Forms of CO₂ Transport in Blood
CO₂ is carried in three main forms:
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Dissolved CO₂: About 5–10% of total CO₂ is simply dissolved in plasma. This fraction is directly proportional to the partial pressure of CO₂ (PaCO₂).
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Carbamino compounds: ~20–30% of CO₂ binds to amino groups of hemoglobin (Hb) and plasma proteins, forming carbaminohemoglobin. Binding is favored in deoxygenated blood (Haldane effect).
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Bicarbonate ions (HCO₃⁻): The majority (~60–70%) is transported as bicarbonate. This is formed via the reaction:
CO2+H2O→carbonic anhydraseH2CO3→H++HCO3−CO₂ + H₂O \xrightarrow{\text{carbonic anhydrase}} H₂CO₃ \rightarrow H⁺ + HCO₃⁻
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