Chapter 18

Question 1

Action of Glycogen Phosphorylase

Answer 1

• Activated by phosphorylation
• Catalyzes the rate-limiting step in glucogenolysis- the phosphorolytic cleavage of the 1→4 linkages of glycogen to yeild glucose 1-phosphate
• Requires pyridoxal phosphate as coenzyme

Question 2

Action of Glycogen Synthase

Answer 2

• Activated by dephosphorylation
• Catalyzes the formation of a glycosidic bond between C-1 of the glucose of UDPGlc & C-4 of a terminal glucose residue of glycogen, liberating UDP
• Responsible for making the alpha (1→4) linkages in glycogen
• Cannot initiate chain synthesis using free glucose. Can only extend a pre-existing chain
• In the absence of a pre-existing chain, a protein called glycogenin can serve as acceptor for creating the chain
• Contains tyrosine as the residue

Question 3

Action of Glucagon Epinephrine

Answer 3

Increases [cAMP]

Question 4

Action of Insulin

Answer 4

Decreases [cAMP] only after it has been raised by glucagon epinephrine

Question 5

Action of cAMP

Answer 5

• Phosphorylation is increased in response to cAMP
• Activates Glycogen Phosphorylase
• Deactivates Glycogen Synthase

Question 6

Glycogen Storage Diseases

Answer 6

• Von Gierke Disease
• Limit Dextrinosis, Forbe or Cori Disease
• Hers Disease

Question 7

Von Gierke Disease

Answer 7

Glucose-6-Phosphatase deficiency

Question 8

Limit Dextrinosis, Forbe or Cori Disease

Answer 8

Liver & Muscle Debranching Enzyme deficiency

Question 9

Hers Disease

Answer 9

Liver Phosphorylase deficiency

Question 10

Action of Protein Posphatase-1

Answer 10

It dephosphorylates & inactivates both Phosphorylase a & Phosphorylase Kinase a

Question 11

The 3 Regulatory Enzymes for Glycolysis

Answer 11

• Hexokinase
• Phosphofructokinase
• Pyruvate Kinase