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Chapter 22a

Chapter 22a. Metabolism and Energy Balance. About this Chapter. Appetite and satiety Energy balance Metabolism Homeostatic control of metabolism Regulation of body temperature. Appetite and Satiety. Food intake is carefully controlled Two competing behavioral states

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Chapter 22a

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  1. Chapter 22a Metabolism and Energy Balance

  2. About this Chapter • Appetite and satiety • Energy balance • Metabolism • Homeostatic control of metabolism • Regulation of body temperature

  3. Appetite and Satiety • Food intake is carefully controlled • Two competing behavioral states • Appetite (or hunger) = desire for food • Satiety = sense of fullness (or satisfaction) • Hypothalamus contains two key control centers • Feeding center • Satiety center

  4. Four Types of Input to the Hypothalamus • Neural input from the cerebral cortex • Neural input from the limbic system • Peptide hormones from the GI tract • Adipocytokines from adipose tissue

  5. Two Theories for Regulation of Food Intake • Glucostatictheory • Theory proposes that blood glucose levels ultimately control the feeding and satiety centers • Lipostatictheory • Theory proposes that the level of body fat regulates the feeding and satiety centers • Recent discovery of several peptides (especially leptinand neuropeptide Y) seems to support this theory

  6. Peptides Regulate the Feeding Center Figure 22-1

  7. Many Peptides Alter Food Intake Table 22-1

  8. Energy Balance - The Key to Weight Control • Energy input = energy output • Energy output = work  heat • Three categories of work done by our cells • Membrane transport • Mechanical work • Chemical work = building molecules, including synthesis of energy storage molecules • Short-term energy storage (ATP) • Long-term energy storage (glycogen, fat)

  9. Energy Balance • Methods for measuring energy use • Direct calorimetry • Measures the energy content of food • Fat 9 Kcal/g / protein and CHO ~ 4 Kcal/g • Indirect calorimetry • Estimates metabolic rate as a measure of energy use • Oxygen consumption • Carbon dioxide production • Ratio of CO2 to O2 (RQ or RER)

  10. Metabolic Rate • Basal metabolic rate (BMR) is most common measure of metabolic rate • Six factors affecting metabolic rate 1 - Age and gender 2 - Amount of lean muscle mass 3 - Activity level 4 - Energy intake (diet) – fat vs protein thermogenesis 5 – Hormones – thyroid hormone thyroxin 6 - Genetics • Only energy intake and level of physical activity can be voluntarily changed

  11. Two Chemical Forms of Energy Storage • Glycogen (highly branched polymer of glucose) • Stored glycogen binds water • Liver glycogen is used to regulate blood glucose • Muscle glycogen is used to power muscle contraction • Fat (triglycerides) • Fats have higher energy content per gram • Little water is required for fat storage • Energy in fats is harder and slower to access

  12. Metabolism • Metabolism is all of the chemical reactions in the body 1 - Extract energy from nutrients 2 - Use energy for work and synthesis 3 - Store excess energy • Two types of metabolic pathways • Anabolic pathways build large molecules • Catabolic pathways break down large molecules • Metabolism can be divided into two states • Absorptive (“fed”) state is anabolic • Post-absorptive (“fasted”) state is catabolic

  13. Metabolic Fates and Nutrient Pools • Ingested biomolecules have three fates • Immediate use in energy production • Synthesis into needed macromolecules • Storage for later use in energy production • Nutrient pools are available for immediate use • Free fatty acids • Plasma glucose pool • Amino acid pool Know definitions of: Glycogenesis/ glycogenolysis / lipogenesis / lipolysis / ketosis

  14. Overview of Metabolism DIET Fats Carbohydrates Proteins Free fatty acids + glycerol Proteinsynthesis Glycogenesis Aminoacids Glucose Fatstores Lipogenesis Excess glucose Lipogenesis Bodyprotein Glycogenstores Urine Lipolysis Glycogenolysis Glucose pool Gluconeogenesis Free fattyacid pool Range of normalplasma glucose Amino acidpool Metabolism inmost tissues Brainmetabolism Excess nutrients Figure 22-2

