# Explain how the structure of a red blood cell is adapted to its function in transporting oxygen.

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

## Mark scheme (4 marks)

1. Biconcave disc shape increases the surface area to volume ratio
2. Large surface area to volume ratio allows faster diffusion of oxygen into and out of the cell
3. Absence of a nucleus (and most organelles) provides more space for haemoglobin
4. Haemoglobin binds oxygen / forms oxyhaemoglobin, enabling efficient oxygen transport in the blood

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