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Regulation of Metabolism Lecture 28

Regulation of Metabolism Lecture 28. How does the body know when to increase metabolism? Slow metabolism? What might be some indicators of energy status within the cell?. Requires communication. Works through allosteric regulation of enzyme activity. Mechanisms of Cellular Communication.

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Regulation of Metabolism Lecture 28

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  1. Regulation of MetabolismLecture 28 • How does the body know when to increase metabolism? Slow metabolism? • What might be some indicators of energy status within the cell? Requires communication Works through allosteric regulation of enzyme activity

  2. Mechanisms of Cellular Communication Figure 6-1 - Overview

  3. What Hormones Regulate Metabolism? • Insulin • Glucagon • Thyroid hormone • Cortisol • Epinephrine Most regulation occurs in order to maintain stable blood glucose concentrations for supplying fuel to the brain!

  4. Protein or peptide hormone Almost always proteins called kinases Activation/inactivation of an enzyme; opening/closing a membrane channel; activating a transcription factor Figure 6-3

  5. Pancreas one islet of Langerhans Digestive enzymes and NaHCO3 hormones

  6. Anabolic hormone fatty acid & amino acid uptake  Glycolysis  Glycogen synth.  Lipogenesis  Protein synth. Plasma fatty acids, ketoacids & amino acids

  7. Catabolic hormone

  8. Mechanism of Insulin Action

  9. Major Effects of Insulin • Skeletal muscle takes up glucose from blood • Liver takes up glucose, increases glycogen production • Liver increases fatty acid synthesis when its glycogen stores are full • Adipose takes up blood glucose and fatty acid breakdown is inhibited Overall insulin has a fat sparing action. It works to store excess energy

  10. Mechanism of action for glucagon Glucagon from a cells of pancreas Figure 6-11 - Overview

  11. Effects of Glucagon and Insulin on Glucose Metabolism

  12. PFK-2 The allosteric regulator fructose-2,6-bisphosphate is synthesized & degraded by a bi-functional enzyme that includes 2 catalytic domains: Phosphofructokinase-2 (PFK2) domain catalyzes: Fructose-6-phosphate + ATP  fructose-2,6-bisphosphate + ADP Fructose-Biophosphatase-2 (FBPase2) domain catalyzes: Fructose-2,6-bisphosphate + H2O  fructose-6-phosphate + Pi Bifunctional PFK2/FBPase2 assembles into a homodimer.

  13. Fructose-2,6-bisphosphate

  14. ADP ADP Syn b Phos a Pkinase Ptase Ptase Syn a ATP Phos b ATP PO4 PO4 cAMP ATP cAMP as a Regulator of Glycogen Metabolism Pkinase Protein Kinase targets of cAPK cAMP Protein kinase (cAPK) Adenyl cyclase Glucagon Epinephrine

  15. Insulin

  16. Cortisol: slow catabolic effects; response to long-term stress increases protein breakdown in muscles and fat breakdown in adipose tissue, elevating amino acids and fatty acids in blood. increases glycogenolysis and gluconeogenesis in liver; elevates blood glucose synergistic effect for actions of glucagon and epinephrine in elevating blood glucose anti-inflammatory: inhibits cytokine activation of immune system Long-term excessive cortisol levels can cause severe muscle breakdown, lipolysis, and hyperglycemia. Hypersecretion may be from a tumor (Cushing's disease) or excess ACTH.

  17. Test Your Knowledge • The major hormones that promote glucose release into the blood are: • The major hormones that promote storage of glucose are: • A hepatic cell has receptors for epinephrine, glucagon, and insulin. These hormones may or may not act in concert to produce a desired effect. How does the hepatocyte know what to do? • What are the major second messenger systems used by the hormones that regulate blood glucose? What is the end result of activation of these second messenger systems?

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