The iron ion Fe2+ in the heme group of myoglobin has a coordination number of 6, which means it is bonded to six neighboring atoms. The geometry of this coordination is octahedral.In the heme group, four of the six coordination sites are occupied by nitrogen atoms from the porphyrin ring. The fifth coordination site is occupied by a nitrogen atom from the imidazole side chain of a histidine residue in the myoglobin protein. This histidine residue is often referred to as the proximal histidine. The sixth coordination site is available for binding to other molecules, such as oxygen O2 .The coordination of the iron ion in the heme group contributes to the function of myoglobin as an oxygen carrier in the body in several ways:1. The octahedral geometry allows for the reversible binding of oxygen to the iron ion. When oxygen binds to the iron ion, it forms a coordinate covalent bond, which can be easily broken when oxygen needs to be released.2. The coordination of the iron ion to the histidine residue helps to stabilize the binding of oxygen. The histidine residue also prevents the iron ion from being oxidized to its ferric state Fe3+ , which would not be able to bind oxygen.3. The coordination of the iron ion to the nitrogen atoms in the porphyrin ring helps to fine-tune the binding affinity of myoglobin for oxygen. This allows myoglobin to effectively bind and release oxygen in response to changes in oxygen concentration in the body.Overall, the coordination of the iron ion in the heme group of myoglobin plays a crucial role in its function as an oxygen carrier in the body.