Question

Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that breaks down glycogen. Which of the following statements below is false?
a. A constitutively active mutant form of PKA in skeletal muscle cells would lead to a decrease in the amount of unphosphorylated phosphorylase kinase.
b. A constitutively active mutant form of PKA in skeletal muscle cells would not increase the affinity of adrenaline for the adrenergic receptor.
c. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.
d. A constitutively active mutant form of PKA in skeletal muscle cells would increase the amount of phosphorylated glycogen phosphorylase.
e. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glucose available.

Answer 1

Answer:

d) A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

Explanation:

This occurs in the process of Glycogenolysis. The process involves breaking down of glycogen to glucose  -1- phosphate and glycogen which helps in the release of glucose into the blood stream to prevent hypoglycemia(low blood sugar). The glucose-1-phosphate is later converted to glucose -6-phosphate. The latter enters the glycolytic pathway in which the reaction is catalysed by the enzyme phosphoglucomutase.

This homeostatic glucose regulation  is regulated by the protein kinase(PKA)/ cAMP pathway in the skeletal muscles, the liver and the pancreas.

Answer 2

Answer:

c. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

Explanation:

This represented the process of Glycogenlysis. The breaking down of glycogen to glucose  -1- phosphate  and glycogen  to release glucose into the blood stream to prevent hypoglycemia. The glucose-1-phosphate is later converted to glucose -6-phosphate. The latter enters the glycolytic parthway. The reaction is catalysed by the enzyme phosphoglucomutase.

This homeostatic glucose regulation   is regulated by the protein kinase(PKA)/ cAMP pathway in the skeletal muscles, the liver and the pancreas. The PKA/cAMP signaling  pathway, also regulate glucose uptake,  breakdown of glycogen, insulin and glucagon synthesis.