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Body Functioning

Body Functioning. Chapter 24. Nutrition. Nutrients. Substances to promote/enable life Categories Major nutrients (carbs, lipids, and proteins) Vitamins and minerals Water Essential nutrients can’t be made ourselves. Carbohydrates. Primarily from plants

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Body Functioning

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  1. Body Functioning Chapter 24

  2. Nutrition

  3. Nutrients • Substances to promote/enable life • Categories • Major nutrients (carbs, lipids, and proteins) • Vitamins and minerals • Water • Essential nutrients can’t be made ourselves

  4. Carbohydrates • Primarily from plants • Complex carbohydrates (e.gpolysaccharides or starches) • Bread, cereal, pasta, vegetables, potatoes • Simple carbohydrates (e.gmonosaccharides or sugars) • Pop, candy, fruit, ice cream, fruits • Glucose is basic form and fuel source (4kcal/g) • Excess stored as glycogen and fat • 45 – 60% daily calories recommended • Protein and fat used when less

  5. Lipids • Triglycerides (fats) • Unsaturated (vegetable fats/oils) and saturated (animal fats/solids) • Protect, cushion, insulate, and fuel source (9kcal/g) • Cholesterol • Egg yolk, meat, shellfish, milk products • Stabilizes PM and precursor for steroid hormones and bile salts • Essential fatty acids (linoleic and linolenic acids) • Found in most vegetable oils • Prostaglandin production • 20 – 35% daily calories

  6. Proteins • Complete (animal products) • Eggs, milk, fish, meats • Have all essential AA’s for maintenance and growth • Incomplete (plant products) • Legumes, seeds, vegetables, grains • Lack 1 or more AA’s • Vegetarian diets and rice w/bean diets • Structural materials • Keratin, collagen, elastin, muscle fibers • Functional uses • Enzymes, hormones, hemoglobin • 12 – 20 % daily calories

  7. Protein Use Determination • All-or-none rule • AA’s not stored • Protein synthesis requires all AA’s needed present • Caloric intake • Fuel (4kcal/g) w/ insufficient carbs or fats • Nitrogen balance • Ingestion = excretion • Positive w/ synthesis > breakdown (growth & repair) • Negative w/ breakdown > synthesis (starvation & injury) • Hormones • Anabolic hormones (GH & sex hormones) accelerate synthesis • Stress (glucocorticoids) accelerate breakdown

  8. Vitamins • Organic molecules needed in small amounts • Water soluble, • B-complex and C absorbed in GI tract w/water • B12 needs intrinsic factor from stomach • Fat soluble • Vitamins A, D, E, and K absorbed in GI tract w/ source • Obtained in most foods • Coenzymes in the body • Most are essential • Vitamin D (skin) and K (intestines) are exceptions • Table 24.2

  9. Minerals • Inorganic molecules needed by the body • Major needed in moderate amounts • Ca2+, phosphorus, K+, sulfur, Na+, Cl-, Mg2+ • Minor needed in trace amounts • Iron, iodine, fluorine, zinc • Vegetables, legumes, milk, and meats = good • Refined cereals, fats, sugars, and grains = poor • Ca2+, phosphate, and Mg2 harden bone • Na+ and Cl- for nerve and muscle fxnand H2O balance • Table 24.3

  10. Metabolism

  11. Metabolism (review) • All chemical reactions necessary for life • Reaction types • Anabolic: build up/synthesis • AA + AA + …  polypeptide • Catabolic: break down/hydrolyze • Starch  glucose + glucose + … • Cellular respiration (glucose catabolism) • Redox reactions • Oxidation: lose electron/energy* (LEO) by dehydrogenase • Reduction: gain electron/energy* (GER) by oxidases • Phosphorylation • Addition of a phosphate group (PO3-) to activate • ADP + P ATP • Substrate-level or oxidative

  12. Metabolizing Nutrients (overview) • Stage 1 • Digestion and absorption in GI tract • Stage 2 • Anabolic and/or catabolic processing in tissues • Glycoysis • Stage 3 • Stage 2 products catabolized in mitochondria • Kreb’s cycle and oxidative phosphorylation • Fig 24.3

  13. Glucose Catabolism (overview) • Aerobic use of primary fuel source • Overall reaction C6H12O6 + 6O26H2O + 6CO2 + 36-38 ATP + heat • Overall process • Glycolysis (cytoplasm) • Glucose  pyruvate + NADH + 2 (net) ATP • Kreb’s Cycle (mitochondria) • Pyruvate  CO2 + NADH + FADH2 + 2 ATP • Oxidative phosphorylation (mitochondria) • ETC and chemiosmosis • NADH + FADH2 + O2 H2O + 36 -38 ATP • Fig 24.5

