Explain why it is important for the body to maintain a constant blood glucose concentration.

Cambridge International IGCSE Biology (0610) — 14.4 Homeostasis · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

If blood glucose is too high, the blood’s water potential falls, so water leaves cells by osmosis, causing them to shrink or die. If blood glucose is too low, the blood’s water potential rises, so water enters cells by osmosis, causing them to burst or lyse. Maintaining a constant blood glucose level also gives cells a reliable source of energy.

Examiner tips

Use the term ‘water potential’ and explain the osmotic effect for each case.
Mention both cell damage outcomes (shrinkage/dying and bursting/lysis).
Show the link between glucose concentration and energy supply.
Keep the answer concise and directly address the question.

Common mistakes

Confusing high glucose with high water potential instead of low.
Failing to mention the cell damage (shrinkage or bursting).
Using vague phrases like ‘good for cells’ instead of ‘reliable source of energy’.

Mark scheme (4 marks)

If blood glucose concentration is too high, water potential of the blood falls / becomes very low
Water moves out of cells by osmosis, causing cells to shrink / die
If blood glucose concentration is too low, water potential of the blood is high / increases
Water moves into cells by osmosis, causing cells to burst / lyse; OR a constant blood glucose level provides a reliable / constant source of energy for cells

Key terms in this question

blood glucose concentration