Question

Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that breaks down glycogen, as depicted in Figure Q16-29. Referring to Figure Q16-29, 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 glucose available.
(d) A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

Answer 1

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

Step-by-step explanation:

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

When adrenaline activates PKA, it phosphorylates glycogen phosphorylase and activates glycogen breakdown. This leads to an increase in the amount of glucose available for immediate use in skeletal muscle cells. As a result, there will be less glycogen available in the cells since it is being broken down and converted to glucose.

On the other hand, a constitutively active mutant form of PKA in skeletal muscle cells would continuously activate glycogen phosphorylase, resulting in increased glycogen breakdown and a decrease in the amount of glycogen available. Therefore, statement (d) is false.