Respiration is the process through which living organisms take in oxygen and give out carbon dioxide to release energy. So, naturally, a major and vital part of respiration is the gas exchange. The transport of gases during respiration, both O2 and CO2 is carried out by blood.
Transport of Oxygen during Respiration
During respiration, 97% of oxygen is transported by RBCs in blood and the remaining 3% is dissolved in the plasma. Haemoglobin is a pigment that gives blood its red colour. It is present in the RBCs. Oxygen binds with haemoglobin to form oxyhaemoglobin, which depends on the partial pressures of O2 and CO2, H+concentration and temperature. One haemoglobin molecule can carry up to 4 molecules of O2. High pO2,low pCO2, low H+ concentration and low temperature are ideal conditions for the formation of oxyhaemoglobin. These conditions are met in the alveoli. But in the tissues, opposite conditions exist and so oxygen is dissociated from the oxyhaemoglobin here. Every 100mL of blood that gets oxygenated in the lung surface can deliver 5 mL of oxygen to the tissues on an average.
Transport of Carbon Dioxide during Respiration
Around 20-25% of CO2 is carried by haemoglobin as carbamino-haemoglobin. 7% is in a dissolved state in the plasma and the remaining is carried as bicarbonate. Again, the binding of CO2 with haemoglobin is related to the pCO2, and pO2. As mentioned earlier, pCO2 is high in the tissues and this is where more binding of CO2 occurs. In the alveoli where pO2 is high, CO2 gets dissociated from carbamino-haemoglobin. The enzyme carbonic anhydrase present in a high concentration in RBCs, and in small quantities in the plasma, facilitates this reaction in both the directions. So, the bicarbonate formed at the tissues releases CO2 at the alveoli. Every 100 mL of deoxygenated blood can deliver 4 mL of CO2 to the alveoli.
To know more about the gas exchange and respiration, watch interactive videos at Byju’s- The Learning App.