Explain how red blood cells are adapted to carry oxygen.

Firstly, red blood cells contain the globular protein haemoglobin which is able to bind reversibly with oxygen. This means red blood cells can take up and then release oxygen as they transport it around the body. Secondly, there is no nucleus in a red blood cell, meaning that more haemoglobin can fit in the blood cell and lastly, it has a biconcave shape. This increases the surface area of the cell and means more oxygen can pass through it.