Explain how memory cells protect the body more effectively when the same pathogen enters the body for a second time.

WJEC A-Level Biology (Wales) — 3.4 Population size and ecosystems · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

When a person recovers from an infection, a small number of white blood cells remain in the body as memory cells. These memory cells can provide long-lasting protection against the same pathogen.

Model answer (5 marks)

Memory cells remain in the body after the first infection and are long‑lasting. When the same pathogen enters again they recognise the specific antigen. They then divide rapidly, producing large numbers of antibody‑producing cells much faster than during the first infection. Consequently large quantities of the specific antibody are produced quickly, destroying the pathogen before symptoms develop and the person does not become ill.

Examiner tips

Mention that memory cells are long‑lasting and recognise the antigen
Explain rapid division and quick antibody production
Show the link to prevention of symptoms

Common mistakes

Failing to state that memory cells are long‑lasting
Confusing memory cells with other immune cells
Not linking rapid antibody production to prevention of illness

Mark scheme (5 marks)

Memory cells remain in the body after the first infection / are long-lasting
Memory cells recognise the same antigen / pathogen when it enters the body again
Memory cells divide rapidly / more quickly than during the first infection
Large quantities of the specific antibody are produced more quickly
The pathogen is destroyed before symptoms develop / the person does not become ill

Key terms in this question

memory cell · pathogen