Question

Glycogen synthesis and breakdown are regulated primarily at the hormonal level. however, important nonhormonal mechanisms also control the rates of synthesis and mobilization. part a describe these nonhormonal regulatory processes.

Answer 1

Glycogen metabolism is hormonal and allosteric regulated.

The allosteric regulation includes regulation (inhibition or activation) of an enzyme by a small regulatory molecule (effectors) which binds to the allosteric site (different than activation site).

Glycogen metabolism is allosterically controlled by glucose-6-phosphate, ATP and AMP.

 Glycogen phosphorylase is the main enzyme in degradation of glycogen and is regulated by several allosteric effectors that signal the energy state of the cell. When ATP is low and AMP high (cell needs energy) the phosphorylase needs to be activated in order to release glucose (energy source) from the store. On the other hand, glucose-6-phosphate will be plentiful when there is a lot of glucose and therefore signals an inhibition of glycogen degradation.

Glycogen synthase is the main enzyme for the synthesis of glycogen which is activated when there is plenty of glucose-6-phosphate.