A typical example is hemoglobin,
which is formed by 4 globin subunits:
beta1 and beta2.
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Each globin subunit has an heme
group bound (a protoporphyrin IX molecule complexed with an Fe2+ ion), which gives hemoglobin and blood their red color.
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1) for a close view of a
Let's put the iron atom in its
In the lungs, where oxygen is abundant, an oxygen molecule
Fe2+ in each heme group. Later, it will be released in the tissues, where oxygen is needed for metabolism.
4) Iron is also bound to the N in the sidechain of an histidine