Describe the functions of platelets and plasma in the blood.

Eduqas GCSE Biology — 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)

Platelets are small cell fragments that are essential for blood clotting; they aggregate to form a plug at a damaged vessel, preventing blood loss and blocking the entry of pathogens.
Plasma is the liquid component of blood; it transports dissolved substances such as ions, nutrients, hormones and waste products throughout the body.

Examiner tips

Use the exact terms ‘platelets’ and ‘plasma’. Show the two functions of each: clotting for platelets, transport for plasma. Keep the answer brief – 4 marks only.
Include the point that plasma is the liquid part of blood carrying cells and substances.

Common mistakes

Confusing platelets with red blood cells. Forgetting to mention that plasma carries dissolved substances. Using vague wording like ‘helps blood’ instead of specific functions.

Mark scheme (4 marks)

Platelets are involved in blood clotting / clot formation
Clotting (by platelets) prevents blood loss / prevents entry of pathogens / microorganisms
Plasma transports dissolved substances around the body
Plasma is the liquid part / component of blood (that carries cells and dissolved substances)

Key terms in this question

platelets · plasma