Glycogen breakdown

Question 1

We cant make glucose from..?

Answer 1

from acetyl CoA or fatty acids (except from a bit of Propionyl CoA)

Question 2

• We can get glucose from

Answer 2

glycerol & amino acids

Question 3

What happens after glycogen reserves are depleted

Answer 3

gluconeogenesis

Question 4

Glycogen is broken down from the non-reducing terminals when:

Answer 4

• Blood glucose levels begin to fall (in the liver)

- When muscles need glucose for ATP production (breakdown in liver & muscles

Question 5

how is glycogen breakdown (reaction)?

Answer 5

glycogen + pi –> glucose 1-phophate (energy rish molecule) + glycogen (n-1 residues)

Question 6

what controls this breakdown process?

Answer 6

Glycogen phosphorylase is activated by glucagon –> only acts on the liver whilst fasting

Question 7

Glycogen phosphorylase stops cleaving when

Answer 7

when it gets within 4 residues of a branch point

Question 8

what happens when glycogen hits a branching point

Answer 8

Enzyme transfers 3 glucose units to the end of the glycogen molecule.
Enzyme hydrolyses off the single glucose
Phosphorylase can now start again in breaking down the glycogen chain

Question 9

Glycogen breakdown generates

Answer 9

mainly glucose 1 – phosphate with a little bit of glucose (ratio of 8:1)

Question 10

Fate of glucose 1 phosphate and glucose in the liver

Answer 10

Glucose 1-phosphate c –> glucose 6 phosphate by phosphoglucomutase and then into glucose by glucose- 6 phosphate (h20 –> Pi)
Glucose then released into blood to maintain glucose levels between meals, sleeping, early fasting

Question 11

why is the Fate of glucose 1-phosphate and glucose in the muscle different

Answer 11

The muscle does not contain any glucose 6 phosphatase & can’t convert glucose 6-phosphate into glucose

Question 12

what is the Fate of glucose 1-phosphate and glucose in the muscle

Answer 12

Any glucose released is converted into glucose 6 – phosphate by hexokinase by phosphorylation
- Glucose 6 – phosphate is trapped inside the muscle cell and is used in glycolysis for ATP production

Question 13

allosteric control regulates glycogen metabolism ..

Answer 13

oAMP allosterically stimulates glycogen breakdown

oATP inhibits glycogen breakdown

Question 14

role of adrenaline and glucagon

Answer 14

stimulate glycogen breakdown & inhibits glycogen synthesis

Question 15

hormone control of glucagon and adrenaline pathway

Answer 15

• hormone attachment to receptor causes conformational change
• which activates adneylate cyclase
• which converts ATP–> cAMP
• which activate protein kinase
• which phosphorylates phosphorylase kinase which activate glycogen phosphorylase
• AND inactive glyc0gen synthase

Question 16

role of Ca2 plus in hormone control of glycogen breakdown inhibition

Answer 16

promotes activation of phophorylase kinase

Question 17

Insulin pathway

Answer 17

• insulin binds to tyrose kinase
• activation of protein kinase
• activation of phophoprotein phosphate 1
• glycogen synthase b –> glycogen synthase a
• AND glycogen ohspohorylase a –.> B (inactive)