The Role of Haemoglobin (AQA A Level Biology)

Transport of oxygen

• The majority of oxygen transported around the body is bound to the protein haemoglobin in red blood cells
  • Red blood cells are also known as erythrocytes
• Each molecule of haemoglobin contains four haem groups, each able to bond with one molecule of oxygen
  • This means that each molecule of haemoglobin can carry four oxygen molecules, or eight oxygen atoms in total

• When oxygen binds to haemoglobin, oxyhaemoglobin is formed

Oxygen + Haemoglobin  Oxyhaemoglobin

4O₂ + Hb  Hb4O ₂

• The binding of the first oxygen molecule results in a conformational change in the structure of the haemoglobin molecule, making it easier for each successive oxygen molecule to bind; this is cooperative binding
• The reverse of this process happens when oxygen dissociates in the tissues

To answer this question, we must look at the information already given to us in the question. You do not need prior knowledge to gain full marks here.

In 1 dm³ of blood, there is 150 g of haemoglobin.

1 g of haemoglobin can carry 1.4 cm³ of oxygen.

Step One: Find the scale factor between 1g and 150g

150g ÷ 1g = 150

Scale factor = 150

Step Two: Multiply the volume of oxygen carried by the scale factor

1.4 cm³ x 150 = 210 cm³

Therefore 150 g of haemoglobin can carry 210 cm³ of oxygen.

210 cm³ is the final answer.