Why is oxyhaemoglobin important?

It is the blood molecule that carries oxygen around the body to be used in , say the muscles.

It discharges the oxygen at the point of usagem and 'picks up' carbon dioxide, to become 'carboxyhaemaglobin', which goes to the lungs and is exchanged into the air.

This molecule does NOT work without iron in oxidation state (III) ; the red colour of blood;. People with a shortage of iron in their blood stream are 'Anaemic', and often show tiredness or difficulty in breathing.

You ingest iron in your diet as red meat , when iron is in oxidation state (III), or a green vegetables , when iron is in oxidation state (II). The human organism then proceeds to oxidise Iron(II) to iron(III).

The iron ion has a porphyrin ring around it, and this porphyrin ring has various branches and functional groups attached, in order to transport oxygen and carbon dioxide. The whole is a balanced movement of electrons through this very large molecule, but it does NOT occur without the iron ion (Fe^(3+) being at the centre of things.

So (carb)oxyhaemaglobin is a very important molecule in the body, and needed to keep you alive.