[Campbell Biology P.131] Based on Figure 5.19 and the accompanying text, which of the follow... | Practice Question

Based on Figure 5.19 and the accompanying text, which of the following statements accurately describes a difference between normal hemoglobin and sickle-cell hemoglobin?

  • A: Normal hemoglobin proteins aggregate into fibers, while sickle-cell hemoglobin proteins do not.
  • B: Sickle-cell hemoglobin has a reduced capacity to carry oxygen due to aggregation, unlike normal hemoglobin.
  • C: Normal red blood cells are sickle-shaped, whereas sickle-cell red blood cells are disk-shaped.
  • D: Only sickle-cell hemoglobin exhibits a quaternary structure.

Explanation

Normal hemoglobin proteins do not associate with one another and efficiently carry oxygen, resulting in disk-shaped red blood cells. In contrast, sickle-cell hemoglobin proteins aggregate into long fibers due to hydrophobic interactions, which severely reduces their oxygen-carrying capacity and deforms the red blood cells into a sickle shape.