Question

Describe the jobs that red blood cells perform in moving oxygen and carbon dioxide. Include the role of hemoglobin as well as any important enzymes in red cells. Describe the movement of both gases during internal and external respiration.

Answer 1

Transportation of oxygen by blood in 2 forms -

1. Dissolved form - about 0.3ml of oxygen per 100 ml of blood per 100 mmHg is transported. Greater the arterial PO2 more amount is dissolved.

2. In combination with heamoglobin -

heamoglobin molecule has 4 heme group. It is ferrous ion ( Fe+2) . This Fe+2 combines 1 mole of oxygen. 4 Fe+2 combines 4 moles of oxygen. This is given by oxygen dissociation curve.

Transport of carbon dioxide -

In dissolved form - plasma and RBC.

In RBC - CO2 gets rapidly hydrated to give H2CO3 in the presence of enzyme called Carbonic anyhydrase. This is transported in red blood cells .

Inspiration - it is a active process. Size of thoracic cavity increases and the expansion of lung is due to fall in pressure.

Expiration - it is a passive process. It is the elastic recoil of thoracic wall and lungs