University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

85

Pages:

6
Author:

Sheha A.

**Glycogenesis** * Glycogen is an animal storage polysaccharide. * It is synthesized during the fed condition (energy-rich) and broken down during the fasting condition. **Definition:** Formation of glycogen from glucose is called glycogenesis. **Site:** * Tissue site: Liver and Muscle * Intracellular site: Cytosol **Starting Compound: Glucose** **End Product: Glycogen** **Reaction Pathway:** It takes place in 2 phases: a) Activation of Glucose b) Formation of Glycogen **A) Activation of Glucose:** Glucose + ATP → Glucose-6-phosphate + ADP Glucose-6-phosphate ⇌ Glucose-1-phosphate Glucose-1-phosphate + UTP → UDP-glucose + PPi **UDP glucose is the donor of glucose in glycogen synthesis.** **b) Lengthening of chain & formation of glycogen** It requires two enzymes: 1. Glycogen synthase 2. Branching enzyme **1) Glycogen Synthase** * By the action of glycogen synthase, UDP glucose donates its glucose into a pre-existing glycogen primer and lengthens the glycogen chains in a (1->4) direction to form glycogen polymers and liberating free UDP. **2) Branching Enzyme** * When the chain has been lengthened to a minimum of 11 glucose residues, a second enzyme, the branching enzyme, transfers a part of a (1->4) chain to a neighboring chain, producing a α (1->6) linkage, thus forming a new branching point. * Thus, a branching grows by further addition of glucose in a (1->4) by glycogen synthase and then further branching by branching enzyme.