Answer
Hemoglobin is a protein present in red blood cell that contains
globular chains, iron atom and heme group.
The heme group is responsible for the red colour of the
blood.
- Each hemoglobin molecule has 4 globular chains
(2 alpha and 2 beta)
- Each chain contain a heme group that serves an
oxygen binding site as it contains an iron
atom.
- Hence, oxygen has a total of four oxygen binding
sites.
- When one oxygen molecule binds to the hemoglobin, it
increases hemoglobin's affinity for oxygen and promote
binding of more molecules until maximum capacity is reached.
- Hemoglobin increases the blood capacity for oxygen for about
seventy folds.
- The oxygen transported in blood dissolved in plasma is about
3%, while the oxygen transported bound to the hemoglobin is
about 97%.
Hence, hemoglobin increases blood capacity for oxygen.