Glucose 1-phosphate ---------------> UDP-glucose (activated form of glucose)
Glycogen synthase cannot initiate glycogen synthesis; requires pre-existing primer of glycogen consisting of 4-8 glucose residues with ? (1,4) linkage.
Protein called glycogenin serves as anchor; also adds 7-8 glucose residues.
Addition of branches by branching enzyme (amylo-(1,4 --> 1,6)-transglycosylase).
Takes terminal 6 glucose residues from non-reducing end and attaches it via ? (1,6) linkage at least 4 glucose units away from nearest branch.