Control of blood glucose

Question 1

What organ monitors blood glucose concentration

Answer 1

The pancreas

Question 2

What is normal blood glucose concentration

Answer 2

90mg per 100cm^3

Question 3

What do the islets of langerhans secrete

Answer 3

Insulin and glucagon

Question 4

what do alpha cells secrete?

Answer 4

They secrete glucagon

Question 5

What do beta cells secrete?

Answer 5

They secrete insulin

Question 6

INSULIN:

Answer 6

Insulin lowers blood glucose concentration
1) Insulin binds to specific receptors on the cell membrane of liver cells

2) Increases permeability of cell membrane to glucose, so the cells take up more glucose.

3) Insulin activates enzymes that convert glucose into glycogen
(Glycogenesis)

• Glycogen can not be stored in the cytoplasm of
  cells.

Question 7

Does secretion of insulin increase/decreases rate of respiration

Answer 7

• Insulin increases the rate of respiration

Question 8

GLUCAGON:

Answer 8

1) Binds to specific receptors on the cell membrane
2) Glucagon activates enzymes that break down glycogen into glucose. ( Glycogenolysis)
3) Glucagon promotes the formation of glucose from glycerol and amino acids.
- glucagon decreases rate of respiration

Question 9

What is gluconeogenesis?

Answer 9

Process of forming glucose from non- carbohydrates

• This process is activated by glucagon

Glycerol, amino acids -> glucose
^that is gluconeogenesis

Question 10

When there is a rise in blood glucose concentration: ( negative feed backs)

Answer 10

1) Pancreas detects that blood glucose concentration is too high
2) Beta cells secrete insulin and alpha cells secrete glucagon

3) Insulin binds to receptors on liver and muscle cells
- this causes the cell to:
- take up more glucose
- Glycogenesis is activated
- cells respire more glucose

4) Less Glucose in the blood

Question 11

When there is a fall in blood glucose: ( negative feed back)

Answer 11

1) Pancreas detects low concentration of blood glucose
2) Alpha cells secrete glucagon, beta cells secrete insulin

3) Glucagon binds to receptors on liver cells
- Glycogenolysis is activated
- Gluconeogenesis is activated
- cells respire less glucose

4) Cells release glucose into the blood

Question 12

Where is insulin stored in beta cells?

Answer 12

• The insulin in beta cells is stored in vesicles

Question 13

Beta cells secrete insulin (process):

Answer 13

1) When blood glucose concentration is high, more glucose enters beta cells by facilitated diffusion.
2) More glucose in beta cells causes the rate of respiration to increase, causing more ATP to be produced
3) This rise in ATP triggers potassium ion channels to close
4) This means potassium ions cant pass through the membrane, so there is a build up of K+ ions.

5) This makes beta cells less negative due to the high concentration of potassium ions inside the cell.
- So the plasma membrane of beta cells is depolarised

6) This depolarisation triggers calcium ion channels in the membrane to open, so calcium ions diffuse into beta cells
7) This causes vesicles to fuse with the beta cell plasma membrane, and insulin is released by exocytosis.