Simulation · Biology · Class 11
How blood carries carbon dioxide
From the lesson Transport of carbon dioxide in Breathing and Exchange of Gases. Change the values and watch what happens.
How blood carries carbon dioxideBiology · Class 11
The idea behind it
NCERT §14.4, §14.4.2
- Roughly 70 per cent of CO₂ travels as bicarbonate, about 20–25 per cent is bound to haemoglobin as carbamino-haemoglobin, and about 7 per cent is dissolved in plasma.
- CO₂ binding to haemoglobin depends on pCO₂, with pO₂ also a major influence. In the tissues, high pCO₂ and low pO₂ favour more CO₂ binding; in the alveoli, low pCO₂ and high pO₂ make CO₂ dissociate from carbamino-haemoglobin.
- The enzyme carbonic anhydrase is present at very high concentration in RBCs, and in minute amounts in plasma as well.
- Carbonic anhydrase speeds up both directions of the reaction CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺.
- In the tissues, catabolism raises pCO₂, so CO₂ diffuses into the blood (both RBCs and plasma), where HCO₃⁻ and H⁺ are formed.
- At the alveoli, where pCO₂ is low, the reaction runs the other way, giving back CO₂ and H₂O. CO₂ trapped as bicarbonate at the tissues is thus released at the alveoli.
- Every 100 mL of deoxygenated blood delivers roughly 4 mL of CO₂ to the alveoli.