Glycogenesis and Glycogenolysis

Question 1

Four enzymes involved in glycogen synthesis in order of function

Answer 1

Phosphoglucomutase: converts G6P –> G1P

UDP-Pyrophosphatase converts G1P + UDP –> Glucose-UDP

Glycogen Synthase (rate limiting) attached UDP-Glu to existing glucost chain at nonreducing end

Glycosyl 4:6 transferase breaks glycogen branch off @ every 11 monomers and reattaches 7-monomer long brach to alpha-1,6-glycosidic branch elsewhere

Question 2

explain 10:1 ratio

Answer 2

glycogen phosphorylase/B6 cleave nonreducing end glycogen monomers until they are 4 glucose monomers to the alpha-1,6 glycosidic bond.

debranching enzyme removes 3/4, adds them to the brain glycogen chain; finally debranching enzyme cuts alpha 1,6 glycosidic bond to release a single free glucose.

Glycogen phosphorylase (GP): removes 7 glucose-1-phosphates.

debranching enzyme removes 3 alpha 1,4 glyco and adds to main chain

debranching enzyme removes last glucose at a-1,6 bond, released as glucose.

10/1

Question 3

the enzymes involved in glycogen break down in order and function

Answer 3

glycogen phosphorylase cleaves glycogen monomers into glucose-1-phosphates until 4 monomers from alpha-1,6-glycosidic branching site

4:4 transferase cleaves 3, leaving one last moner; transfers 3 to main brain and cleaves remaining monomer as glucose (not glucose-1-phosphate)

Question 4

what enzymes are not found in myocytes or cardiocytes

Answer 4

pyruvate carboxylase
phosphoenolpyruvate carboxykinase
Fructose 1,6 Bisphosphatase
Glucose-6-Phosphatase

Question 5

two key enzymes controlling rate of glycogen degradation and synthesis

Answer 5

1) glycogen synthase

2) glycogen phosphorylase

Question 6

Two conditions under which glycogenolysis will be favored

Answer 6

1) glucagon

2) exercise (Ca and AMP levels increased)