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Flashcards in Glycogen Metabolism Deck (39):
1

How is glycogen synthesis favored

by insulin - in both liver and muscle

2

What does the liver do with glycogen

releases as free glucose in flight or fight situation

3

what does the muscle do with glycogen?

stores it for energy metabolism

4

what regulates glycogen degradation in the liver/

hormones - during fasting or low insulin/glucagon ratio - glucose is released into the blood

5

what is glycogen degradation linked to in skeletal muscle

muscle contraction - independent of hormones (you don't wanna wait for hormones to have a contraction!) - G-6-P is used in glycolysis

6

what stimulates glycogenolysis in liver and muscle?

epinepherine = hormone

7

what takes place at the same time at low insulin levels?

gluconeogensis and glycogen degradation

8

what happens at the same time when the muscle needs ATP

glycogen degradaiton and glycolysis

9

when does the muscles glycogen store deplete?

not during fasting - during exercise!

10

where is glycogen mainly found in the body?

largest amount = skeletal muscle
highest concentration = liver

11

what can glycogen storage diseases affect?

liver only, or muscle only or BOTH

12

what is the purpose of glycogen metabolism (2)

synthesis of glycogen when G-6-P is abundant - high insulin in liver and muscle

degradatino of glycogen when G-6-P is needed - low insulin in liver/muscle contraction in muscle

13

in what cellular compartment is glycogen degraded and metabolized?

in the cytosol
glycogen is stored in cytosolic granules of liver and muscle

14

what is special about glycogen metabolism?

many enzymes can act at the same time on glycogen because of the branched structure - tightly regulated thouhg (glycogen phophorylases vs. glycogen synthase)

15

what is glycogenic?

core protein surrounded by branches

16

what do both gylcogen syntehsis and glycogen degradation use?

glucose 6-P and Glucose-1-P - reversibly formed by phosphoglucomutase

17

what is the highly activated form of glucose used for synthesis of glycogen? how is it made?

UDP-glucose
made from glucose-1-P + UTP

18

what is glycogen syntheases primer needed to link UDP-glucose together

some branched glyogen chains that are not totally degraded - then it makes the alpha 1,4 bonds

19

when alll the glycogen chains are degraded, what do we need?

glycogenin protein

20

what does glycogenin do?

self-glucosylating enzyme (similar to ser and thr) uses UDP-glucose and add like 8 glucose units to its own try residue ---EXCEPTION

21

what is the point of having so many branches?

they improve solubility of glycogen
allow for accelerated rates of glycogen synthesis or degradation

22

what does 4:6 transferase do?

removes a chain of about 8 glucosyl residues from the nonreducing end (by cleaving hte alpha 1-4 bond) and attached it to a non-temrinal glucosyl residue by an alpha 1-6 linkage

23

when do you want glycogen sythase to be active?

insulin ruling

24

what coenzyme does phosphorolytical cleavage of glycogen to G-1-P need>

pyridoxal phosphate (PLP) fromed from vitamin B6

25

what is pyridoxal phosphate usually used for?

amino acid metabolism - this is an exception

26

why is it important to get to a glycogen store in muscle?

it saves an ATP because you don't need to convert glucose to G-6-P, you just have G-1-P and you can change it to G-6-P without using an ATP

27

in both liver and muscle, how is glycogen synthease activated?

by glucose-6-P

28

what inhibits glycogen degradation (glycogen phosphorylase) in muscle and liver?

glucose-6-P
ATP

29

what inhibits glycogen degradation in liver only?

glucose

30

what activates degradation in muscle only?

AMP (generated by muscle contraction)

31

what is limit dextrin?

intermediate in glycogen degradation which is a substrate for debranching enzymes

32

what does 4:4 transferase do

leads from limit dextrin to longer branches

33

what does 1:6 glucosidase do?

cleaves the alpha 1-6 bond at the branch point and generates 1 free glucose molecule

34

what does gylcogen degradation generate?

G-1-P and some free glucose

35

what can protein kinase A only phosphorylate?

glycogen phosphorylase kinase

36

what is glycogen phospohrylase kinase?

the enzyme which phosphorylates and activates glycogen phosphorylase b which makes it a

37

what does glyocgen phosphorylase kinase have

calcium for allosteric activation and calmodulin

38

what does AMP allosterically activate?

glycogen phophorylase

39

what does glycogen synthase do (in general)

takes 2 UDP-glucose and smushes them together! - but it needs a primer to do that!