2 2 2 Explain The Adaptive Advantage Of Haemoglobin

Haemoglobin is a protein made up of 4 polypeptide chains, each bonded is bonded to a haem (iron) group.

Haemoglobin is able to increase the oxygen-carrying capacity of blood. Due to the fact that each haemoglobin molecule contains 4 haem units, each molecule can bond to 4 oxygen molecules at once. Hence much more oxygen can be transported around the blood in haemoglobin, rather than being dissolved in plasma.

Another advantage is that once 1 oxygen molecule binds to the haemoglobin its ability to bind more oxygen molecules increases. The bonding of each oxygen molecule slightly alters the shape of the haemoglobin, making it easier for subsequent molecules to bind to it. This increases the rate and efficiency of oxygen uptake. As a result, a small increase in oxygen concentration at the lungs results in a large increase in oxygen saturation in the blood. For example during exercise.

Another advantage is that haemoglobin’s capacity to release oxygen increases in the presence of carbon dioxide. Metabolizing cells produce carbon dioxide, which combines with water to form carbonic acid, which lowers the pH. Haemoglobin has a lower affinity for oxygen at a lower pH, as a result oxygen is released in areas where it is needed (metabolizing cells)

Once haemoglobin releases oxygen it has an increased ability to pick up carbon dioxide.

The fact that haemoglobin is enclosed inside red blood cells, means that it doesn’t disturb the osmotic balance of the blood plasma.