Your questions is alot like asking why for example the atmosphere requires ozone. True it's properties affect the way sunlight enters the earth, and therefore life on earth, but it has an implicit "chicken or the egg" conundrum quality. The answer to "What is Iron's role in Haemoglobin's oxygen transport capabilities?", is related to Irons valency (Outer electrons, different oxidation states and energy setups)and the way it takes up and releases oxygen under different oxygen concentrations (when it is associated with the rest of the protien.
Oxygen
Carbon monoxide (CO) interferes with oxygen transport by binding to hemoglobin more strongly than oxygen, forming carboxyhemoglobin. This reduces the oxygen-carrying capacity of the blood and can lead to oxygen deprivation in the body's tissues.
Hemoglobin transports gasses around the body. Hemoglobin contains iron and other minerals. It forms HbO8 and HbCO2 when bond with gasses.
You have Iron atoms in hemoglobin. This atom is the binding site for oxygen in case of hemoglobin.
This is not the main reason:The molecular mass of CO is 28 a.m.u while that of O2 is 32 a.m.u therefore the rate of diffusion of CO is higher than O2 and it enter fast into respiratory track and lungs and causes the deficiency of oxygen.Added:(The more important reason is):CO is about 200 times more reactive to 'ferro'-hemoglobin than O2, so it can hardly be replaced by the available excess of oxygen in air, thus preventing the life-essential O2-transfer to parts of the body like brains and hart & lung muscles.(Cf. 'Related links' down this answering page)
The bond between oxygen and hemoglobin is a reversible coordination bond formed between the iron atom in the heme group of hemoglobin and the oxygen molecule. This bond allows hemoglobin to transport oxygen from the lungs to tissues throughout the body.
The rise of temperature denatures the bond between oxygen and hemoglobin.
CO
Hemoglobin contains iron atoms that bind to oxygen molecules. This iron atom within the heme group forms a reversible bond with oxygen, allowing hemoglobin to efficiently transport oxygen throughout the body.
Oxygen
Carbon monoxide (CO) interferes with oxygen transport by binding to hemoglobin more strongly than oxygen, forming carboxyhemoglobin. This reduces the oxygen-carrying capacity of the blood and can lead to oxygen deprivation in the body's tissues.
The heme group within the hemoglobin molecule is what actually binds to the oxygen molecule. This process involves the iron atom within the heme group forming a reversible coordination bond with the oxygen molecule.
hemoglobin
Oxygen in the blood is transported by hemoglobin.
there is an inability for Oxygen to properly bond to the Hemoglobin molecules in the damaged cell
With the Bohr effect, more oxygen is released in tissues that are actively metabolizing due to a decrease in pH. This decrease in pH reduces the affinity of hemoglobin for oxygen, allowing it to release more oxygen to the metabolizing cells.
Hemoglobin transports gasses around the body. Hemoglobin contains iron and other minerals. It forms HbO8 and HbCO2 when bond with gasses.