The Role of Haemoglobin (AQA AS Biology): Revision Note
Exam code: 7401
Haemoglobin & red blood cells
Red blood cells
Red blood cells have a specialised structure that maximises their ability to transport oxygen:
They have no nucleus to maximise the space available for haemoglobin
They have a biconcave shape to maximise the surface area for the diffusion of oxygen
They are highly flexible to allow them to pass through narrow capillaries
Their diameter is approximately the same as that of the capillaries, slowing down the flow of blood to maximise time for diffusion
Haemoglobin
Haemoglobin is located within red blood cells, where its role is to transport oxygen around the body
When oxygen binds to haemoglobin, oxyhaemoglobin is formed:
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oxyhaemoglobin
4O2 + Hb Hb4O 2
Each molecule of haemoglobin contains four haem groups, each able to bond with a single molecule of oxygen (O2)
Each molecule of haemoglobin can carry four oxygen molecules, or eight oxygen atoms
Worked Example
There is around 150 g of haemoglobin in 1 dm3 of blood.
In a healthy adult at room temperature, 1 g of haemoglobin can combine with 1.4 cm3 of oxygen.
Calculate how much oxygen can be carried in 1 dm3 of blood.
Answer:
Step one: identify the relevant information from the question
In 1 dm3 of blood, there is 150 g of haemoglobin
1 g of haemoglobin can carry 1.4 cm3 of oxygen
Step two: find the scale factor between 1 g and 150 g
150 ÷ 1 = 150
Step three: multiply the volume of oxygen carried by the scale factor
1.4 x 150 = 210 cm3
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