# Explain why a cell with a large number of mitochondria and an extensively folded inner mitochondrial membrane is likely to be metabolically very active.

> OCR A-Level Biology A (H420) — 2.1 Cell structure · Explain · 4 marks

> Cardiac muscle cells contain far more mitochondria per cell than most other cell types in the human body. The inner membrane of each mitochondrion is folded into numerous cristae.

## Mark scheme (4 marks)

1. A large number of mitochondria increases the total capacity for aerobic respiration
2. Folding of the inner membrane increases the surface area available
3. Greater surface area of the inner membrane allows more ATP synthase / electron carriers to be embedded
4. Therefore more ATP is synthesised per unit time, supporting a high level of metabolic activity

## Key terms

- [mitochondria](https://www.gradenine.co.uk/glossary/mitochondria)
- [inner mitochondrial membrane](https://www.gradenine.co.uk/glossary/inner-mitochondrial-membrane)

## Related

- [Revision notes for OCR A-Level Biology A (H420)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-a-cell-with-a-6c5533cc) · Published by Druglandscape Ltd.