Nutrition, Metabolism and Thermoregulation

1. Nutrition, Metabolism and Thermoregulation

2. Metabolism of Energy containing Nutrients

3. Nutrition • We eat, we digest, we absorb, then what? • 3 fates for food = nutrients • Most are used to supply energy for life • Some are used to synthesize structural or functional molecules • The rest are stored for future use – love handles!

4. Nutrition Out of Date Figure 24.1

5. Nutrition: The Recommendation .

6. Nutrition for College Students Four Groups: Grease Salt Sugar Alcohol

7. Protein Nutrition Essential amino acids are the 9 (out of ~20) that we cannot synthesize in the liver by transamination; they must be present in our diet. All amino acids can be broken down for ATP energy production. .

8. Nutrition • Summary of Carbohydrate, Lipid and Protein Nutrients (Table 24.1, p945) • Vitamins (Table 24.2, p948-941) • Function as coenzymes • Not made in body (xcept D by skin, some B&K by intestinal bacteria) • B vitamins • Minerals (Table 24.3, p952-955) • 4% body weight • Ionized in body fluids/bound to organic compounds (phospholipids, hemoglobin, Na+Cl-)

9. Metabolism • All biochemical reactions in the body • Balance between synthesis (anabolic) and breakdown (catabolic) reactions • Anabolism • chemical reactions that combine simple, smaller molecules into more complex molecules • uses energy • protein formation from amino acids • carbohydrate formation from simple sugars • Catabolism • chemical reactions that break down complex organic molecules into simpler ones • releases energy • proteins are broken down by various proteases

10. Metabolism (cont) • Relationship of catabolism to anabolism

11. Metabolism (cont) • Link between anabolism and catabolism is ATP • ATP energy is the “currency” used in most cellular energy exchanges • Catabolic reactions provide the ATP energy that most anabolic reactions require • Only about 10-30% of the energy released by catabolic reactions can be used • most chemical energy is lost as “waste heat” • “waste heat” is not wasted; it is essential in maintaining a constant body temperature

12. Metabolism (cont) • ATP • Allows for transfer of small but useful amounts of energy from one molecule to another • Cell's entire amount of ATP is recycled approximately every minute • ATP is NOT for long term energy storage • too reactive in the cell • other molecules available for energy storage (neutral fats, glycogen, creatine phosphate, etc.) • About 8kg (17 lb) of ATP is produced every hour in an average male • Total amount of ATP present in the body at any time is only about 50g (0.050 kg)

13. Metabolism (cont) • ATP (cont) • Energy is released by breaking the third phosphate group’s bond • ATP  ADP + Pi • a reversible reaction • the energy released is enough to drive anabolic reactions • ATP  ADP + CrP • creatine provides energy storage in skeletal muscle • allows for more ATP to be formed when O2 is less readily available during skeletal muscle contraction

14. ATP is composed of 3 things: • The sugar ribose • The base adenine • 3 phosphate groups These phosphates are the key to the activity of ATP.

15. Energy is stored by adding a phosphate to ADP • ADP + Pi  ATP • Energy stored (endogonic / endothermicrxn) • Energy is released by breaking a phosphate off ATP • ATPADP + Pi • Energy released (Exogonic/exothermic rxn)

16. Energy Production • Energy is stored in chemical bonds • Oxidation-Reduction (Redox) reactions: • Oxidation component: • also known as dehydrogenation reactions • remove electrons from molecules • decreases the energy remaining in the oxidized molecule • generally, 2e- (and 2H+) are removed simultaneously • Can also be the gain of oxygen

17. Energy Production (cont.) • Reduction component: • addition of electrons to a molecule • increases the energy of the reduced molecule • These 2 component reactions are always coupled: oxidation-reduction reactions

18. Oxidation Is Losing Electrons, Reduction Is Gaining Electrons: OIL RIG Electron Loss Means Oxidation: ELMO Losing Electrons Oxidation, Gaining Electrons Reduction: LEO the lion. GER! or LEO says GER

19. Energy Production (cont.) • ATP Generation • Addition of phosphate to a chemical compound is phosphorylation • 3 mechanisms for this: • Substrate level phosphorylation – a high-energy phosphate group is transferred directly from a molecule to ADP to make ATP For example, when the energy stored on a high-energy phosphate group on creatine phosphate is transferred to ADP to make ATP in skeletal muscles CK transfers a high energy phosphate from creatine phosphate to ADP

20. Energy Production (cont.) ATP Generation • Oxidative phosphorylation • electrons (H+) removed from molecules • enzymes combine H+ with O2, releasing enough energy for ATP formation • Photo-phosphorylation • photosynthesis

21. Carbohydrate Metabolism • General • 80% of carbohydrates ingested contain glucose; remainder: fructose, galactose • glucose is the body's preferred carbohydrate energy source • Fate of carbohydrates -- depends on needs of body cells • ATP production • Amino acid synthesis • Glycogenesis • Lipogenesis • Excretion in urine (minimal)

22. Carbohydrate Metabolism (cont.) • Glucose anabolism • Glucose storage: glycogenesis • glycogen formation is stimulated by insulin • glucose not needed immediately is stored in the liver (25%) and in skeletal muscle (75%) • Glucose release: glycogenolysis • converts glycogen to glucose • occurs between meals, stimulated by glucagon and epinephrine

23. Carbohydrate Metabolism (cont.) • Glucose anabolism (cont.) • Formation of glucose from proteins & fats: gluconeogenesis • When blood glucose level is low, you eat; if glucose remains low, body catabolizes some proteins and fats • Stimulated by cortisol and thyroid hormone • cortisol (glucocorticoids) mobilizes proteins, making AA's available • thyroid hormone mobilizes proteins (AA's) and may mobilize lipids • Epinephrine, glucagon, hGH also stimulate • These five hormones are often referred to as the “insulin antagonists.”

