Transport of Gases — Prelims Strategy

Prelims Strategy

To effectively tackle NEET questions on the transport of gases, a multi-pronged strategy is recommended. Firstly, memorize the percentage contributions of different forms of transport for both oxygen (97% oxyhaemoglobin, 3% dissolved) and carbon dioxide (70% bicarbonate, 20-25% carbamino-haemoglobin, 7-10% dissolved).

Secondly, develop a deep conceptual understanding of the oxygen-haemoglobin dissociation curve: its sigmoid shape, the factors that cause a right shift (increased $P_{CO_2}$, increased H$^+$/decreased pH, increased temperature, increased 2,3-BPG), and a left shift (opposite conditions).

Relate these shifts to physiological needs in tissues versus lungs. Thirdly, understand the specific roles of key players: haemoglobin (for both O\_2 and CO\_2), carbonic anhydrase (for CO\_2 hydration), and the Chloride Shift mechanism (for electrical neutrality).

Finally, differentiate clearly between the Bohr effect (CO\_2/H$^+$ on O\_2 affinity) and the Haldane effect (O\_2 on CO\_2/H$^+$ affinity), as these are frequently confused. For numerical problems, though rare, ensure you understand partial pressure gradients.

Practice identifying trap options, which often involve mixing up conditions for right/left shifts or confusing the names of different effects.