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What Is Metabolism?

What Is Metabolism?. Catabolism Reactions that break down compounds into small units. What Is Metabolism?. Anabolism Reactions that build complex molecules from smaller ones. What Is Metabolism?. ATP is the body ’ s energy currency ATP = adenosine triphosphate.

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What Is Metabolism?

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  1. What Is Metabolism? Catabolism Reactions that break down compounds into small units

  2. What Is Metabolism? Anabolism Reactions that build complex molecules from smaller ones

  3. What Is Metabolism? ATP is the body’s energy currency ATP = adenosine triphosphate

  4. Breakdown and Release of Energy • Anaerobic • Partial breakdown glucose • Do not req oxygen • Lactic acid is main end-product little ATP • Aerobic • Complete breakdown glucose, fat, and protein • Occurs in mitochondria • Releases most energy • CO2 , H2O, ATP and heat • Req oxygen

  5. Breakdown and Release of Energy Extracting energy from carbs Glycolysis Splits glucose into two pyruvates Produces some ATP Pyruvate to acetyl CoA Releases CO2 Enters TCA cycle if O2 is present

  6. Breakdown and Release of Energy Lipolysis Triglycerides broken down into fatty acids and glycerol Extracting energy from fat Promoted by glucagon, growth hormone, epinephrine Takes place in mitochondria Beta-oxidation Breaks fatty acids into acetyl CoA Fat burns in a flame of carbohydrate Ketogenesis Ketone bodies formed by incomplete fatty acid oxidation

  7. Breakdown and Release of Energy Extracting energy from protein Split protein into amino acids Split off amino group Converted to urea for excretion Carbon skeleton enters breakdown pathways End products ATP, H2O, CO2, urea

  8. Protein Metabolism • Gluconeogenesis • Forming glucose from glucogenic amino acids and other compounds • Typical fatty acids cannot be converted to glucose, although glycerol can • Disposal of Excess Amino Groups • Converted to ammonia; then urea cycle • Urea excreted in the urine

  9. Breakdown and Release of Energy

  10. Biosynthesis and Storage Making carbs Gluconeogenesis Uses pyruvate, lactate, glycerol, certain AA Storing carbohydrate (glucose  glycogen) Liver and muscle make glycogen from glucose Making fat (fatty acids) Lipogenesis Uses acetyl CoA from fat, amino acids, and glucose Storing fat (triglyceride) Stored in adipose tissue

  11. Biosynthesis and Storage Making ketone bodies (ketogenesis) From acetyl CoA When inadequate glucose in cells Making protein (amino acids) Amino acid pool supplied from Diet, protein breakdown, and cell synthesis Biosynthesis Different pathways used to build amino acids from carbon skeletons

  12. Fasting and Feasting • Fasting encourages: • Glycogen breakdown • Body fat and protein breakdown • Gluconeogenesis • Ketogenesis • Urea synthesis • Feasting encourages: • Glycogen synthesis • Body fat synthesis (lipogenesis) • Protein synthesis

  13. Special States Feasting Excess energy intake from carbs, fat, protein Promotes storage Fat  adipose AA  protein synthesis Carbohydrate  adipose

  14. Special States Fasting Inadequate energy intake Promotes breakdown Prolonged fasting Protects body protein aslong as possible

  15. Special States • Fasting • Survival priorities and potential energy sources • Preserve glucose-dependent tissue • RBC, brain cells, central nervous system • Maintain muscle mass • The prolonged fast: In the beginning • Blood glucose drops, liver breaks down glycogen to glucose • Gluconeogenesis • Fat and protein are primary fuel

  16. Special States • Fasting • The early weeks • Several energy-conservation strategies • Several weeks of fasting • Rely on stored body fat • The end is near • Muscle atrophy and emaciation • Sacrificed muscle tissue in attempt to preserve brain tissue

  17. Weight Management • Adopting a healthy weight-management lifestyle • Diet and eating habits • Total calories • Crash diets don’t work • Balancing energy sources: fat, carbohydrate, and protein • Eating habits • Physical activity

  18. Thrifty Gene and weight lossWhat happens to metabolism when calorie intake is severely restricted?WHY?

  19. In general, when non-athletes loss wt:- loss 50 % adipose & 50% lean tissue- wt gain 75% adipose & 25% lean tissueOne definition of yo-yo dieting:restricted eating –loss 10 lbs or so, plateau (doesn’t seem to loss any more wt), gets frustrated – go off “diet” and regain the weight.

  20. Scenario: 1. Steve weights 200 lbs and wants to loss wt..Over the course of 6 months, he goes on 3 yo-yo diets. At the end of the 6 months he still weights 200 lbs– did anything change?Explain what happened to his body composition over the 6 months.

  21. 2. From the previous scenario, how could the amount of muscle mass lost be altered?

  22. This time Steve decides to exercise & restrict calories. Over the course of a month, Steve losses 10 lbs. but then plateaus out. What might be happening?

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