The largest fraction of carbon dioxide transported in arterial blood is carried as:

• A Carbamino compounds with haemoglobin
• B Carbonic acid bound to plasma proteins
• C Physically dissolved carbon dioxide
• D Bicarbonate ions in plasma and red cells ✓

Explanation

About 70% of transported CO2 travels as bicarbonate, generated inside the red cell by carbonic anhydrase and exported via the chloride shift. Roughly 20 to 23% rides as carbamino compounds, chiefly on the globin chains of deoxyhaemoglobin, and only 7 to 10% is physically dissolved despite CO2 being far more soluble than oxygen. Deoxygenated haemoglobin buffers hydrogen ions, linking transport to the Haldane effect.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.