  14. Glycolysis • Aerobic or anaerobic conditions • In the cytoplasm • Starts with: • Glucose (6C’s) • 2 ATP • Ends with: • 2 pyruvate (3C’s) or • Lactic acid or CO2 and EtOH • Important products of this process: • Net 2 ATP • 4 ATP  substrate-level phosphorylation • 2 NADH

  15. Transition • Cytoplasm to mitochondria • Starts with: • 2 Pyruvate (3C’s) • Ends with: • 2 Acetyl-CoA (2C’s) • Important products of this process: • 2 CO2 Decarboxylation • 2 NADH

  16. Kreb’sCycle • In the mitochondrial matrix CYCLE SEEN OCCURS TWICE • Starts with: • 2 Acetyl CoA • Ends with: • 4 CO2 • Important products of this process: • 2 ATP  substrate level phosphorylation • 6 NADH • 2 FADH2 6 C’s 4 C’s 4 C’s

  17. Oxidative Phosphorylation: Electron Transport Chain (ETC) • In the inner mitochondrial membrane (cristae) • Starts with: • 10 NADH (2 glycolysis, 2 transition, and 4 Kreb’s cycle) • 2 FADH2 (citric acid cycle) • 6 O2 (final e- acceptor) • Ends with: • H2O • Important products of this process: • H + gradient

  18. Oxidative Phosphorylation: Chemiosmosis • In the inner mitochondrial membrane (cristae) • Starts with: • H + gradient • Ends with: • 32 – 34 ATP • ATP synthase facilitates

  19. A Review of Glucose Catabolism Substrate level phosphorylation

  20. Regulating Glucose Levels • High glucose and/or lots of ATP inhibits glucose catabolism • Body unable to store ATP • Glucose converted to glycogen for storage • In liver and skeletal muscle storage = glycogenesis • Drop in glucose signals glycogenolysis • Glycogen (liver) catabolized to glucose • Low glucose levels signal gluconeogenesis • New glucose from non-carbs (fat and protein) in liver

  21. Lipid Catabolism • Triglycerides from GI tract, as chylomicrons (soluble lipids) • Glycerol pathway • Glycerol  glycolysis intermediate  glucose catabolism (glycolysis start) • ½ glucose molecule ~ 16 ATP • Fatty acid pathway • FA’s  acetic acid  glucose catabolism (Kreb’s start) • FA’s  NADH and FADH2 • More compact energy source w/ 2X’s more PE

  22. Lipids and Adipose Tissue • High ATP and glucose stimulates lipogenesis • Synthesis of triglycerides for liver & adipose storage • High ATP = excess glycolysis intermediates • Converted into lipogenesis pathway • Excess carbs, but low fat diet = fat storage • Glucose deficiency stimulates lipolysis (liver, cardiac & skeletal muscle) • Breakdown of stored fat • Severe depletion causes ketogenesis • Incomplete breakdown of fats produce ketones • Lowers blood pH causing ketosis

  23. Protein Metabolism • Protein catabolism oxidizes AA’s for energy • Transamination: NH2 (amine) to Kreb’s intermediate • Liver uses for non-essential AA synthesis • Oxidative deamination: NH2 removed as NH3 (ammonia) • Combine w/ CO2 (liver) to detoxify = urea and H2O • Keto acid modification: alters intermediate for Kreb’s entry • Protein anabolism or fat storage • All-or-none rule (earlier) • Otherwise become energy fuels

  24. Energy Regulation

  25. Heat Exchange • From variations between skin and external environment • Types • Radiation • Heat transfer b/w 2 objects not in contact w/ each other • Body heat in rooms or sunbathing • Conduction • Heat transfer b/w 2 objects in contact w/each other • Entering a hot tub or sitting in a seat • Convection • Heat transfer b/c density (heat rises = less dense) • Fan direction in summer (air up) vs winter (air down) • Evaporation • Heat transfer b/c H2O molecules evaporate • Sweating

  26. Heat Production • From low temps. in external environment or blood • Mechanisms • Vasoconstriction: reduces superficial blood flow to reduce shell loss • Frostbite when extended from decreased O2 and nutrients • Shivering: involuntary relax/contract of muscles • Metabolic increase: Epi and NE release increased • Increased thyroxine release: increases metabolic rate • Behavioral changes: add layers/blankets, drinkhot beverages, increase activity levels • Hypothermia when sluggish enzymes decreasing mechanisms

  27. Heat Loss • From high internal temps • Mechanisms • Types of heat exchange (previous) • Vasodilation: inhances superficial blood flow to increase shell loss • Sweating: perspiration to enhance evaporation • Ineffective w/ high humidity (the South) • Behavioral: finding shady spots/fans, reduce activity, looser/lighter/less clothing • Hyperthermia depresses hypothalamus (control) • Positive feedback mechanisms can cause heat stroke when mechanisms fail otherwise = heat exhaustion

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