Transport of Gases — Prelims Strategy

Prelims Strategy

To excel in NEET questions on 'Transport of Gases', a multi-faceted strategy is recommended. Firstly, master the percentages: clearly remember the approximate percentages of oxygen transported by hemoglobin (97%) and dissolved in plasma (3%), and similarly for carbon dioxide (dissolved: 7-10%, carbaminohemoglobin: 20-25%, bicarbonate: 70%).

These are frequently tested factual recall points. Secondly, understand the oxygen-hemoglobin dissociation curve (ODC): know its sigmoidal shape and why it's important (cooperative binding). Crucially, memorize the factors that cause a 'right shift' (increased PCO\_2, decreased pH, increased temperature, increased 2,3-BPG) and a 'left shift' (opposite conditions).

Visualize these shifts and their physiological implications (right shift for O\_2 unloading in tissues, left shift for O\_2 loading in lungs). Thirdly, comprehend CO\_2 transport mechanisms: focus on the role of carbonic anhydrase, the formation of bicarbonate ions, and the detailed steps of the chloride shift (including its reversal in the lungs).

Fourthly, differentiate between Bohr and Haldane effects: understand that Bohr effect is about CO\_2/H\_ + affecting O\_2 affinity, while Haldane effect is about O\_2 affecting CO\_2/H\_ + affinity.

Finally, practice numerical problems related to partial pressures and conceptual questions involving clinical scenarios like CO poisoning or high-altitude adaptation. Pay close attention to trap options that often swap conditions for right/left shifts or confuse the effects.