Red Blood Cell

What is Red Blood Cell?

A red blood cell is the cell that transports oxygen in the blood. It is a biconcave disc, thinner in the middle than at the edges, and a mature red blood cell has no nucleus, which leaves more room for haemoglobin. Haemoglobin combines with oxygen in the lungs, where the oxygen concentration is high, and releases it in respiring tissues, where the oxygen concentration is low. The cell is flexible enough to squeeze through capillaries only one cell wide.

This definition is part of the Transport in Humans chapter in Cambridge O Level Biology.

Concepts related to Red Blood Cell

• haemoglobin
• Diffusion
• Capillary

Common mistakes with Red Blood Cell

• “Red blood cells leave the capillary to form tissue fluid.” Why wrongThey are far too large to pass through the wall, which is why tissue fluid is not red. WriteTissue fluid is formed from plasma: water and small dissolved substances are forced out, while red blood cells and large plasma proteins remain in the capillary.