Biochemistry : Glycogenolysis Regulation
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Example Questions
Example Question #1 : Alternative Pathways
Phosphorylation of glycogen phosphorylase has what effect on the enzyme?
Inactivation, conversion from glycogen phosphorylase B to glycogen phosphorylase A
Activation, conversion from glycogen phosphorylase B to glycogen phosphorylase A
Activation, conversion from glycogen phosphorylase A to glycogen phosphorylase B
Phosphorylation only confers partial activation
Phosphorylation has no effect
Activation, conversion from glycogen phosphorylase B to glycogen phosphorylase A
Phosphorylation of glycogen phosphorylase activates it, converting it from its inactive B-form to its active A-form.
Example Question #1 : Glycogenolysis Regulation
The process of glycogenolysis is an example of __________.
Phosphorolysis
Thiolysis
Hydrolysis
Lysis
Phosphorylation
Phosphorolysis
Phosphorolysis is the name given to the addition of phosphate across a bond. Remember that in glycogenolysis, glycogen phosphorylase adds a phosphate across the a-1,4-glycosidic bonds between the glucose units of glycogen. The result is that glucose leaves as glucose-1-phosphate. If hydrolysis were performed instead of phosphorolysis, free glucose would be severed from glycogen and would be able to leave the cell.
Example Question #3 : Glycogenolysis
Which of the following statements about glycogen phosphorylase (GP) is incorrect?
AMP is an inhibitor of glycogen phosphorylase.
This enzyme is active during times of starvation.
Glucose-6-phosphate is a negative regulator of glycogen phosphorylase.
The dephosphorylated form of glycogen phosphorylase is less active.
Glucose is a competitive inhibitor of glycogen phosphorylase.
AMP is an inhibitor of glycogen phosphorylase.
AMP is an activator of GP, whereas ATP is an inhibitor of GP. GP cleaves the alpha 1-4 glycosidic bond between a terminal glucose molecule and the rest of the glycogen straight chain, yielding glucose-1-phosphate during glycogenolysis.
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