KALLISTA IMAGES / CUSTOM MEDICAL STOCK PHOTO / SCIENCE PHOTO LIBRARY KALLISTA IMAGES / CUSTOM MEDICAL STOCK PHOTO / SCIENCE PHOTO LIBRARY
Oxygenated haemoglobin. Computer model of haemoglobin, the principal protein component of red blood cells. Each molecule is made up of four subunits (coloured ribbon structures) called alpha and beta subunits. Within each subunit is an oxygen binding site, or haem group (turquoise). Each haem group contains one atom of iron (green). In this model, the haem groups of the hemoglobin are oxygenated, with oxygen molecules shown as paired red spheres associated with the iron. Haemoglobin transports oxygen around the body by binding one oxygen molecule to each haem group. This means that each molecule of haemoglobin can transport four molecules of oxygen. The oxygen is released to the tissues and the haemoglobin returns to its deoxygenated form.
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