The Hemoglobin Protein, Responsible for Carrying Oxygen in Red Blood

Multiple Choice

The hemoglobin protein, responsible for carrying oxygen in red blood cells, is composed of four polypeptide chains: two alpha-globin and two beta-globin. Sickle cell anemia is characterized by a mutation that causes a change in one amino acid in the beta-chain. This change substitutes a hydrophobic amino acid side chain for the normal polar side chain; therefore, these mutant chains stick to other hemoglobin molecules instead of being attracted to water molecules in the cellular environment. As a result, many hemoglobin molecules clump together, forming large fibers and sickle-shaped red blood cells that are unable to deliver needed oxygen to the body's tissues. The sickle cell mutation affects which level(s) of hemoglobin structure?

A) tertiary and quaternary only
B) primary and secondary only
C) primary plus abnormal protein aggregation
D) secondary plus abnormal protein aggregation
E) tertiary only