Red Blood Cells, Haemoglobin & 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

Haemoglobin structure diagram

Molecular structure of haemoglobin Haemoglobin proteins are made up of four subunits, each of which contains a region called a haem group to which oxygen can bind

When oxygen binds to haemoglobin, oxyhaemoglobin is formed

Oxygen + Haemoglobin $⇌$ Oxyhaemoglobin

4O₂ + Hb $⇌$ Hb4O₂

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

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 1.3 cm³of oxygen.

Calculate how much oxygen can be carried in 1 dm³ of blood.

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 1.3 cm³ of oxygen

1.3 x 150 = 195

Therefore 150 g of haemoglobin can carry 195 cm³of oxygen

195 cm³is the final answer

Examiner Tip

In mathematical questions, remember that 1000 cm³ equals 1 dm³

Red Blood Cells, Haemoglobin & Oxygen (CIE AS Biology)

Revision Note