Explain how plasma transports substances around the body, giving three examples of substances it carries.

Cambridge International IGCSE Biology (0610) — 9.4 Blood · 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 the yellow liquid component of blood that carries substances in solution or in suspension.

1. Glucose – a small molecule dissolved in plasma.
2. Hormones – for example insulin, carried in plasma to target tissues.
3. Antibodies – e.g. IgG, transported in plasma to sites of infection.

Examiner tips

Use the term ‘plasma’ and describe it as a liquid component. Give three distinct substances – a small molecule, a hormone and a protein. Show the substances are carried in solution or suspension.

Common mistakes

Using the wrong word for plasma (e.g. ‘serum’). Listing the same type of substance twice. Failing to mention that plasma is a liquid component of blood.

Mark scheme (4 marks)

Plasma is a yellow liquid / liquid component of blood that carries substances in solution (or in suspension)
First named substance correctly identified as one carried by plasma
Second named substance correctly identified as one carried by plasma (different from first)
Third named substance correctly identified as one carried by plasma (different from first two)

Key terms in this question

plasma