A linear homopolymer of glucose residues (long glucose chain) stored in body has 2 ends, reducing end (OH) = squiggle glycosidic bonds (covalent) alfa-(1,4)-glycosidic bonds: between glucose residues alfa-(1,6)-glycosidic bonds: branch points

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Structure of glycogen

3 important questions on Structure of glycogen

What is the structure of free glucose and with what can it react?

Glucose has an aldehyde group (reactive group, H-C (delta+) = O (delta-)) which can react with other molecules

Vitro: Fehlings reagent (Cu2+ ions)

Cu2+ to 2 Cu
aldehyde group is oxidized carboxyl group (H-C=O → OH-C=O)

Vivo: amino group of protein

glucose can attache to proteins in 2 ways

Glycosylation: glucose transfer via condensation reaction (enzymatic)
Glycation: spontanous irreversible transfer of glucose (non-enzamatic)

Intramolecular: The C5 hydroxyl group

glucose react with hydroxyl group at C5, forming a alfa-anomer (axial) or beta-anomer (equatorial)
possition of OH group changes

What is a glucan?

A linear homopolymer of glucose residues (long glucose chain) stored in body

has 2 ends, reducing end (OH) = squiggle
glycosidic bonds (covalent)

alfa-(1,4)-glycosidic bonds: between glucose residues
alfa-(1,6)-glycosidic bonds: branch points

What is proteo-glycogen? How is it formed?

Initiation

Glycogenin (GN) has a Tyr residue when a homodimer forms, it can auto-glycosylate and continues until 8 glucose are added

Elongation

Glycogen synthase (GS) extends existing chains

Branching

Branching enzyme (BE) removes an oligosaccharide of 7 glucose residues from the non reducing end that is minimally 11 glucose residues in length
transfers it to create a new branch point that is at least 4 glucose residues away from a preexisting branch point

The question on the page originate from the summary of the following study material:

Laura's Medical biochemistry and pathophysiology

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