Question

Explain how the change of a single amino acid in hemoglobin leads to the aggregation of hemoglobin into long fibers. (Review Figures.5.14, 5.18 and 5.19)

Short answer

The change of amino acids in hemoglobin to the aggregation of hemoglobin into long fibers is due to the non-polar condition of the particular amino acid. In this condition, the glutamine is substituted with valine which affects the functioning of the hemoglobin protein.

Step-by-step solution

Description of hemoglobin

Hemoglobin is the protein substance that contains an iron part. This substance is primarily responsible for carrying oxygen in it. The oxygen is transported to the cells, and carbon dioxide is collected from the different organs and passed to the lungs for exhalation.

Description of the protein structure of hemoglobin

There are four peptide chains present in the hemoglobin molecules that consist of more than 140 amino acids. There are two alpha chains and two beta chains present in the four branches of the hemoglobin chain.

Aggregation of hemoglobin

Glutamic acid is the sixth amino acid present in normal hemoglobin, has a negative charge in its side chain. Valine is the amino acid that is substituted in the place of glutamic acid.

Valine possesses non-polar amino acids in its side chain. It makes the hemoglobin protein get aggregated to form long fibers and destroys the normal functioning of the hemoglobin.

Hence, the substitution of valine instead of glutamic can result in the deterioration of the function of hemoglobin, causing a condition known as sickle cell anemia.