Week 14: Glycogenesis & Glycogenolysis

Question 1

What is glycogenesis?

Answer 1

synthesis of glycogen from glucose

Question 2

What is glycogenolysis?

Answer 2

breakdown of glycogen to form glucose

When glucose levels are low

Question 3

What is glycogen?

Answer 3

Main storage form of glucose in liver and muscle cell

Question 4

When is liver glycogen broken down?

Answer 4

between meals

Question 5

Why is liver glycogen released?

Answer 5

released to maintain blood glucose levels for red blood cells and brain

Question 6

What type of glycogen maintains blood glucose levels?

Answer 6

liver glycogen

Question 7

When does muscle glycogen provide energy?

Answer 7

during bursts of physical activity

Question 8

What influences glycogenolysis activity?

Answer 8

fluctuates depending on meal times

Question 9

Recall where glycogenolysis fluctuates?

Answer 9

• Decreases at breakfast but increases shortly after
• peaks at lunch
• decreases in-between

Question 10

What happens to the % of source of blood sugar according to dietary?

Answer 10

after meal time increases

Question 11

What is the primary source of glucose overnight?

Answer 11

gluconeogenesis

when hepatic glycogen is depleted

Question 12

What are the monomers of glycogen?

Answer 12

glucose molecules joined by alpha 1-4 glycosidic links

Question 13

What link are the branches of glycogen on?

Answer 13

introduced by alpha-1,6 glycosidic links

Question 14

What is the nonreduing end of glycogen?

Answer 14

provides directionality to glycogen

Question 15

What are the two pathways glucose-6-phosphate can go?

Answer 15

1. glycolysis

2. glucose-1 phosphate –> glycogen synthesis

Question 16

What can glucose residues only be added to?

Answer 16

existing glycogen chain

Question 17

What is the intermediate form of glucose?

Answer 17

UDP-glucose

active form of glucose

Question 18

What does the activated form of glucose allow it to do?

Answer 18

joining to existing form of glycogen

Question 19

What does a glycogen residue require to bind to glycogen chain?

Answer 19

a certain amount of glycogen to be present i.e glycogen primer

Question 20

How many glucose residues does a glucose primer contain?

Answer 20

4

Question 21

What is the primer attached to?

Answer 21

covalently attached to a protein called glycogenin

Question 22

What enzyme converts G6P to G1P?

Answer 22

phosphoglucomutase

transfers phosphate on C6 to C1

Question 23

What converts G1P to UDP-glucose

Answer 23

UDP-glucose pyrophosphorylase

Question 24

What enzyme converts UDP-glucose to glycogen?

Answer 24

glycogen synthase

Question 25

What can simple precursors be first converted to?

Answer 25

activated intermediates

Question 26

Is G1P+UTP --> UDP+ pyrophosphate (PPi) reversible?

Answer 26

YES

Question 27

What pulls the formation of UDP glucose forward?

Answer 27

the very active pyrophosphatase hydrolyses PPi so cant reverse anymore

Question 28

What is the rate limiting enzyme of glycogen synthesis?

Answer 28

glycogen synthase

Question 29

Can glycogen synthase introduce branches?

Answer 29

can not introduce branches | can not start new molecules

Question 30

How many glucose molecules can glycogen synthase add to glycogen?

Answer 30

1 at s time

Question 31

What is the branching enzyme?

Answer 31

transglycosylase

Question 32

What bond will transglycoylse add a glucose?

Answer 32

alpha 1,6-glycosidic linkage on carbon 6

Question 33

How often is a new branch created?

Answer 33

every 10 glucose residues

Question 34

What regulates glycogenesis?

Answer 34

insulin & glucagon

Question 35

What regulates level of the hormone?

Answer 35

stimuli= blood glucose levels

Question 36

When does glycogenesis occur?

Answer 36

immediately after meals

Question 37

What is high blood glucose levels also called?

Answer 37

hyperglycaemia

Question 38

What hormone activates glycogen synthase? hyperglycaemia

Answer 38

insulin

Question 39

What hormone inactivates glycogen synthase? hypoglycaemia

Answer 39

glucagon

Question 40

What is glycogenolysis?

Answer 40

When we need to utilise the energy stored as glycogen

Question 41

What catalyses glycogenolysis?

Answer 41

glycogen phosphorylase

Question 42

What is the rate limiting step in glycogenolysis?

Answer 42

degradation of glucose to glucose-1-phosphate& then G6P

Question 43

How many glucose molecules can be cleaved at a a time?

Answer 43

1

Question 44

What happens when G6P is dephosphorylated in the liver?

Answer 44

dephosphorylated to glucose and released into blood stream

Question 45

Can (skeletal) muscle cells dephosphorylate G6P?

Answer 45

NO, instead used to provide energy via glycolysis & TCA cycle

Question 46

What does glycogenolysis depend on?

Answer 46

demand for blood glucose

Question 47

What hormones regulate glycogenolysis?

Answer 47

hypoglycaemia, stress+hypoglycaemia, stress, hyperglycaemia

Question 48

What is the source of glucagon?

Answer 48

pancreatic alpha cells

Question 49

What hormones increases blood glucose levels in glycogenolysis?

Answer 49

glucagon, adrenaline, cortisol

Question 50

What hormones decreases blood glucose levels in glycogenolysis?

Answer 50

insulin

Question 51

What is the source of insulin?

Answer 51

pancreatic beta cells

Question 52

What is the source of adrenaline?

Answer 52

adrenal medulla

Question 53

What is the source of cortisol?

Answer 53

adrenal cortex