP attached to more carbohydrate breakdown products > forms more ATP • Only enough ATP is produced to met cellular
§ Glycogenesis - glucose anabolism l l Occurs in liver & muscle cells Process of joining glucose molecules together > glycogen (animal starch) § Constant Glucose Blood Levels l l Stays between 70 - 110 mg / 100 ml blood (even if we have or have not eaten) Hormones help regulate carbohydrate metabolism to control blood glucose • Insulin - helps glucose into cells (< blood levels)
§ Fat Metabolism l l l Also primary source of energy Used if glucose not available - fats can goes into citric acid cycle for energy If not needed - anabolized to form triglycerides stored in adipose tissue § Protein Metabolism l l Used for energy only in very small amounts (normally) Anabolism - amino acids (20) used to make proteins (Essential - must be in diet, Nonessentialcan be missing from diet, body can make)
§ Vitamins l l l Organic compounds needed in small amt. for normal metabolism throughout the body Make enzymes work properly Most are not made in body (must come from diet) Body stores fat-soluble Vit. -A, D, E, K in the liver Water-soluble (Vit. Bs, C) - need continuous supply from diet
l l Avitaminosis - deficiency of vitamins • Scurvy - deficiency Of Vit. C, < collagen fiber production & maintenance = body falls apart (connective tissue problems) Hypervitaminosis - vitamin excess • Vit. A - Hair loss, skin dry, anoxexia, vomiting • More common with fat-soluble vit. § Minerals - inorganic elements or salts found naturally in the earth - proper amt. l Enzymes activation, many chemical reactions (Na & Ca: muscle & nerve conduction)
§ Metabolic Rates § Basal metabolic rate (BMR) - rate at which food is catabolized under basal conditions (resting but awake, not digesting food, not adjusting to temp. ) l Number of calories of heat that must be produced per hour by catabolism to keep body alive, awake, & comfortably warm § Total metabolic rate (TMR) - total amt. of energy used by body / day § Calories = TMB (no weight gain)
§ Body Temperature l l 60% energy from food > heat (not ATP) Hypothalamus regulates body temp. by negative feedback mechanisms (^ temp. > more blood to skin) Normal 97 -100 degrees F Heat lost from skin: • Radiation - flow of heat away from blood • Conduction - transfer to skin > external envir. • Convection - transfer to air(flowing away from skin) • Evaporation - water (sweat) vaporization l Heat Conserved - vasoconstriction
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