# Explain how the Krebs cycle contributes to ATP production during aerobic cell respiration.

> IB DP Biology Standard Level (2023 syllabus) — C1.2 Cell respiration · Explain · 4 marks

## Mark scheme (4 marks)

1. Acetyl coenzyme A (acetyl CoA) enters the Krebs cycle by combining with oxaloacetate to form citrate (a 6-carbon compound)
2. Carbon dioxide is released and coenzymes (NAD and FAD) are reduced / hydrogen carriers are reduced during oxidation reactions in the cycle
3. A small amount of ATP is produced directly in the Krebs cycle by substrate-level phosphorylation
4. The reduced coenzymes (NADH/FADH₂) pass electrons to the electron transport chain, driving oxidative phosphorylation and producing the majority of ATP

## Key terms

- [Krebs cycle](https://www.gradenine.co.uk/glossary/krebs-cycle)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-krebs-cycle-contributes-815fd813) · Published by Druglandscape Ltd.