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Questions 43 - 47

Questions 43 - 47. Starvation. 43. Liver Glycogenolysis. Which step is NOT INVOLVED the mobilization of liver glycogen? An increase in the activity of glycogen phosphorylase The activation of adenylyl cyclase An increase in intracellular cyclic-AMP (cAMP) concentration

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Questions 43 - 47

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  1. Questions 43 - 47 Starvation

  2. 43. Liver Glycogenolysis • Which step is NOT INVOLVED the mobilization of liver glycogen? • An increase in the activity of glycogen phosphorylase • The activation of adenylyl cyclase • An increase in intracellular cyclic-AMP (cAMP) concentration • Phosphorylation of protein kinase A • Phosphorylation of glycogen phosphorylase 27 30 10 113 30 fundamental to glycogenolysis the first step in making cAMP cAMP stimulates protein kinase A activated allosterically by cAMP the major way in which phosphoryase is activated

  3. 44. Muscle Glycogenolysis • Why doesn’t muscle glycogen contribute significantly to blood glucose homeostasis during starvation? • Because muscle does not express glucose 6-phosphatase • Because muscle does not express phosphorylase • Because muscle does not store enough glycogen • Because muscle has non-branched glycogen • Because muscle has a glycogen synthase that is insensitive to G6P lack of G6Pase makes it hard to release glucose 176 15 16 3 10 muscle phosphorylase is important in exercise muscle stores more than liver (in total) liver and muscle glycogen are structurally similar GS can respond to G6P in both liver and muscle – but this is irrelevant to release of glucose

  4. 45. Lipolysis in Starvation • What would be the consequences of inhibition of lipolysis during the first few days of starvation? • Blood ketone body concentration would rise • Blood glucose concentration would rise • Blood fatty acid concentration would rise • There would be fewer substrates for gluconeogenesis in the liver • Fatty acid oxidation in the muscles would increase need fatty acids to make ketone bodies 45 17 9 131 17 if alternate fuels not used, glucose will rapidly fall lipolysis releases fatty acids into the blood less glycerol, also less lactate (indirectly) FA oxidation rate proportional to blood [FA]

  5. 46. Regulation of PDH • What statement BEST DESCRIBES the regulation of muscle pyruvate dehydrogenase (PDH) during starvation • During the first three days of starvation, PDH is fully activated but it gets gradually switched off as starvation progresses • PDH becomes progressively more dephosphorylated during starvation • PDH kinase is activated during the first 48 h and stays active to the end • PDH phosphatase becomes progressively more active as starvation progresses • PDH becomes more active as starvation progresses need to switch PDH quicky …. and keep it off 45 26 111 21 10 dephosphorylation ACTIVATES PDH phosphorylation (and inactivation) is by PDH kinase need to keep PDH phosphatase inhibited need to keep PDH off

  6. 47. Ketone Bodies • Which statement about ketone bodies is INCORRECT? • Ketone bodies circulate in the blood stream bound to special carrier proteins • Ketone bodies can be used the peripheral tissues as well as the brain • Ketone bodies can spontaneously decarboxylate to give acetone • Ketone body oxidation requires a source of Coenzyme A • Ketone body oxidation will inhibit glucose oxidation freely soluble 107 24 22 32 32 used in any tissue with mitochondria acetoacetate to acetone happens a lot very similar to fatty acid oxidation – make acetyl CoA as with fatty acid oxidation – acetyl CoA inhibits PDH

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