Describe the functions of plasma in the human circulatory system.

WJEC GCSE Biology (Wales) — 1.4.1 Blood and circulation · Describe · 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 liquid part of blood, mainly water, which carries cells and platelets. It transports dissolved substances such as glucose, amino acids, urea, hormones and carbon dioxide. It also carries heat energy around the body and moves waste products from the liver and other organs to the kidneys for excretion.

Examiner tips

Use the word "plasma" and mention it is the liquid component of blood.
List the key substances it transports – glucose, amino acids, urea, hormones, CO₂ – and note heat transport.
Show that it carries waste to the kidneys for excretion.
Keep the answer concise and use correct terminology.

Common mistakes

Confusing plasma with whole blood or red cells.
Omitting the transport of waste products or heat.
Using vague terms like "fluid" without specifying it is plasma.

Mark scheme (4 marks)

Plasma transports dissolved substances / named substance (e.g. glucose, amino acids, urea, hormones, carbon dioxide)
Plasma transports heat energy around the body
Plasma is the liquid component / mainly water / a fluid that carries cells and platelets
Plasma transports waste products (e.g. urea) from the liver / organs to the kidneys for excretion

Key terms in this question

plasma