A constant source of blood glucose is an absolute requirement for human life. That is why the body developed mechanisms for storing a supply of glucose in a rapidly mobilize herbal form namely glycogen these mechanisms are glycogenesis.
The conversion of glucose to glycogen for storage and glycogenolysis the conversion of glycogen back to glucose for utilization.
Let's first discuss glycogenesis which is composed of four steps
Glycogenesis Steps
Step 1: The Synthesis of Uridine di-phosphate glucose
It is synthesized from Glucose-1-phosphate & Uridine triphosphate, acted upon by the enzyme UDP glucose pyrophosphate, forming now your Uridine di-phosphate glucose.
Step 2: Synthesis of a Primer to initiate Glycogen synthesis
Since adding UDP glucose and other glucose molecules to elongate the chain via glycogen synthase cannot occur. A primer should be first formed. A protein called glycogen can serve as an acceptor of glucose residues from UDP glucose. Glycogen in itself can catalyze this reaction because it is an enzyme. Just add few more molecules of glucose from UDP glucose producing a short alpha 1-4 linked glucose cell chain that can serve as a primary that is able to be elongated by glycogen synthase.
Step 3: Elongation of Glycogen Chains
You can now add molecules of glucose from UDP glucose at the non-reducing end to elongate the chain via glycogen synthase. It is the enzyme responsible for making the alpha one four linkages in glycogen.
Step 4: Formation of Branches
The branches are made by the action of the enzyme Amylo alpha (1-4) to alpha (1-6) trans-glucosidase. It removes a set of 6 to 8 glucose residues from the non-reducing end of the glycogen chain, breaking an alpha 1-4 bond and attaches it to a non terminal glucose, will residual by an alpha 1-6 linkage. Resulting to a new non-reducing end.
You can now repeat step 3 and 4 to form a highly branched polysaccharide, named glycogen.