Chapter 15: Hormonal Communication

Question 1

Why is it important that the patient had not eaten for at least 8 hours before a diabetes test (1 mark)

Answer 1

time is needed to restore normal blood glucose concentration/ for insulin to act fully

Question 2

Describe how glucagon is involved in the regulation of blood glucose concentration in a person who is able to regulate their blood glucose concentration regularly (4 marks)

Answer 2

Initially when blood glucose levels drop below their set level this is detected by the alpha cells in the islets of Langerhans in the pancreas leading to secretion of glucagon.

this promotes the conversion of glucose into glycogen through glycogenesis occurring in liver and muscle cells

gluconeogenesis also occurs in the liver which is the conversion of triglycerides into fatty acids which can then be converted into glucose

negative feedback can reduce / inhibit glucagon secretion once levels have been returned to normal

Question 3

The adrenaline receptor is one of a class of receptors known as GPCRs.

The glucagon receptor on liver cells is another type of GPCR.

Glucagon stimulates conversion of glycogen to glucose in liver cells.
What is the action of glucagon? (1 mark)

Answer 3

When glucagon binds to its receptor it stimulates the conversion of ATP to cyclic AMP

Question 4

After the initial release of insulin from the beta cell, insulin secretion continues even when there is no further glucose intake.

Suggest and explain why the cell continues to secrete insulin.

Answer 4

1 continues to be secreted as long as blood / plasma, glucose
concentration, remains high / is higher than normal;

2 sufficient ATP is still present and so K+ channels remain closed;

3 exocytosis still being triggered by, calcium ions / Ca2+;