Explain why mitochondria are found in large numbers in sperm cells.

WJEC GCSE Biology (Wales) — 1.1.1 Cell structure and organisation · Explain · 4 marks · View as Markdown

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

Sperm cells must swim long distances through the female reproductive tract to reach and fertilise an egg cell.

Model answer (4 marks)

Mitochondria are the site of aerobic respiration, which releases energy in the form of ATP.
The ATP produced is required for the tail or flagellum to beat and propel the sperm.
Because sperm must swim long distances, a large number of mitochondria are present to supply enough ATP for sustained, long‑distance swimming.

Examiner tips

Use the term ‘aerobic respiration’ and ‘ATP’ – these are key phrases. Explain the link between ATP and flagellar motion. Mention the need for sustained energy to justify the large number of mitochondria.

Common mistakes

Saying mitochondria are ‘just’ energy factories without linking to ATP. Forgetting to mention the flagellum or swimming. Using vague terms like ‘energy’ without specifying ATP or respiration.

Mark scheme (4 marks)

Mitochondria are the site of (aerobic) respiration
Respiration releases energy (in the form of ATP)
The energy is needed for the tail/flagellum to move / for swimming
Large numbers of mitochondria provide sufficient energy for sustained/long-distance swimming

Key terms in this question

mitochondria