Glycogen Metabolism Flashcards Preview

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Flashcards in Glycogen Metabolism Deck (11):
1

Glycogen

Storage form of glucose in animals
Mostly in liver and muscle cells

2

Step 1 of glycogen synthesis

Glucose 6-phosphate -> glucose 1-phosphate
Enzyme: phosphoglucomutase

3

Step 2 of glycogen synthesis

Glucose 1-phosphate -> UDP-glucose
Enzyme: UDP-glucose pyrophosphorylase

4

Step 3 of glycogen synthesis

Addition of UDP-glucose to the growing glycogen polymer
Enzyme: glycogen synthase

5

Glycogen degradation

Glycogen phosphorylase catalyzes the removal of glucose residues from the non-reducing ends of glycogen (phosphorolysis reaction: transfer of glucose residue to phosphate)

6

Limit dextrin

4-residue branched fork of glycogen formed from degradation of one end
4-alpha-glucanotransferase translocates 3 residues to another end
Amylo-1,6-glucosidase can remove lone branched glucose

7

Insulin

Secreted from beta-cells in the pancreas when blood glucose levels increase
Stimulates glycogen synthesis

8

Glucagon

Secreted from alpha-cells in the pancreas when blood glucose levels decrease
Stimulates glycogen degradation

9

Epinephrine

Secreted by adrenal gland as part of the "fight or flight" response
Promotes glycogen degradation
Shorter term effect than insulin and glucagon

10

How glycogen synthesis and degradation are regulated

Reciprocally regulated (1 is activated, other is deactivated)
Phosphorylation of enzymes by protein kinases and protein phosphatases

11

Glycogen regulation by glucose

Glucose stimulates glycogen synthesis