Iron. In the blood, the red substance, haemoglobin, is found in red blood corpuscles. This haemoglobin is a protein whose use is to transport oxygen round the body (obtained from the lungs) to the cells that need it, and waste carbon dioxide from the cells that need to get rid of it, which it transports back to the lungs for us to breathe out. Haemoglobin molecules contain an atom of the metal iron at the centre. So if you are anaemic, this is because you do not have enough haemoglobin - usually as a result of iron deficiency.