Why Does Myoglobin Have a Histidine That Prevents Both O₂

Multiple Choice

Why does myoglobin have a histidine that prevents both O₂ and CO from binding perpendicularly to the heme plane?

A) This increases myoglobin's affinity for O₂.
B) This increases myoglobin's affinity for CO.
C) This lessens the difference in myoglobin's affinity for CO versus O₂.
D) This prevents the iron of the heme from being oxidized.