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Lecture 14 Slides

Glycogen: the glucose buffer…

Glycogen granules

~ 1600 glucose monomers per granule

fig 7-14

Glycogen in real life…

How is glycogen synthesized?

-sequential addition of glucose to a growing a1-4 linked linear polymer

-creation of branches composed of a1-6 linkages

glycogenin, then glycogen synthase

branching enzyme

O1

234

5

6

reducingend

non-reducing

end

Glucose ends…

polymer ends…

fig 7-14

pg 597

fig 15-29

addition of UDP carrier to glucose-1-P

fig 15-30

addition of glucose monomersto the growing glycogen chain

fig 15-31

Glycogen branching enzyme creates branches

fig 15-9

Glycogen branching enzyme creates branches

10a1 4 3

7 a1 6

a1 4

How is glycogen broken down?

-sequential removal of glucose-1P from the non-reducing end

-dismantling of those pesky branches

glycogen phosphorylase

debranching enzyme

fig 14-11

fig 15-26

debranching enzyme removes branches

4

4 a1 6

a1 47a1 4

1 a1 67a1 4

freeglucose

Debranching enzyme removes branches

transferaseactivity

a1-6glucosidase

Ask… ortxt: 858-333-6376

fig 15-36

Allosteric control of glycogen phosphorylase

Hormonal control of glycogen phosphorylase

fig 15-34

fig 15-37

regulation ofglycogen synthaseby phos-phorylationas well…

fig 23-13

Liver glucosemetabolism

Blood glucoselevel is criticaland stringentlyregulated

fig 23-23

fig 23-20

The Coricycle

Liver as a "glucostat"

high blood glucose

low blood glucose

Glucagon: the hormone of starvation

phosphorylation of enzymes

alteration of fructose 2,6 bis P

Insulin: the hormone of plenty

fig 23-24

b cell glucose sensing: an ATP gated channel