24. Glucose Catabolism • Glucose oxidation is known as cellular respiration • Complete catabolism of each molecule of glucose to CO2, H2O • Maximum yield of 38 ATP molecules/glucose • 38% of the energy present in a glucose • excellent efficiency for a biological system • the rest of the energy is “waste heat” • 2 linked enzymatic pathways are involved in glucose catabolism • glycolysis • Kreb’s cycle

25. Cells make ATP in an organelle called the mitochondria

26. In eukaryotes, respiration occurs in 3 steps 1. Glycolysis(sugar breaking) 2. Kreb’s Cycle (Citric Acid Cycle) 3. Electron Transport Chain

27. Glycolysis occurs in the cytosol of the cell and makes 2 ATP. • Glycolysis starts with the monosacchride (sugar) glucose • And uses the coenzyme NAD+

28. The Kreb’s cycle or (Citric Acid Cycle) occurs in the matrix of the mitochondria and makes 2ATP

29. The electron transport chain occurs across the inner membrane of the mitochondria. • It makes 34 ATP and requires oxygen • It only occurs in eukaryotes

30. Sometimes, under anaerobic (lack of oxygen) conditions, like strenuous exercise, eukaryotes undergo fermentation

31. This is called lactic acid fermentation. • Fermentation does NOT make energy • It changes the coenzyme NADH+H+ back to NAD+ for use in glycolysis

32. Prokaryotes do not have mitochondria or ANY membrane bound organelle. • They carry out respiration in the cytosol

33. Prokaryotes use the fermentation process to change the coenzyme NADH+H+ back to NAD+ • Microorganism fermentation produces ethyl alcohol and CO2

34. Glucose Catabolism Overview C6H12O6 6CO2(waste) + 12H2O + 36-38ATP(useful energy)

35. Summary:Carbohydrate Metabolic Reactions

36. Lipids Beta oxidation breaks down fatty acids to form acetyl Coenzyme A. Lipids are more reduced (have fewer oxygens); therefore, they have more potential chemical energy and can be more fully oxidized as an energy fuel. Therefore, we gain more energy, gram for gram, from fats than from carbohydrates.

37. Lipogenesis and Lipolysis Figure 24.14

38. Lipid Metabolism: Synthesis of Structural Materials • The liver: • Synthesizes lipoproteins for transport of cholesterol and fats • Makes tissue factor, a clotting factor • Synthesizes cholesterol for acetyl CoA • Uses cholesterol to form bile salts • Certain endocrine organs (ovaries, testes, and adrenal cortex) use cholesterol to synthesize steroid hormones

39. Protein Metabolism Amino acids may be deaminated and the resulting “carbon skeletons” of whatever composition, can be entered into the glycolytic or Krebs cycle pathways to yield an energy harvest of ATPS. The amino groups will be joined with CO2 molecules to form the nitrogenous waste urea.

40. Summary:Lipid and Protein Metabolic Reactions

41. Liver Metabolism • Hepatocytes carry out over 500 intricate metabolic functions • A brief summary of liver functions • Packages fatty acids to be stored and transported • Synthesizes plasma proteins • Forms nonessential amino acids • Converts ammonia from deamination to urea • Stores glucose as glycogen, and regulates blood glucose homeostasis • Stores vitamins, conserves iron, degrades hormones, and detoxifies substances

42. Cholesterol • Lipoproteins are classified as: • HDLs – high-density lipoproteins have more protein content • LDLs – low-density lipoproteins have a considerable cholesterol component • VLDLs – very low density lipoproteins are mostly triglycerides

43. Cholesterol

44. Plasma Cholesterol Levels • The liver produces cholesterol: • At a basal level of cholesterol regardless of dietary intake • Via a negative feedback loop involving serum cholesterol levels • In response to saturated fatty acids, increase cholesterol production in liver

45. Non-Dietary Factors Affecting Cholesterol • Stress, cigarette smoking, and coffee drinking increase LDL levels • Aerobic exercise increases HDL levels • Body shape is correlated with cholesterol levels • Fat carried on the upper body is correlated with high cholesterol levels • Fat carried on the hips and thighs is correlated with lower levels

46. The Daily Metabolic Cycle • The body shifts back and forth physiologically between the absorptive state and the postabsorptive state. • The absorptive state occurs for approximately 4 hours after each regular meal. • The postabsorptive state takes over until the next meal can be absorbed.

47. Regulation of Food Intake • Weight management • If energy consumption (food intake) equals energy utilized (activity), then body weight will remain constant • Activity and consumption levels vary day to day, but individuals keep relatively constant weight for long periods of time • Many individuals in affluent nations have an imbalance between intake and use  obesity

48. Regulation of Food Intake • Hypothalamus - complex integrating center receiving sensory information from all parts of the body • The arcuate nucleus contains several peptides that influence feeding • Neuropeptide Y (NPY)/ Agouti-related peptide (AgRP) stimulate feeding • Pro-opiomelanocortin (POMC)/ cocaine- and amphetamine-regulated transcript (CART) inhibit feeding

49. Regulation of Food Intake (cont.) • The hypothalamus has several inputs • Vagal inputs from the gut • Distenstion • Nutrients • Blood glucose • Blood amino acids • Blood fatty acids • Hormones • Insulin, CCK • Leptin – secreted by adipose cells • Glucagon, epinephrine • Ghrelin – secreted by stomach • Temperature - high temp decreases appetite • Social and psychological factors

50. Thermogenesis