Which of the Following Explains Why the Ferrous Ion Is

Multiple Choice

Which of the following explains why the ferrous ion is not oxidized to the ferric state in the globin proteins even though free heme in solution is readily oxidized?

A) when bound to globins, the heme is always planar; when free in solution, heme adopts a non-planar configuration which allows the oxidation of the iron
B) the globin proteins provide a hydrophobic environment that prevents oxidation
C) coordination with the proximal histidine allows any oxidized iron to be rapidly reduced back to the ferrous state
D) since the oxygen is hydrogen bound to the distal histidine, if oxidation of iron does occur, the distal histidine allows for rapid reduction
E) none of the above