Question

Which of the following types of regulation is considered the major way liver cells activate glycogen phosphorylase?

A) Transcriptional control
B) Post-translational modification
C) Allosteric regulation
D) Feedback inhibition

Answer 1

Allosteric regulation is the primary mechanism by which liver cells activate glycogen phosphorylase, where effector molecules bind to the enzyme and alter its activity to meet the energy demands of the cell. Option C.

Step-by-step explanation:

The major way that liver cells activate glycogen phosphorylase is through allosteric regulation. Glycogen phosphorylase is an enzyme that breaks down glycogen into glucose-1-phosphate molecules, which can then be utilized by the cell for energy during periods where glucose levels are low.

Allosteric regulation involves the binding of an allosteric effector to a site on the enzyme that is separate from the active site. This binding causes a conformational change that can either increase (activation) or decrease (inhibition) the enzyme's activity.

In the case of glycogen phosphorylase, allosteric effectors such as AMP can bind to the enzyme and change its conformation, thereby activating metabolism of glycogen.

While other forms of regulation exist, such as post-translational modification (which also plays a role in the activation of glycogen phosphorylase via phosphorylation), feedback inhibition, and transcriptional control, allosteric regulation is the primary control mechanism for this enzyme in liver cells. Option C.