IGCSE Biology glossary
Haemoglobin
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Definition
A red iron-containing protein found in red blood cells that reversibly binds with oxygen to form oxyhaemoglobin in the lungs. In tissues where oxygen concentration is low, oxyhaemoglobin releases its oxygen for use in aerobic respiration.
What to include in an exam answer
The reaction is reversible: haemoglobin + oxygen forms oxyhaemoglobin in the lungs, and oxyhaemoglobin releases oxygen in the tissues. State that haemoglobin binds to oxygen, not that it 'carries' oxygen.
Example in context
Describe how haemoglobin transports oxygen (2 marks): In the lungs, haemoglobin combines with oxygen to form oxyhaemoglobin. In body tissues where oxygen concentration is low, oxyhaemoglobin dissociates, releasing oxygen for respiration.
Related syllabus topic
Transport in animals