(a) Erythrocytes consist of a red coloured pigment called haemoglobin.
(b) Haemoglobin is a complex protein and is composed of:
(i) A protein called globin.
(ii) Fe2+ porphyrin ring called haem.
(c) Haemoglobin transports 02 in the form of ! oxyhaemoglobin from the lungs to the tissues.
(d) When oxyhaemoglobin reaches the tissue, where ! there is low oxygen pressure, oxyhaemoglobin dissociates into oxygen and deoxyhaemoglobin.
(e) C02 producing in the tissue reacts with the amine
radicals of haemoglobin and forms carbamino haemoglobin and is transported outside in this form.