Uridine Diphosphate Glucose (UDP-glucose)

UDP-glucose is the activated form of glucose used in Glycogen synthesis as a glucose donor. The reaction of glucose 1-phosphate and uridine triphosphate (UTP), catalysed by UDP-glucose pyrophosphorylase, forms UDP-glucose by the removal of two phorphoryl groups from the UTP . Glucose 1-phosphate + UTP + H₂0 --------> UDP-glucose + 2P_i 

Glycogen synthase catalyses the formation of glycogen by adding the activated glucosyl unit from the UDP-glucose to the hydroxyl group on the carbon-4 atom of the glycogen molecule. 

Glycogen synthesis reaction: Glycogen_n + UDP-glucose ----> glycogen_n+1 + UDP