medium · MCAT bio-biochem

In sickle cell disease, a single missense mutation results in the substitution of a hydrophobic Valine for a hydrophilic Glutamate on the surface of the hemoglobin molecule.

Why does this cause the hemoglobin to polymerize into fibers under low-oxygen conditions?

  1. The mutation creates new disulfide bridges between hemoglobin subunits.
  2. The loss of the negative charge on Glutamate prevents the molecules from repelling each other.
  3. The Valine residue catalyzes a covalent cross-linking reaction.
  4. The hydrophobic Valine associates with other hydrophobic patches on adjacent molecules.

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