Answer:Heme, ferrous state (Fe 2+ )
Explanation:
Heme is a coordination complex which consists of an iron ion coordinated to a porphyrin acting as a tetradentate ligand, and to one or two axial ligands.
Four heme groups makes up each haemoglobin and they surround the globin group to form a tetrahedral structure. Heme composes of a ringlike organic compound known as a porphyrin to which an iron atom is attached. The four iron atoms in each haemoglobin binds with four atom of oxygen as the blood travels between the lungs. During Digestion and absorption, Iron ions undergo two changes of oxidation state.
The first, occurs in the stomach, where Iron (III) is reduced to iron (II)
and the second occurs in the duodenum where free iron (II) ions are oxidized to iron (III).
Myoglobin also contains hemes, which makes colour of red meat. The colour that meat assumes is partly determined by the degree of oxidation of the myoglobin. Most times the oxidation state is in the ferrous state.
