Biochemistry : Glycogenolysis Regulation
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Example Questions
Example Question #1 : Glycogenolysis
Phosphorylation of glycogen phosphorylase has what effect on the enzyme?
Phosphorylation has no effect
Activation, conversion from glycogen phosphorylase B to glycogen phosphorylase A
Inactivation, conversion from glycogen phosphorylase B to glycogen phosphorylase A
Phosphorylation only confers partial activation
Activation, conversion from glycogen phosphorylase A to glycogen phosphorylase B
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 : Alternative Pathways
The process of glycogenolysis is an example of __________.
Phosphorolysis
Lysis
Thiolysis
Hydrolysis
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 #1 : Alternative Pathways
Which of the following statements about glycogen phosphorylase (GP) is incorrect?
Glucose is a competitive inhibitor of glycogen phosphorylase.
AMP is an inhibitor of glycogen phosphorylase.
Glucose-6-phosphate is a negative regulator of glycogen phosphorylase.
This enzyme is active during times of starvation.
The dephosphorylated form of glycogen phosphorylase is less active.
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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