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Flashcards in Glycogen Regulation Deck (12):

A fasting man needs to break down glycogen; cAMP levels rise in liver cells to signal this. How does cAMP act to induce more glycogenolysis?

cAMP induces protein kinase A, which induces glycogen phosphorylase kinase, which induces glycogen phosphorylase to promote glycogenolysis


Calcium and the calcium-calmodulin complex both stimulate the conversion of glycogen to glucose. Biochemically, how does this occur?

Both induce glycogen phosphorylase kinase, which in turn activates glycogen phosphorylase to break down more glycogen into glucose


Via what 2 pathways does an activated insulin receptor trigger glycogenesis?

Direct glycogen synthase stimulation and indirect stimulation via protein phosphatase activation


Glycogen is made from glucose by what enzyme?

Glycogen synthase


Glucose is made from glycogen by what enzyme?

Glycogen phosphorylase via phosphorylation by glycogen phosph activation from PKA


Glucagon stimulates the breakdown of glycogen. In what organ/tissue does it exert its effects? How?

It acts via a cAMP 2nd-messenger system (creates cAMP from ATP via adenylate cyclase)


What 2 factors in muscle, by activating glycogen phosphorylase kinase, ensure that glycogenolysis is coordinated w/muscle activity?

Calcium and calmodulin


Epinephrine can encourage glycogen breakdown by way of 2 pathways. What are they?

Via α-receptors (which stimulate ER release of calcium) or β-receptors (which act via the cAMP 2nd-messenger system)


A pt under stress releases epinephrine, which binds to α-receptors. How does this help muscles contract more effectively?

Calcium exits the ER, inducing glycogen phosphorylase kinase (for glucose) and calcium-calmodulin (helps w/contractions)


Name the 3 activators of the enzyme glycogen phosphorylase kinase.

Calcium from epinephrine activation of alpha receptos in the liver, calcium-calmodulin complex via beta receptors that activate adenylate cyclase to increase cAMP and activate pKA, and protein kinase A via glucagon receptor in liver


What receptor does insulin bind to in liver and muscle cells? Which 2 enzymes does insulin directly stimulate to promote glycogen synthesis?

Tyrosine kinase dimer receptor
Insulin directly stimulates glycogen synthase and protein phosphatase


A man receives an α-blocker and epinephrine. Glycogen breakdown ↑ significantly, but muscle contractility only ↑ mildly. Why?

α-Receptor binding (blocked) promotes both muscle contraction and glycogenolysis; β-receptor binding (open) promotes glycogenolysis