Glycogen synthesis and metabolism

Question 1

What is glycogen?

Answer 1

polysaccharide- glucose monomers
Storage of glucose
Stored in-Liver (100g) and muscle (400g)

Question 2

Function of liver and muscle glycogen

Answer 2

Liver- blood glucose

Muscle- Muscle contractions

Question 3

Why store glucose as glycogen?

Answer 3

Glucose buffer
Less osmotically active
Easier to mobilise to and from liver and muscle

Question 4

Describe the synthesis of glycogen

Answer 4

Primer glycogenin is need
Synthesis starts with first glucose attached to glycogenin
Chain of glucose molecules is attached alpha 1,4-glycosidic bond between carbon atom
1,6 carbon link forms branches

Question 5

Which bond attaches glucose together to form glycogen?

Answer 5

alpha 1,4-glycosidic bond between carbon atom

Question 6

Which bond forms branches in glycogen production

Answer 6

1,6 carbon link

Question 7

How is glycogen stored and why is it stored like this?

Answer 7

Stored as macroglycogen

Large molecule- more places for enzymes to attach and break it down

Question 8

When is glycogen produced and stored?

Answer 8

During rest and and high glucose concentrations

Question 9

Describe glycogenolysis (glycogen break down)

Answer 9

1. Branches broken down using Alpha-1-6-glucosidase
2. Terminal glucose by breaking 1,4 links using glycogen phosphorylase
3. conversion of G1P to G6P – enzyme phosphoglucomutase

Question 10

Describe Glycogenolysis in the liver

Answer 10

G6P de-phosphorylated into glucose
Glucose enters blood stream
to maintain glucose homeostasis.
Occurs during fasting

Question 11

Describe Glycogenolysis in the muscles

Answer 11

All glycogen goes directly into (G-6-P) glycolysis to produce energy so never becomes glucose.
medium –term course of energy

Question 12

What can happen to lactate produced by glycolysis during anaerobic respiration?

Answer 12

recycled via the Cori cycle.

Question 13

Which molecules control glycogen metabolsim?

Answer 13

Insulin (liver and muscle) and glycogen (liver)

Adrenaline and calcium (muscle only) Released by muscle during activity

Question 14

Function of insulin in glycogen metabolism?

Answer 14

Released after a meal
Stimulates glycogen production in 2 ways-
1. Activates glycogen synthase
2. Inhibits glycogen phosphorylase

Question 15

Function of glucagon in glycogen metabolism?

Answer 15

Released between meals
Stimulates glycogen break down in 2 ways:
1. inhibits glycogen synthase
2. stimulates glycogen phosphorylase

Question 16

What controls the activation and inhibition of glycogen synthase and glycogen phosphorylase?

Answer 16

Addition and removal of a phosphate group
Gs is inhibited by PO4
GP is activated by PO4