Describe the roles of insulin and glucagon in maintaining a stable blood glucose concentration in the body.

WJEC A-Level Biology (Wales) — 4.4 Application of reproduction and genetics · Describe · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

After eating a meal containing carbohydrates, the concentration of glucose in the blood rises. The body must respond to restore the optimum blood glucose level. Later, during exercise, blood glucose levels begin to fall and the body must respond again.

Model answer (5 marks)

Insulin is produced by the pancreas and lowers blood glucose by increasing cellular uptake of glucose.
Insulin also signals the liver to convert excess glucose into glycogen for storage.
Glucagon is produced by the pancreas and raises blood glucose.
Glucagon stimulates the liver to break down glycogen into glucose.
These hormones act in opposition to keep blood glucose within a narrow range.

Examiner tips

Use the exact terms ‘insulin’, ‘glucagon’, ‘pancreas’, ‘glycogen’, ‘liver’. Show the opposite actions (lower vs raise glucose) to hit all points. Keep each point short and to the point to fit the 5‑mark limit.

Common mistakes

Confusing the source of insulin or glucagon (e.g. saying ‘liver’ instead of ‘pancreas’). Omitting the action of insulin on liver glycogen storage. Using vague language like ‘helps’ instead of ‘causes’ or ‘increases’.”

Mark scheme (5 marks)

Insulin is produced/secreted by the pancreas
Insulin decreases blood glucose concentration by increasing uptake of glucose into cells
Insulin causes the liver to convert glucose into glycogen for storage
Glucagon is produced/secreted by the pancreas and increases blood glucose concentration
Glucagon causes glycogen to be converted into glucose (in the liver)

Key terms in this question

insulin · glucagon · glucose