- Red blood cells carry oxygen around the body
- Haemoglobin iron that bonds with oxygen
- No nucleus – this makes room for the haemoglobin (this is called an enucleated cell)
- No mitochondria as they respire anaerobically – cells don’t use the oxygen they transport.
- Biconcave properties – (flat with a depression in the centre). This round shape allows them to pass through narrow capillaries, dip increases surface area and distance for difussion