Question

1. ATP is needed to phosphorylate enzymes in the cascade pathway for glycogen phosphorylase. It also serves as an allosteric effector. A) Describe the effects of the cascade and the allosteric effects of ATP. B) If ATP levels are high, what is the most likely outcome for the activity of glycogen phosphorylase? Explain your reasoning.

Answer 1

Ans A:- glycogen phosphorylase is rate .limiting step in glycogenolysis which is breakdown of glycogen into glucose for energy production in the from of ATP. glycogen phosphorylase act on glycogen and catalyse hydrolysis of it in the presence of ATP which yield glucose 1-phosphate. glucose produced then undergo series of breakdown called glycolysis to for pyruvate. pyruvate then enter into creb's cycle to produce ATP. glycogen phosphorylase has two form a and b. ATP has negative allosteric effect on phosphorylase b which is when ATP and glucose is present in higher concentration, phosphorylase b will stay in inactive form and glycogenosis would not happen.

Ans B:- if ATP level is high glycogen phosphorylase will stop or not proceed futher breakdown of glycogen into glucose. as phosphorylase b has a negative allosteric effect high level of ATP suggest high energy present in cell and no need for more energy and signal accordingly. hence glycogen breakdown would not occur.