Glycogenesis

Question 1

What is the purpose of glycogenesis?

Answer 1

To synthesize glycogen from glucose for energy storage.

Glycogenesis takes place in the liver, muscles and kidneys

Cytosol of the cells

This is an anabolic reaction

Question 2

What is the 1st reaction of glycogenesis?

Answer 2

Glucose to Glucose-6-phosphate

Purpose: Traps glucose within the cell in an ATP-dependent manner

Enzyme: Transferase (Hexokinase and Glucokinase in the liver)

Biochemical process: Phosphorylation

Spontaneous and non-reversible

Question 3

What is the 2nd reaction of glycogenesis?

Answer 3

Glucose-6-phosphate to Glucose-1-phosphate

Purpose; Reshuffle the phosphate group

Enzyme: Isomerase (Phosphoglucomutase)

Biochemical process: Isomerization

Rxn is spontaneous and reversible

Question 4

What is the 3rd rxn of glycogenesis?

Answer 4

Glucose-1-phosphate to UDPG + PPi

Purpose: Convert to the activated form of glucose in UTP-dependent manner

Enzyme: Lyase (UDPG pyrophorylase)

Biochemical process: Phosphorolysis

Break down of inorganic phosphate pulls the reaction in one direction

Question 5

What is the “extra” step of glycogenesis?

Answer 5

PPi + H₂O to 2 Pi

Purpose: Rapidly break down PPi

Enzyme: Hydrolase (Pyrophosphatase)

Biochemical process: Hydrolysis and dephosphorylation

Spontaneous and irreversible

Question 6

What is the 4th step of glycogenesis?

Answer 6

Glycogen primer + UDPG to glycogen + UDP

Purpose: Donate glucose from UDPG to glycogen

Enzyme: Lyase (Glycogen synthtase)

Biochemical process: Synthesis (Glycogen synthase)

This reaction is spontaneous and irreversible