Haemoglobin

In the syllabus and the exam

Haemoglobin links the structure of red blood cells to the function of oxygen transport, and exam questions typically ask candidates to explain both how it picks up oxygen and why red blood cells are adapted to carry it efficiently. Candidates should be able to state that haemoglobin combines reversibly with oxygen to form oxyhaemoglobin in regions of high oxygen concentration such as the alveoli, and releases oxygen again in regions of low oxygen concentration such as respiring muscle tissue, so the binding is described as reversible rather than permanent. This term also connects to red blood cell adaptations, since candidates are expected to explain that a biconcave shape increases surface area for gas exchange and the absence of a nucleus leaves more internal space for haemoglobin, allowing each cell to carry more oxygen. A common factual slip is describing haemoglobin as containing oxygen as a fixed component, rather than describing an association that forms and breaks depending on surrounding oxygen concentration.

Example

Haemoglobin in red blood cells binds oxygen in the lungs, where oxygen concentration is high, and releases it in respiring tissues, where concentration is low.

Related terms

ArteryGaseous exchangeDouble circulation

Source:SRC-DSKP-EN