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Chapter 22a Metabolism and Energy Balance. About this Chapter Appetite and satiety Energy balance Metabolism Homeostatic control of metabolism Regulation.

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Presentation on theme: "Chapter 22a Metabolism and Energy Balance. About this Chapter Appetite and satiety Energy balance Metabolism Homeostatic control of metabolism Regulation."— Presentation transcript:

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 Glucostatic theory Theory proposes that blood glucose levels ultimately control the feeding and satiety centers Lipostatic theory Theory proposes that the level of body fat regulates the feeding and satiety centers Recent discovery of several peptides (especially leptin and neuropeptide Y) seems to support this theory

6 Figure 22-1 Peptides Regulate the Feeding Center

7 Table 22-1 Many Peptides Alter Food Intake

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 CO 2 to O 2 (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 1.Immediate use in energy production 2.Synthesis into needed macromolecules 3.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 Figure 22-2 CarbohydratesFats Free fatty acids + glycerol Fat stores Glucose Excess glucose Glycogen stores Amino acids Proteins DIET Lipogenesis Brain metabolism Range of normal plasma glucose Gluconeogenesis Body protein Glycogenolysis Glycogenesis Protein synthesis Metabolism in most tissues Free fatty acid pool Urine Excess nutrients Lipolysis Glucose pool Amino acid pool Lipogenesis

15 Figure 22-2 (1 of 4) Carbohydrates Fat stores Glucose Excess glucose Glycogen stores DIET Lipogenesis Brain metabolism Range of normal plasma glucose Glycogenolysis Glycogenesis Metabolism in most tissues Urine Glucose pool Glucose Metabolism Most plasma glucose is used for immediate energy production, or is stored as glycogen

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

17 Amino acids Proteins DIET Range of normal plasma glucose Gluconeogenesis Body protein Protein synthesis Glucose pool Amino acid pool Figure 22-2 (3 of 4) Amino Acid Metabolism Amino acids are used for building needed body proteins. Excess amino acids are converted into glucose by the liver.

18 Summary of Metabolism Figure 22-2 (4 of 4) CarbohydratesFats Free fatty acids + glycerol Fat stores Glucose Excess glucose Glycogen stores Amino acids Proteins DIET Lipogenesis Brain metabolism Range of normal plasma glucose Gluconeogenesis Body protein Glycogenolysis Glycogenesis Protein synthesis Metabolism in most tissues Free fatty acid pool Urine Excess nutrients Lipolysis Glucose pool Amino acid pool Lipogenesis

19 Biochemical Pathways for Energy Production Overview of Pathways Figure 22-3 Glucose Some amino acids Lactate Glycogen Glucose 6-phosphate Liver only Fatty acids Electron transport system CO 2 NH 3 + H 2 OO2O CoA Ketone bodies (in liver) Glycerol 2 ATP Pyruvate Acetyl CoA NH 3 Cytoplasm Mitochondria Citric acid cycle ATP 2

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

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

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

23 Anaerobic Metabolism Produces Lactate Figure 22-3 (4 of 7) Glucose Some amino acids Lactate Glycogen Glucose 6-phosphate Liver only Glycerol Pyruvate NH 3 Cytoplasm Mitochondria ATP 2

24 Mitochondria and the Citric Acid Cycle Figure 22-3 (5 of 7) Glucose Some amino acids Lactate Glycogen Glucose 6-phosphate Liver only CO 2 CoA Glycerol 2 Pyruvate Acetyl CoA NH 3 Cytoplasm Mitochondria Citric acid cycle ATP 2

25 Fatty Acids and Some Amino Acids Enter Here Figure 22-3 (6 of 7) Glucose Some amino acids Lactate Glycogen Glucose 6-phosphate Liver only Fatty acids CO 2 NH 3 CoA Ketone bodies (in liver) Glycerol 2 Pyruvate Acetyl CoA NH 3 Cytoplasm Mitochondria Citric acid cycle ATP 2

26 Electron Transport System Figure 22-3 (7 of 7) Glucose Some amino acids Lactate Glycogen Glucose 6-phosphate Liver only Fatty acids Electron transport system CO 2 NH 3 + H 2 OO2O CoA Ketone bodies (in liver) Glycerol 2 ATP Pyruvate Acetyl CoA NH 3 Cytoplasm Mitochondria Citric acid cycle ATP 2

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 Figure 22-5 Dietary fats apo Chylomicron Monoglycerides Phospholipids Free fatty acids (FFA) Cholesterol FFA CM CM remnants Lymph Bile duct Blood Adipose cells Most cells Liver Intestinal lumen Intestinal cells lpl Glycerol HDL-CLDL-C Cholesterol + FFA + Lipoproteins Lipoprotein complexes Bile salts Metabolized Reassemble to triglycerides (TG) TG storage Lipolysis by lipases FFA oxidized for energy Cholesterol for synthesis KEY apo=apoproteins lpl=lipoprotein lipase LDL=low-density lipoprotein HDL = high-density lipoprotein C=cholesterol

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 Figure 22-7 Liver glycogen stores Energy production Free fatty acids Glycerol Amino acids Ketone bodies Glucose Adipose lipids become free fatty acids and glycerol that enter blood. Muscle glycogen can be used for energy. Muscles also use fatty acids and break down their proteins to amino acids that enter the blood. Liver glycogen becomes glucose. Brain can use only glucose and ketones for energy. or Triglyceride stores Glycogen Pyruvate Lactate Energy production Glucose Proteins Ketone bodies -oxidation Glycogenolysis Gluconeogenesis

32 Fasted-State Metabolism Figure 22-7 (1 of 4) Liver glycogen stores Free fatty acids Ketone bodies Glucose 1 Energy production Liver glycogen becomes glucose. -oxidation Glycogenolysis

33 Fasted-State Metabolism Figure 22-7 (2 of 4) Liver glycogen stores Free fatty acids Glycerol Ketone bodies Glucose Adipose lipids become free fatty acids and glycerol that enter blood. Triglyceride stores Gluconeogenesis 12 Energy production Liver glycogen becomes glucose. -oxidation Glycogenolysis

34 Fasted-State Metabolism Figure 22-7 (3 of 4) Liver glycogen stores Free fatty acids Glycerol Amino acids Ketone bodies Glucose Adipose lipids become free fatty acids and glycerol that enter blood. Muscle glycogen can be used for energy. Muscles also use fatty acids and break down their proteins to amino acids that enter the blood. or Triglyceride stores Glycogen Pyruvate Lactate Energy production Proteins Gluconeogenesis 12 3 Energy production Liver glycogen becomes glucose. -oxidation Glycogenolysis

35 Fasted-State Metabolism Figure 22-7 (4 of 4) Liver glycogen stores Energy production Free fatty acids Glycerol Amino acids Ketone bodies Glucose Adipose lipids become free fatty acids and glycerol that enter blood. Muscle glycogen can be used for energy. Muscles also use fatty acids and break down their proteins to amino acids that enter the blood. Brain can use only glucose and ketones for energy. or Triglyceride stores Glycogen Pyruvate Lactate Energy production Glucose Proteins Ketone bodies Gluconeogenesis Energy production Liver glycogen becomes glucose. -oxidation Glycogenolysis


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