How is most carbon dioxide in systemic capillaries transported?

How is most carbon dioxide in systemic capillaries transported?

• A. As carbamino compounds
• B. Combined with hemoglobin
• C. Combined with water
• D. As dissolved gas

Answer: (C)

Most carbon dioxide in systemic capillaries is primarily transported in plasma as bicarbonate ions, which are formed when carbon dioxide combines with water. This reaction is catalyzed by the enzyme carbonic anhydrase, leading to the formation of carbonic acid, which quickly dissociates into bicarbonate and hydrogen ions. This bicarbonate ion is then carried in the plasma back to the lungs where it can participate in gas exchange. The correct answer emphasizes the biochemical nature of carbon dioxide transport, specifically noting the significant role of water in forming bicarbonate. While carbon dioxide can also be transported as dissolved gas and in association with hemoglobin or as carbamino compounds, these mechanisms account for a smaller proportion of total carbon dioxide transport compared to the bicarbonate system. Bicarbonate transport is crucial because it not only aids in carbon dioxide removal but also plays a role in maintaining acid-base balance in the body.

Most carbon dioxide in systemic capillaries is primarily transported in plasma as bicarbonate ions, which are formed when carbon dioxide combines with water. This reaction is catalyzed by the enzyme carbonic anhydrase, leading to the formation of carbonic acid, which quickly dissociates into bicarbonate and hydrogen ions. This bicarbonate ion is then carried in the plasma back to the lungs where it can participate in gas exchange.

The correct answer emphasizes the biochemical nature of carbon dioxide transport, specifically noting the significant role of water in forming bicarbonate. While carbon dioxide can also be transported as dissolved gas and in association with hemoglobin or as carbamino compounds, these mechanisms account for a smaller proportion of total carbon dioxide transport compared to the bicarbonate system. Bicarbonate transport is crucial because it not only aids in carbon dioxide removal but also plays a role in maintaining acid-base balance in the body.