Answer:
The correct statement regarding glycogen synthase is:
b) It catalyzes the addition of glucose residues to the non-reducing end of a glycogen chain by the formation of (a1->4) bonds.
Glycogen synthase is an enzyme involved in glycogen synthesis, which is the process of building glycogen, a storage form of glucose. It catalyzes the addition of glucose residues to the non-reducing end of a glycogen chain by forming (a1->4) glycosidic bonds. This elongates the glycogen chain.
Let's briefly review the other options as well:
a) Activation of the enzyme involves phosphorylation: This statement refers to glycogen synthase kinase (GSK-3), not glycogen synthase itself. GSK-3 phosphorylates and inhibits glycogen synthase.
c) It uses glucose-6-phosphate as a donor of glucose units: This statement refers to glycogenin, an enzyme involved in initiating glycogen synthesis. Glycogenin uses glucose-6-phosphate as a primer for glycogen synthesis, but glycogen synthase uses UDP-glucose as the glucose donor.
d) The concentration of cAMP controls the conversion of an active to an inactive form of the enzyme: This statement refers to the regulation of glycogen phosphorylase, not glycogen synthase. Glycogen phosphorylase is regulated by the concentration of cAMP, which controls its conversion between active (phosphorylated) and inactive (dephosphorylated) forms.
e) The enzyme has measurable activity only in the liver: This statement is incorrect. While glycogen synthase activity is prominent in the liver, it is also present in other tissues, including muscle and brain. Different isoforms of glycogen synthase are expressed in various tissues, allowing for the synthesis of glycogen in different organs.
Therefore, the correct statement is b) It catalyzes the addition of glucose residues to the non-reducing end of a glycogen chain by the formation of (a1->4) bonds.
Step-by-step explanation: