Polysaccharide storage — What is the primary glucose storage polymer synthesized by animals?

Introduction:
Different kingdoms store glucose in distinct polysaccharides. This question asks you to identify the branched polymer used by animals as their major carbohydrate reserve, particularly in liver and skeletal muscle.

Given Data / Assumptions:

• Storage polymers must be mobilized rapidly when energy is needed.
• Branching degree influences solubility and accessibility to enzymes.
• Animal tissues maintain glucose homeostasis via storage and release.

Concept / Approach:
Glycogen is a highly branched α-1,4-linked glucose polymer with α-1,6 branch points roughly every 8–12 residues. Branching creates many non-reducing ends for rapid glycogen phosphorylase attack, enabling swift glucose mobilization. Liver glycogen buffers blood glucose; muscle glycogen fuels contraction locally.

Step-by-Step Solution:

Verification / Alternative check:
Histological PAS staining highlights glycogen granules in hepatocytes and myocytes; glycogen storage diseases demonstrate the metabolic centrality of glycogen synthesis and breakdown enzymes.

Why Other Options Are Wrong:

• Amylopectin: plant starch component, less highly branched than glycogen.
• Cellulose: structural β-1,4 polymer in plants; indigestible by humans.
• Collagen: a protein, not a carbohydrate polymer.
• Chitin: structural β-1,4 N-acetylglucosamine polymer in fungi/arthropods.

Common Pitfalls:
Confusing glycogen with starch; both are α-linked glucose polymers, but origin and branching frequency differ.

Final Answer:
Glycogen.