  15. Glucose Metabolism DIET • Most plasma glucose is used for immediate energy production, or is stored as glycogen Carbohydrates Glycogenesis Glucose Fatstores Lipogenesis Excess glucose Glycogenstores Urine Glycogenolysis Glucose pool Range of normalplasma glucose Metabolism inmost tissues Brainmetabolism Figure 22-2 (1 of 4)

  16. Fat Metabolism DIET • Free fatty acids are used for immediate energy production, or are stored as fat molecules in adipose tissue Fats Free fatty acids + glycerol Fatstores Lipogenesis Lipolysis Free fattyacid pool Metabolism inmost tissues Excess nutrients Figure 22-2 (2 of 4)

  17. Amino Acid Metabolism DIET • Amino acids are used for building needed body proteins. Excess amino acids are converted into glucose by the liver. Proteins Proteinsynthesis Aminoacids Bodyprotein Glucose pool Gluconeogenesis Range of normalplasma glucose Amino acidpool Figure 22-2 (3 of 4)

  18. Summary of Metabolism DIET Fats Carbohydrates Proteins Free fatty acids + glycerol Proteinsynthesis Glycogenesis Aminoacids Glucose Fatstores Lipogenesis Excess glucose Lipogenesis Bodyprotein Glycogenstores Urine Lipolysis Glycogenolysis Glucose pool Gluconeogenesis Free fattyacid pool Range of normalplasma glucose Amino acidpool Metabolism inmost tissues Brainmetabolism Excess nutrients Figure 22-2 (4 of 4)

  19. Biochemical Pathways for Energy Production • Overview of Pathways Glycogen Glucose 6-phosphate Glucose Liver only Glycerol ATP 2 NH3 Someaminoacids Lactate Pyruvate Cytoplasm Mitochondria Pyruvate Fatty acids Acetyl CoA CoA Ketone bodies (in liver) CO2 Citric acidcycle 2 ATP Electron transportsystem Someaminoacids NH3 ATP O2 26-28 + H2O Figure 22-3

  20. Interconversions of Glucose Glycogen Glucose 6-phosphate Glucose Liver only Cytoplasm Mitochondria Figure 22-3 (1 of 7)

  21. Glycolysis is Catabolism of Glucose Glycogen Glucose 6-phosphate Glucose Liver only ATP 2 Pyruvate Cytoplasm Mitochondria Figure 22-3 (2 of 7)

  22. Some Amino Acids Can Also Supply Pyruvate Glycogen Glucose 6-phosphate Glucose Liver only Glycerol ATP 2 NH3 Someaminoacids Pyruvate Cytoplasm Mitochondria Figure 22-3 (3 of 7)

  23. Anaerobic Metabolism Produces Lactate Glycogen Glucose 6-phosphate Glucose Liver only Glycerol ATP 2 NH3 Someaminoacids Lactate Pyruvate Cytoplasm Mitochondria Pyruvate Figure 22-3 (4 of 7)

  24. Mitochondria and the Citric Acid Cycle Glycogen Glucose 6-phosphate Glucose Liver only Glycerol ATP 2 NH3 Someaminoacids Lactate Pyruvate Cytoplasm Mitochondria Pyruvate Acetyl CoA CoA CO2 Citric acidcycle 2 ATP Figure 22-3 (5 of 7)

  25. Fatty Acids and Some Amino Acids Enter Here Glycogen Glucose 6-phosphate Glucose Liver only Glycerol ATP 2 NH3 Someaminoacids Lactate Pyruvate Cytoplasm Mitochondria Pyruvate Fatty acids Acetyl CoA CoA Ketone bodies (in liver) CO2 Citric acidcycle 2 ATP Someaminoacids NH3 Figure 22-3 (6 of 7)

  26. Electron Transport System Glycogen Glucose 6-phosphate Glucose Liver only Glycerol ATP 2 NH3 Someaminoacids Lactate Pyruvate Cytoplasm Mitochondria Pyruvate Fatty acids Acetyl CoA CoA Ketone bodies (in liver) CO2 Citric acidcycle 2 ATP Electron transportsystem Someaminoacids NH3 ATP O2 26-28 + H2O Figure 22-3 (7 of 7)

