BMAT Biology Practice: Part 2

An advanced, interactive quiz on The Workhorses of the Cell: Proteins & Enzymes.

Problem 11: The Sickle-Cell Substitution

Hard
ProteinsGeneticsStructure-FunctionDisease

In sickle-cell anemia, a single point mutation in the gene for the β-globin chain of hemoglobin results in the substitution of valine for glutamic acid at the 6th position. Why does this single change have such a catastrophic effect on the protein's function?

A

Valine is much larger than glutamic acid, physically distorting the entire hemoglobin molecule.

B

Glutamic acid is acidic (negatively charged), while valine is hydrophobic; this change promotes aggregation of hemoglobin molecules in low-oxygen conditions.

C

The mutation breaks a critical disulfide bridge necessary for hemoglobin's quaternary structure.

D

The substitution occurs in the enzyme's active site, preventing oxygen from binding.