Red blood cells and platelets are two components of blood. Describe how the structure of red blood cells and platelets is adapted to their functions in transporting substances and repairing damage in the human body.

Eduqas A-Level Biology — 2.3 Adaptations for transport in plants and animals · Describe · 5 marks · View as Markdown

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

Model answer (5 marks)

Red blood cells contain haemoglobin, which binds oxygen for transport.
Red blood cells are biconcave, increasing surface area for gas exchange.
Red blood cells lack a nucleus, giving more space for haemoglobin.
Platelets are cell fragments that adhere to damaged vessel walls.
Platelets clump to form a clot, preventing pathogen entry and allowing healing.

Examiner tips

  • Use the exact terms: haemoglobin, biconcave, nucleus, clump, clot
  • Show the link between structure and function for each cell type
  • Keep the answer concise and to the point

Common mistakes

  • Confusing platelets with red blood cells, or describing them as whole cells
  • Omitting the lack of nucleus in red blood cells
  • Failing to mention the protective role of clots in preventing infection

Mark scheme (5 marks)

  1. Red blood cells contain haemoglobin which carries/binds oxygen
  2. Red blood cells have a biconcave shape which increases surface area for gaseous exchange
  3. Red blood cells have no nucleus, allowing more space/volume for haemoglobin
  4. Platelets are cell fragments that stick to a broken/damaged vessel wall and clump together to block the cut
  5. Clumping of platelets forms a scab/clot which prevents pathogens entering and allows the vessel to heal

Key terms in this question

platelets · red blood cells

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