[2] Lecture 8: Glycogen Metabolism Flashcards Preview

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Flashcards in [2] Lecture 8: Glycogen Metabolism Deck (87)
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1

Osmotically inactive, readily mobilized form of glucose.
12 layers of glu. W/ approx. 55,000 glucose residues.
Linked w/ alpha-1,4 glycosidic bonds and branched w/ alpha-1,6 glycosidic bonds.

Structure of glycogen

2

Glycogen End that contain a terminal glucose w/ a free hydroxyl group at C4

Non-reducing end

3

Glycogen end Has glucose monomer connected to a protein called glycogenin

Reducing end

4

This protein is connected to the reducing end of glycogen:

Glycogenin

5

Glycogenin helps to make a ________, which is crucial for glycogen synthesis.

Primer

6

Enzyme involved in converting glucose to glycogen.

Acts as a primer.

Glycogenin

7

Where is glycogen stored?

Liver
And
Muscle

8

Liver stores 10% by weight and muscle stores 2% by weight, which holds more?

Muscle! More SA of muscle than liver

9

What doesglycogen look like on photomicrogrpah?

Granules

Glycogen granules

10

Glycogen contains what for its own metabolism?

Enzymes...more accurate timing

11

Regulates overall BG levels

Crucial for brain function

Liver glycogen

12

Provides reservoir of fuel [glucose] for physical activity for muscle

Muscle glycogen

13

Regulated storage and release of glycogen

Synthesis and degradation of glycogen involve diff. Pathways

Both pathways regulated independently

Glycogen metabolism

14

3 regulating factors for glycogen metabolism

Allosteric control-modulators

Covalent modification-P's

Hormonal control

15

Glycogen broken down to release G-1-P-glycogen remnant-remodeled to allow further degradation->

Then, G-1-P converted to G-6-P

Glycogenolysis

16

3 fates of glycogenolysis:

glycolysis

Free glucose for release into bloodstream

Pentose phosphate pathway-NADPH and ribose derivative

17

Catalyzes the cleavage of glycogen- rate limiting step

Chain shortening occurs at the non-reducing end

Adds an orthophosphate and releases a glucose residue as G-1-P

Uses a pyridoxal phosphate (vitB-6) as a cofactor

Glycogen phosphorylase (GP)

18

When does phosphorylation cease?

When GP gets w/in 4 Residues of the alpha-1,6 linkage of a branch point

19

Transfers a block of 3 of the remaining 4 glucose to the non-reducing end of the main chain forming an alpha-1,4 bond

Which enzyme is this involved in glycogenolysis?

Transferase

20

Cleaves the alpha-1,6 bond of the single remaining glucose residue to release free glucose.

Which enzyme is this involved in glycogenolysis?

Alpha-1,6 glucosidase

(Debranching enzyme)

21

Whic 2 enzymes are responsible for converting branched glycogen into a linear structure for further action by glycogen phosphoylase?

Transferase

Alpha-1,6 glucosidase

22

What enzyme converts G-1-P to G-6-P?

Phosphoglucomutase

23

A phosphorylation group is transferred from the enzyme to the substrate, and a different phosphoryl group is transferred back to restore the enzyme to its initial state

Which enzyme?

Phosphoglucomutase

24

How is G-6-P converted to glucose?

It is shipped to the liver b/c it is the only place where you can find g-6-phosphatase

25

What're the 2 ways glycogen phosphoryloase is regulated?>

Allosteric factors: energy signals of the cell

Reversible phosphorylation (hormones)

26

Glycogen phosphorylase exists in 2 forms

A and B

27

Liver GP is predominantly which form of GP?

Liver is phosphyrlase A and it exists mostly in R relaxed state

28

Muscle GP is predominantly which form?

Phosphorylase B mostly exists in T tense state

29

Liver and muscle forms of GP are products of seperate genes. What is this called?

Isozymes

30

Form A=
Form B=

A=relaxed

B=tense