Explain why the human body needs both a circulatory system and blood to supply cells with the substances they need.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The circulatory system, consisting of the heart and blood vessels, pumps blood through the body.
Blood carries dissolved nutrients such as glucose and oxygen to cells.
It also removes waste products like carbon dioxide from cells.
Because cells are too far from the lungs and gut to depend on simple diffusion, an active transport system is required to supply and remove substances efficiently.
Blood carries dissolved nutrients such as glucose and oxygen to cells.
It also removes waste products like carbon dioxide from cells.
Because cells are too far from the lungs and gut to depend on simple diffusion, an active transport system is required to supply and remove substances efficiently.
Examiner tips
- Use the exact terms ‘circulatory system’, ‘blood’, ‘nutrients’, ‘oxygen’, ‘waste products’ and explain the role of each.
- Show the cause–effect link: transport system → delivery of nutrients/oxygen and removal of waste.
- Keep the answer concise and structured, matching the four points of the mark scheme.
Common mistakes
- Confusing the heart with blood vessels or vice‑versa.
- Omitting the removal of waste products or the need for active transport.
- Using vague language such as ‘carry’ without specifying nutrients or waste.
Mark scheme (4 marks)
- The circulatory system (heart and blood vessels) transports blood around the body
- Blood carries/transports dissolved nutrients (e.g. glucose) and oxygen to cells
- Blood removes waste products (e.g. carbon dioxide) from cells
- Cells are too far from the exchange surfaces (lungs/gut) to rely on diffusion alone, so an active transport/circulation system is needed
Key terms in this question
Related
- All Eduqas GCSE Biology revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →