Question

The process of conversion of glycogen to glucose-6-phosphate is known as

• A. Glycolysis
• B. Glyconeogenesis
• C. Glycogenesis
• D. Glycogenolysis

Hint:

Suffix meanings:
-genesis = creation (glycogenesis)
-lysis = breakdown/destruction (glycogenolysis)
neo-genesis = new creation from non-carbohydrates (gluconeogenesis)

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Glycogen is a highly branched polymer of glucose that serves as the primary storage form of glucose in animals, stored mainly in skeletal muscle and liver tissue.
During periods of fasting or increased energy expenditure, glycogen must be mobilized to yield usable glucose units.

Step 2: Detailed Explanation:
The enzymatic breakdown of glycogen is called glycogenolysis.
This pathway involves three key steps:
Phosphorolysis of glycogen: The enzyme glycogen phosphorylase cleaves $\alpha(1\rightarrow4)$ glycosidic linkages from the non-reducing ends of the glycogen chain. It uses inorganic phosphate ($\text{P}_i$) to release glucose-1-phosphate.
Debranching: A specialized debranching enzyme resolves the $\alpha(1\rightarrow6)$ linkages at branch points, releasing a small amount of free glucose.
Isomerization: The enzyme phosphoglucomutase converts the released glucose-1-phosphate into glucose-6-phosphate.
In muscle tissue, this glucose-6-phosphate enters the glycolytic pathway directly to produce ATP for muscle contraction.
In liver tissue, glucose-6-phosphate can be dephosphorylated by glucose-6-phosphatase to release free glucose into the bloodstream, maintaining systemic blood glucose homeostasis.
Therefore, the specific series of reactions that degrade glycogen to glucose-6-phosphate represents the pathway of glycogenolysis.

Step 3: Final Answer:
The conversion of glycogen to glucose-6-phosphate is known as Glycogenolysis.