Glycogen Metabolism

Question 1

What cells does glycogenesis and glycogenolysis occur in?

Answer 1

Liver and skeletal muscle cells

• cells that need to get energy fast if free glucose levels are low.

Question 2

Glucose is the primary energy source for what cells?

Answer 2

Nervous cells, erythrocytes, and white skeletal muscle cells

Question 3

Activation steps of glycogenesis

Answer 3

G6-P -> G1-P

• done via PGM

G1-P -> UDP glucose

• done via UDP-GPPase

Question 4

How is the chain of glycogen produced?

Answer 4

UDP-glucose activated C1 binds to C4 of a pre-exisiting glycogen chain.

• forms a (a) 1,4 bond

Question 5

Primary regulatory of glycogenesis

Answer 5

Glycogen synthase

• activated via insulin(hyperglycemia)
• inhibited by glucagon (hypoglycemia)

Question 6

Enzyme that cleaves (a) 1,4 bonds in glycogen

Answer 6

Phosphorylase

• works on ONLY (a) 1,4 bonds. Is inhibited via (a) 1,6 bonds

Question 7

2nd (last) step of glycogenolysis

Answer 7

Conversion of G1-P -> G6-P

• done via PGM

Question 8

How are (a) 1,6 branch points cleaved in glycogenolysis?

Answer 8

Glucan transferase & debranching enzyme

Question 9

Glucan transferase

Answer 9

• Removes 3 glucose residue group by cleaving (a) 1,4 bond between the last glucose bound to a(1,6) branch and the 3 residue group.
• transfers three glucose residues to the terminal glucose on the linear chain of glycogen. Bonds via (a) 1,4

Question 10

Debranching enzyme

Answer 10

Removes single branched glucose left over via cleaving (a) 1,6 branched bond.