Control of blood glucose concentration

Question 1

Name some factors that influence blood glucose concentration:

Answer 1

• Diet
• Exercise
• Insulin, glucagon, and adrenalin levels

Question 2

What is glycogenesis?

Answer 2

When excess glucose is converted to glycogen in the liver.

Question 3

What is glycogenolysis?

Answer 3

Breakdown of glycogen back to glucose in the liver.

Question 4

What is gluconeogenesis?

Answer 4

Formation of glucose from non-carbohydrate stores in the liver e.g. amino acids + glycerol. Occurs when blood glucose concentration is low despite glycogenolysis.

Question 5

Describe insulin action and how it decreases blood glucose concentration (3 ways):

Answer 5

Insulin is secreted by beta cells when blood glucose concentration is too high. It decreases blood glucose in these ways:

• Binds to receptors on target cells and changes the tertiary structure so more glucose is absorbed by facilitated diffusion.
• Produces more carrier proteins so even more glucose is absorbed.
• Activates enzymes involved in glycogenesis.

Question 6

Describe glucagon action and how it increases blood glucose concentration (2 ways):

Answer 6

Glucagon is secreted by alpha cells when blood glucose concentration is too low. It increases blood glucose concentration in these ways:

• attaching to receptors on the surfaces of target cells (second messenger model)
• activates enzymes involved in glycogenolysis and gluconeogenesis in the liver.

Question 7

Describe the second messenger model for glucagon and adrenaline action:

Answer 7

1. Glucagon/adrenaline attaches to receptors on the surface of cells/
2. This stimulates adenylate cyclase to convert ATP to cyclic AMP (cAMP).
3. cAMP then acts as a second messenger and activates an enzyme called protein kinase which hydrolyses glycogen to glucose.
4. Also activates enzymes for gluconeogenesis.

Question 8

What is a second messenger model?

Answer 8

Molecules inside a cell transmit signals intracellularly from the binding of an extracellular molecule to a receptor.

Question 9

What is type 1 and type 2 diabetes?

Answer 9

Type 1 diabetes is when you cannot produce insulin and is often caused by an autoimmune disease that attacks beta cells in the islets of Langerhan. Type 2 diabetes is when target cell receptors no longer respond to insulin. Usually develops in adulthood due to poor diet and obesity.

Question 10

What are the treatments for type 1 and type 2 diabetes?

Answer 10

Type 1 - insulin injections

Type 2 - regulating the uptake of carbohydrates and increasing exercise

Question 11

Explain how glycogenesis causes a decrease in blood glucose concentration?

Answer 11

Glycogenesis means glucose in liver cells is being converted to glycogen which is insoluble. This creates a diffusion gradient and glucose in the blood diffuses into the cell.