haemoglobin

• oxygen is transported via erythrocytes- red blood cells. These cells contain haemoglobin, when haemoglobin takes up oxygen it becomes oxyhaemoglobin:

  haemoglobin + oxygen > oxyhaemoglobin
• Haemoglobin is a complex protein with four subunits. each subunit consists of a polypeptide chain and a haem group. The haem group contains a single iron ion in the form of Fe 2+. This ion can attract an oxygen molecule. the haem group has a high affinity to oxygen. each haem group can hold one oxygen molecule. a red blood cell can carry over one billion oxygen molecules,