In: Biology
Which of the following is a form of hemoglobin in which iron is in the Fe+3 state and can be reduced back to a Fe+2 state by a RBC pathway?
a. Sulfhemoglobin
b. Deoxyhemoglobin
c. Oxyhemoglobin
d. methemoglobin
The answer is methemoglogin (d)
Methemoglobin is a form of oxygen-carrying metalloprotein hemoglobin in which the iron in the form of Fe+3. Methemoglobin cannot bind oxygen, unlike oxyhemoglobin. In the human blood trace amount of methemoglobin is normally produced spontaneously. The NADH-dependent enzyme methemoglobin reductase converts methemogloin back to hemoglobin, which will bind iron in the form of Fe+2. The presence of methemoglobin causes a disorder known methemoglobinemia, which the iron in the form of Fe+3 and has decreased capacity to bind oxygen. This will lead to an overall reduced ability of red blood cells to release oxygen to tissues.