Blood — Cambridge IGCSE Combined Science

The components of blood and their functions, and why blood clots: to stop blood loss and keep pathogens out.

Spec B9.4Transport in animals, subtopic 4 of 4

Revision notes

2 short notes, in the order of the specification. Each one in short:

Components of blood
Blood is made of red blood cells, white blood cells, platelets and plasma. Red blood cells have no nucleus and contain haemoglobin, which combines with oxygen to transport it. White blood cells defend against pathogens by phagocytosis and antibody production. Platelets help blood to clot, and plasma transports cells, ions, nutrients, urea, hormones and carbon dioxide.
White blood cells and blood clotting
Supplement
Lymphocytes make antibodies and phagocytes engulf pathogens; clotting converts soluble fibrinogen to insoluble fibrin, forming a mesh that seals a wound.

5 exam-style questions (11 marks), each with its mark scheme.

5 cards: flip them, mark what you knew, and practise the rest.

The whole of transport in animals on one page, so you can see where this subtopic fits.

Free PDFs to print or save.

List the four components of blood.
Show answer
Red blood cells, white blood cells, platelets and plasma.
What is the function of haemoglobin?
Show answer
To transport oxygen in the red blood cells.
Supplement State two roles of blood clotting.
Show answer
Prevents blood loss and prevents entry of pathogens.

Written and checked against the Cambridge IGCSE Combined Science (0653) specification · Updated October 2026