Synthesis of glycogen by the enzyme glycogen synthase requires an activated form of glucose that is synthesized by the condensation of glucose 1-phophate with

a) ATP

b) GTP

c) CTP

d) UTP

e) TTP

D. UTP

Explanation:

Glycogen synthase is the enzyme that catalyzes glycogen chain elongation by transferring a glucose residue from UDP-glucose to the non-reducing end of the existing branch of glycogen. The incoming glucose is bonded to the non-reducing end by alpha (1 to 4) glycosidic linkage.

For the purpose, glucose - 6 phosphate is converted into glucose - 1 phosphate. The enzyme UDP-glucose pyrophosphorylase then converts the glucose-1 phosphate into UDP-glucose by condensation of glucose-1 phosphate with UTP and pyrophosphate is released.

The UDP - glucose serves as an immediate donor of glucose residue for elongation of glycogen catalyzed by glycogen synthase. Conversion of glucose-6 phosphate into glucose - 1 phosphate and then into UDP-glucose favors the glycogen synthesis energetically.