Carbohydrate Metabolism: Glycogenesis

Question 1

What is the active primer for glycogenesis?

Answer 1

glycogenin

Question 2

Which end does glucose molecules add onto during glycogenesis?

Answer 2

NON-REDUCING END

Question 3

Where and how is glycogen stored?

Answer 3

Glycogen is stored in muscle and liver cells.

Glycogen is stored as granules.

Question 4

What is the difference in the functionality between liver glycogen and muscle glycogen?

Answer 4

Liver glycogen is used for blood sugar maintenance.

Muscle glycogen is used as storage for energy for muscle cells.

Question 5

What are the different enzymes of glycogenesis and their roles in glycogen production?

Answer 5

Hexokinase/glucokinase- these enzymes trap glucose in the cytosol

Phosphoglucomutase- converts G6P –> G1P

UDP Glucose Pyrophosphorylase- transfers the G-1-P to UTP to produce UDP-Glucose and releases PPi

***Glycogen Synthase- is the rate limiting step of glycogenesis. Glycogen synthase adds UDP-Glucose to expanding Glycogen change on the NON-REDUCING END.

Question 6

What is the rate limiting step in glycogenesis?

Answer 6

The rate limiting step in glycogenesis is the addition of UDP-Glucose to glycogen on the non-reducing end by GLYCOGEN SYNTHASE.

Question 7

How does debranching of glycogen occur? What ENZYME?

Answer 7

Glucosyl 4:6 transferase does the debranching.

The way Glycosyl 4:6 transferase debranches is through the lysing of the glycogen polymer at 11 residues to about 7 resides and 4 residues. The 7 residues is added back at a branching site at an alpha-1,6- branching site.