3.6.4.2 Control of blood glucose concentration

Question 1

Why does you blood glucose concentration fall after exercise?

Answer 1

More glucose is used in respiration to release energy.

Question 2

What’s the process of breaking down glycogen into glucose called?

Answer 2

Glycogenolysis

Question 3

Give two effects of glucagon on liver cells.

Answer 3

• Activates enzymes that break down glycogen into glucose (glycogenolysis).
• Activates enzymes that are involved in formation of glucose from glycerol and amino acids (gluconeogenesis).

Question 4

What type of feedback mechanism is involved in the control of blood glucose concentration?
[1 mark]

Answer 4

• Negative feedback
• …because the pancreas secretes hormones that return blood glucose conc. to normal if it is detected as being too high or too low.

Question 5

Describe the role of insulin in this feedback mechanism.

[3 marks]

Answer 5

• Insulin binds to specific receptors on muscle cells causing them to become more permeable to glucose, so more is absorbed from the blood.
• Insulin activates glycogenesis, so that glucose can be stored as glycogen.
• Insulin causes the rate of respiration of glucose to increase, so that more glucose is used up.

Question 6

Explain how glycogenolysis is triggered inside the cell when hormones, glucagon and adrenaline, bind to receptors on the cell surface.
[3 marks]

Answer 6

• When adrenaline and glucagon bind to the receptors on the cell membrane they activate an enzyme called adenylate cyclase.
• Activated adenylate cyclase activates ATP into cAMP, a second messenger.
• cAMP activates protein kinase A, which activates a cascade that breaks down glycogen into glucose.