State the defence functions of white blood cells
Distinguish engulfing pathogens from producing antibodies.
Section 9.4 · Blood
Exam scope and assessment notes
Core and Extended · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall red/white-cell identification.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is a pathogen in this context?
What you will learn
- White cells defend by different mechanisms
- Match a function to supplied evidence
White cells defend by different mechanisms
White blood cells contribute to defence against pathogens, organisms or agents that cause disease. Some engulf pathogens by phagocytosis. Others produce antibodies that act against specific antigens. These are distinct functions within the broad white-cell category; one vague statement such as “they clean blood” does not describe either.
Core practice needs both phagocytosis and antibody production. Extended lessons identify the phagocyte and lymphocyte categories and examine their mechanisms more closely. Do not say every white blood cell always performs both functions in the same way.
Match a function to supplied evidence
If a sequence shows a white cell surrounding and taking a pathogen inside, that supports phagocytosis. If evidence states production of a specific binding protein, that supports antibody production. The white cell’s general appearance alone does not show what it is doing at that instant.
Red cells mainly carry oxygen and platelets contribute to clotting; these should not be reassigned antibody production just because they are also in blood. Defence is a biological explanation here, not a guarantee that every exposure is prevented or a medical recommendation about an individual infection.
Pause and explain
Which pair names two white-cell defence functions?
Worked example
A white cell encloses a pathogen; another produces a specific binding protein. State the two defence functions.
Show the worked solution
- Enclosing and taking in the pathogen is phagocytosis.
- The specific protein is an antibody.
Answer Phagocytosis and antibody production are two white-blood-cell defence functions.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State two functions of white blood cells in defence.
Give me a hint
Use one engulfing mechanism and one protein-production mechanism.
Compare my reasoning
- Phagocytosis engulfs pathogens.
- Antibody production supports specific defence.
Phagocytosis and production of antibodies.
Look for these in your work
- Include phagocytosis
- Include antibodies
A supplied sequence shows a pathogen becoming enclosed inside a white cell. Name the process.
Give me a hint
The cell takes the pathogen inside.
Compare my reasoning
- The membrane surrounds the pathogen.
- It becomes internalised in the cell.
Phagocytosis.
Look for these in your work
- Name the process
- Use engulfing evidence
Improve “red cells defend us by making antibodies; all white cells just transport oxygen”.
Give me a hint
Reassign the functions to the correct categories.
Compare my reasoning
- Red cells transport oxygen with haemoglobin.
- White cells provide defence by phagocytosis and antibody production.
Red cells transport oxygen; white blood cells contribute to defence through phagocytosis and antibody production.
Look for these in your work
- Correct red-cell function
- Include both white-cell functions
Common mistakes
- Assigning antibody production to platelets.
- Saying all white cells perform identical roles.
What can you explain now?
Which pair names two white-cell defence functions?
Compare with the explanation
Phagocytosis and antibody production
Both required functions are included.
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Make it stick
Explain two different defence functions without assigning them to red cells.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.