# Explain how the Bohr effect enables efficient delivery of oxygen to actively respiring tissues.

> IB DP Biology Standard Level (2023 syllabus) — B3.2 Transport · Explain · 4 marks

## Mark scheme (4 marks)

1. Actively respiring tissues produce more carbon dioxide, lowering local pH (increasing acidity).
2. Lower pH (higher H⁺ concentration) causes haemoglobin to have a reduced affinity for oxygen.
3. The oxygen–haemoglobin dissociation curve shifts to the right, meaning more oxygen is unloaded at any given partial pressure of oxygen.
4. This ensures that tissues with the highest metabolic demand receive the most oxygen, matching oxygen supply to demand.

## Key terms

- [Bohr effect](https://www.gradenine.co.uk/glossary/bohr-effect)

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-bohr-effect-enables-7b220409) · Published by Druglandscape Ltd.