# Explain how the Bohr shift enables active tissues to obtain more oxygen from haemoglobin during periods of high metabolic activity.

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

## Mark scheme (4 marks)

1. Active tissues produce more carbon dioxide (and lactic acid), lowering the local pH / increasing CO₂ concentration.
2. Lower pH (higher H⁺ / CO₂) causes haemoglobin to change shape / reduces haemoglobin's affinity for oxygen.
3. The oxygen dissociation curve shifts to the right, meaning haemoglobin releases / unloads oxygen at a higher partial pressure of O₂ than it otherwise would.
4. This ensures that more oxygen is delivered to (unloaded at) the active tissues where it is most needed for aerobic respiration.

## Key terms

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

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-bohr-shift-enables-724693b3) · Published by Druglandscape Ltd.