Explain how plasma and platelets each carry out their functions in the blood.

Edexcel GCSE Biology (1BI0) — 8.2 Transport in animals (blood and circulation) · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Plasma is a yellow liquid that transports substances around the body.
Plasma carries nutrients, hormones, proteins, waste products such as urea, dissolved gases and antibodies.
Platelets are small fragments of cells that are involved in blood clotting.
By forming clots platelets prevent pathogens from entering the body and stop excessive blood loss.

Examiner tips

  • Use the exact terms ‘plasma’, ‘platelets’, ‘clotting’
  • Show the two functions of each component
  • Keep the answer concise and to the point

Common mistakes

  • Confusing platelets with red blood cells
  • Omitting the role of plasma in transporting dissolved gases
  • Using vague language such as ‘carry stuff’ instead of specific substances

Mark scheme (4 marks)

  1. Plasma is a yellow liquid / fluid that transports substances around the body
  2. Plasma carries named substances such as nutrients, hormones, proteins, waste products (e.g. urea), dissolved gases or antibodies
  3. Platelets are small fragments of cells involved in blood clotting
  4. Blood clotting by platelets prevents pathogens entering the body / prevents excessive blood loss

Key terms in this question

plasma · platelets

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