Oxyhemoglobin is formed when iron binds to which molecule?

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Multiple Choice

Oxyhemoglobin is formed when iron binds to which molecule?

Oxyhemoglobin forms when oxygen binds to iron in the heme group of hemoglobin. Each iron atom (in the ferrous Fe2+ state) can reversibly bind one O2 molecule, and with four heme units in a hemoglobin molecule, up to four oxygen molecules can be carried. This binding is what allows oxygen picked up in the lungs to be released where tissues need it. The other options don’t fit this direct iron–oxygen interaction: carbon dioxide attaches to the globin part to form carbaminohemoglobin, not to the iron; carbon monoxide can bind iron with very high affinity to form carboxyhemoglobin, blocking oxygen binding; nitrogen does not participate in forming oxyhemoglobin.

Oxyhemoglobin forms when oxygen binds to iron in the heme group of hemoglobin. Each iron atom (in the ferrous Fe2+ state) can reversibly bind one O2 molecule, and with four heme units in a hemoglobin molecule, up to four oxygen molecules can be carried. This binding is what allows oxygen picked up in the lungs to be released where tissues need it.

The other options don’t fit this direct iron–oxygen interaction: carbon dioxide attaches to the globin part to form carbaminohemoglobin, not to the iron; carbon monoxide can bind iron with very high affinity to form carboxyhemoglobin, blocking oxygen binding; nitrogen does not participate in forming oxyhemoglobin.

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