Chapter 18 Flashcards
1
Q
Action of Glycogen Phosphorylase
A
- 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
2
Q
Action of Glycogen Synthase
A
- 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
3
Q
Action of Glucagon Epinephrine
A
Increases [cAMP]
4
Q
Action of Insulin
A
Decreases [cAMP] only after it has been raised by glucagon epinephrine
5
Q
Action of cAMP
A
- Phosphorylation is increased in response to cAMP
- Activates Glycogen Phosphorylase
- Deactivates Glycogen Synthase
6
Q
Glycogen Storage Diseases
A
- Von Gierke Disease
- Limit Dextrinosis, Forbe or Cori Disease
- Hers Disease
7
Q
Von Gierke Disease
A
Glucose-6-Phosphatase deficiency
8
Q
Limit Dextrinosis, Forbe or Cori Disease
A
Liver & Muscle Debranching Enzyme deficiency
9
Q
Hers Disease
A
Liver Phosphorylase deficiency
10
Q
Action of Protein Posphatase-1
A
It dephosphorylates & inactivates both Phosphorylase a & Phosphorylase Kinase a
11
Q
The 3 Regulatory Enzymes for Glycolysis
A
- Hexokinase
- Phosphofructokinase
- Pyruvate Kinase
