Lecture 6

Question 1

what are the intracellular signals for the regulation of both glycolysis and gluconeogenesis

Answer 1

small molecule; allosteric effectors

• encourages glycolysis when AMP levels are high
• encourages gluconeogenesis when AMP levels are low

Question 2

what is pyruvate kinase inhibited by?

Answer 2

acetyl CoA
citrate
high levels of ATP

Question 3

What is pyruvate carboxylase activated by?

Answer 3

acetyl CoA

Question 4

What is the main external signal which regulates glycolysis, gluconeogenesis and blood glucose levels?

Answer 4

hormones: insulin and glucagon

Question 5

When is glucagon released?

Answer 5

when blood glucose levels are low

- the pancrease A cells are signalled to secrete glucagon

Question 6

What does glucagon bind to, and what is its’ effect on the cell it has bound to?

Answer 6

• binds to the surface of liver cells
• which leads to a cascade of events which eventually lead to the conversion of glycogen phosphorylase to its active form
• hence glucagon directs liver cells to begin glycogen degradation to glucose

Question 7

When is insulin released?

Answer 7

• it is also released from the pancrease

- released when the blood glucose levels are high

Question 8

What happens when insulin binds to the surface of a cell

Answer 8

increases the uptake of glucose from blood and its conversion to glycogen ; thus decreasing blood glucose level

• also inhibits the free glucose production of the liver into the bloodstream

Question 9

What are the two hormones which are the principle regulators of blood glucose levels?

Answer 9

insulin and glucagon

Question 10

What is epinephrine

Answer 10

• hormone made in the adrenal glands
• affects liver cells similar way that glucagon does
• prepares muscle for sudden burst in activity if required

Question 11

What are the three bypasses?

Answer 11

pyruvate to PEP

FBP to F6P

G6P to glucose

Question 12

how is pyruvate converted to PEP

Answer 12

pyruvate is catalysed by the enzyme pyruvate carboxylase into oxaloacetate then oxaolacetate is converted to PEP by the enzyme phosphoenolpyruvate carboxykinase (using a phosphate from either GTP or ATP); catalyses both phosphorylation and decarboxylation
- uses 2 ATP overall

Question 13

how is FBP converted to F6P

Answer 13

by the enzyme fructose bisphosphate phosphatase

Question 14

How is G6P converted to glucose

Answer 14

by the enzyme glucose 6 phosphate phosphatase

Question 15

What is the enzyme used to convert G6P to glucose in the liver

Answer 15

glucokinase

Question 16

What is the enzyme used to convert FBP to F6P

Answer 16

fructose 1,6 bisphosphatase

Question 17

What enzyme is used to convert pyruvate to PEP

Answer 17

pyruvate to oxaloacetate (enzyme pyruvate carboxylase)

oxaloacetate to PEP (PEPCK)

Question 18

Where can’t gluconeogenesis occur?

Answer 18

skeletal muscle

Question 19

Where can gluconeogenesis occur?

Answer 19

liver