Question 8: Insulin action in (skeletal) muscle.

[Anonymous]

Question 8: Insulin action in (skeletal) muscle.
Insulin regulates all of the following enzymes in liver. Which of these enzymes are also regulated by insulin in muscle?


[check all that apply]
Glycogen synthase
Glycogen phosphorylase
phosphofructokinase-1 (PFK-1)
phosphofructokinase-2 (PFK-2)
glucokinase



This is essentially the same figure as for insulin action in liver (question 1 of this module), and the five enzymes in question are denoted with question marks. The key for arriving at the correct answer is to determine which enzymes are missing in muscle...



Insulin action in muscle (not liver!)


ans:
Glycogen synthase

Glycogen phosphorylase

This sounds like a hard question, but it should not be. Recall that glucokinase and PFK-2 are liver specialties. Since PFK-1 is regulated indirectly via PFK-2, that also eliminates PFK-1. The only ones left are two enzymes controlling glycogen metabolism.