# Explain how the structure of a red blood cell (erythrocyte) is adapted for the transport of oxygen in mammals.

> IB DP Biology Standard Level (2023 syllabus) — B2.3 Cell specialisation · Explain · 4 marks

## Mark scheme (4 marks)

1. Biconcave disc shape increases the surface area to volume ratio, allowing more rapid diffusion of oxygen into and out of the cell.
2. Lack of a nucleus (anucleate) provides more intracellular space for haemoglobin, maximising oxygen-carrying capacity.
3. High concentration of haemoglobin in the cytoplasm enables binding and transport of oxygen molecules.
4. Flexible plasma membrane allows the cell to deform and pass through narrow capillaries, maintaining efficient oxygen delivery to tissues.

## Key terms

- [erythrocyte](https://www.gradenine.co.uk/glossary/erythrocyte)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-a-efd44b04) · Published by Druglandscape Ltd.