Editing Glycogen (section)

===Synthesis===
{{Main|Glycogenesis}}

Glycogen synthesis is, unlike its breakdown, [[endergonic]]—it requires the input of energy. Energy for glycogen synthesis comes from [[uridine triphosphate]] (UTP), which reacts with [[glucose-1-phosphate]], forming [[UDP-glucose]], in a reaction catalysed by [[UTP—glucose-1-phosphate uridylyltransferase]]. Glycogen is synthesized from monomers of [[UDP-glucose]] initially by the protein [[glycogenin]], which has two [[tyrosine]] anchors for the reducing end of glycogen, since glycogenin is a homodimer. After about eight glucose molecules have been added to a tyrosine residue, the enzyme [[glycogen synthase]] progressively lengthens the glycogen chain using UDP-glucose, adding α(1→4)-bonded glucose to the nonreducing end of the glycogen chain.<ref>{{cite book |last=Nelson |first=D. |year=2013 |title=Lehninger Principles of Biochemistry |edition=6th |page=618 |publisher=W.H. Freeman and Company}}</ref>

The [[glycogen branching enzyme]] catalyzes the transfer of a terminal fragment of six or seven glucose residues from a nonreducing end to the C-6&nbsp;hydroxyl group of a glucose residue deeper into the interior of the glycogen molecule. The branching enzyme can act upon only a branch having at least 11&nbsp;residues, and the enzyme may transfer to the same glucose chain or adjacent glucose chains.