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

2024
Views:

156

Pages:

5
Author:

Sheha A.

Glycogenolysis It is the breakdown of glycogen. Glycogen is the storage form of glucose. It is stored mainly in the liver and muscle. Glycogenolysis involves two sequential steps: Phosphorolysis: Glycogen is broken down to glucose-1-phosphate. Isomerization: Glucose-1-phosphate is converted to glucose-6-phosphate. Phosphorolysis: Glycogen is broken down to glucose-1-phosphate. This is a combined action of 3 enzymes. Enzymes Involved: Glycogen phosphorylase Glycogen debranching enzyme Phosphoglucomutase It cleaves α-1,4-glycosidic bonds, releasing terminal glucose residues as glucose-1-phosphate. Glycogen phosphorylase continues until 4 glucose residues remain on each branch. Glycogenolysis 1) Glycogen Phosphorylase: It cleaves α-1,4 glycosidic bonds, releasing one glucose residue at a time as glucose 1-phosphate. Continues the process of glycogen breakdown to give glucose 1-phosphate and new free glucose molecules. Fate of Glucose 1-phosphate: a) In liver: Glucose 1-phosphate is converted to glucose 6-phosphate. b) In muscle: Muscle lacks glucose 6-phosphatase enzyme, so the end product is glucose 6-phosphate. Significance of Glycogenolysis: a) Hepatic Glycogenolysis: Takes place to maintain blood glucose levels during fasting. b) Muscle Glycogenolysis: Provides glucose for muscle contraction during intense exercise. Regulation of Glycogenolysis Glycogen phosphorylase is the key enzyme in glycogenolysis. It is regulated by covalent modification. The phosphorylated form of glycogen phosphorylase is active.