CO2 Transport Mechanisms in Blood

Steps:

• Identify main CO2 transport forms: dissolved in plasma (1), as bicarbonate ions (3), and bound to hemoglobin as carbaminohemoglobin (2).
• In tissues with high CO2, most CO2 enters RBCs and converts to bicarbonate via carbonic anhydrase for transport (3).
• Some CO2 binds directly to hemoglobin, forming carbaminohemoglobin, aiding removal (2).
• Dissolved CO2 (1) is minimal (~7%) and not primary for efficient transport from active tissues.

Why C is correct:

• Bicarbonate (3) and carbaminohemoglobin (2) account for ~93% of CO2 transport, essential for removing high CO2 from tissues per standard physiology.

Why the others are wrong:

• A includes dissolved CO2 (1), which is insignificant for bulk transport.
• B includes dissolved CO2 (1) but omits carbaminohemoglobin (2), missing a key method.
• D omits bicarbonate (3), the dominant transport form (~70%).

Final answer: C