Question

Oxygen is carried from the lungs to tissues by the protein haemoglobin in red blood cells. Sickle cell anaemia is a disease resulting from abnormal haemoglobin molecules in which a valine is substituted for a single glutamic acid in normal haemoglobin. How might this substitution affect the structure of haemoglobin

Short answer

This change may affect tertiary structure of the protein and can cause reduced affinity towards oxygen binding.

Step-by-step solution

Substitution affect the structure of haemoglobin

Glutamic acid has polar side chains (usually has charge -l). Valine has a nonpolar side chain (see the picture below). Their replacement may affect tertiary structure because different intermolecular forces can occur. Therefore, the replacement may cause a change in affinity towards binding an oxygen molecule.

Hence This change may affect tertiary structure of the protein and can cause reduced affinity towards oxygen binding