BRAINCAKEHaemoglobin and Oxygen Transport
Most oxygen is carried in the blood bound to haemoglobin (Hb) in erythrocytes. Only about 1.5% travels dissolved in plasma, because oxygen is not very soluble in water.
Haemoglobin is a globular protein with a quaternary structure. Each molecule is made of four polypeptide chains: two α-globin and two β-globin chains. Each chain is attached to a haem group, a prosthetic group containing an iron ion (Fe2+). Each haem group can bind reversibly to one oxygen molecule, so one haemoglobin molecule can carry up to four oxygen molecules (eight oxygen atoms).
Hb + 4O2 ⇌ HbO8
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Key terms in this lesson
- quaternary structure
- The structure formed when two or more polypeptide chains are held together to make one functional protein.
- prosthetic group
- A non-protein group permanently bound to a protein and essential for its function, such as the haem group in haemoglobin.
More in Circulatory Systems
- Leucocytes
- Granulocytes
- Agranulocytes
- Platelets
- Oxygen Dissociation Curve for Haemoglobin
- The Bohr Effect
- Fetal Haemoglobin
- Myoglobin
All 33 lessons in Circulatory Systems · All Edexcel AS-level Biology topics