  27. Metabolism: Push-Pull Control • Metabolic balance can shift when enzyme activity is controlled Figure 22-4

  28. Metabolism: Fates of Nutrients in the Fed State Table 22-2

  29. Transport and Fate of Dietary Fats Dietaryfats Intestinallumen MonoglyceridesPhospholipidsFree fatty acids (FFA) Cholesterol apo Intestinalcells CM FFA Chylomicron Lymph Adipose cells Blood Bileduct Lipolysis by lipases CM lpl FFA Reassembleto triglycerides(TG) TGstorage Glycerol CMremnants Most cells HDL-C LDL-C FFA oxidizedfor energy Liver Cholesterolfor synthesis Metabolized Lipoproteincomplexes KEY apo=apoproteinslpl=lipoprotein lipaseLDL=low-density lipoproteinHDL = high-density lipoproteinC=cholesterol Cholesterol + FFA + Lipoproteins Bile salts Figure 22-5

  30. High LDL-C Levels Increase Heart Disease Risk • LDL-C takes cholesterol from liver to most cells • High LDL-C increases risk of atherosclerosis • Many drugs try to lower cholesterol levels by changing its metabolism • Low HDL is another risk factor for atheroslerosis Figure 22-6

  31. Fasted-State Metabolism 1 2 Liver glycogenbecomes glucose. Adipose lipidsbecome freefatty acids andglycerol thatenter blood. Triglyceride stores Free fattyacids Liverglycogenstores Free fattyacids Glycerol -oxidation Glycogenolysis Gluconeogenesis Energyproduction Ketonebodies Energy production Glucose Glycogen Proteins Gluconeogenesis Pyruvate or Lactate Aminoacids Ketonebodies Glucose Energy production 3 Muscle glycogen can be used for energy.Muscles also use fatty acids and breakdown their proteins to amino acids thatenter the blood. 4 Brain can useonly glucose andketones for energy. Figure 22-7

  32. Fasted-State Metabolism 1 Liver glycogenbecomes glucose. Liverglycogenstores Free fattyacids -oxidation Glycogenolysis Energyproduction Ketonebodies Glucose Figure 22-7 (1 of 4)

  33. Fasted-State Metabolism 1 2 Liver glycogenbecomes glucose. Adipose lipidsbecome freefatty acids andglycerol thatenter blood. Triglyceride stores Free fattyacids Liverglycogenstores Free fattyacids Glycerol -oxidation Glycogenolysis Gluconeogenesis Energyproduction Ketonebodies Glucose Figure 22-7 (2 of 4)

  34. Fasted-State Metabolism 1 2 Liver glycogenbecomes glucose. Adipose lipidsbecome freefatty acids andglycerol thatenter blood. Triglyceride stores Free fattyacids Liverglycogenstores Free fattyacids Glycerol -oxidation Glycogenolysis Gluconeogenesis Energyproduction Ketonebodies Energy production Glucose Glycogen Proteins Gluconeogenesis Pyruvate or Lactate Aminoacids 3 Muscle glycogen can be used for energy.Muscles also use fatty acids and breakdown their proteins to amino acids thatenter the blood. Figure 22-7 (3 of 4)

  35. Fasted-State Metabolism 1 2 Liver glycogenbecomes glucose. Adipose lipidsbecome freefatty acids andglycerol thatenter blood. Triglyceride stores Free fattyacids Liverglycogenstores Free fattyacids Glycerol -oxidation Glycogenolysis Gluconeogenesis Energyproduction Ketonebodies Energy production Glucose Glycogen Proteins Gluconeogenesis Pyruvate or Lactate Aminoacids Ketonebodies Glucose Energy production 3 Muscle glycogen can be used for energy.Muscles also use fatty acids and breakdown their proteins to amino acids thatenter the blood. 4 Brain can useonly glucose andketones for energy. Figure 22-7 (4 of 4)

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