Final answer:
Carbon dioxide in the blood is principally transported as bicarbonate dissolved in plasma, using a process involving the enzyme carbonic anhydrase and the chloride shift mechanism.
Step-by-step explanation:
Carbon dioxide is transported in the blood primarily as bicarbonate dissolved in plasma. This biological process is critical for maintaining acid-base balance in the body and enabling carbon dioxide, a waste product of cellular metabolism, to be expelled from the lungs during respiration.
Only a small proportion of carbon dioxide, about 5 to 7 percent, is transported via dissolution directly into the blood plasma. Another 10 percent is bound to hemoglobin in red blood cells, forming carbaminohemoglobin. However, the majority of carbon dioxide is carried in the blood after being converted to bicarbonate ions (HCO3-). This conversion involves carbonic anhydrase, an enzyme in erythrocytes that catalyzes the transformation of carbon dioxide and water into carbonic acid, which then dissociates into bicarbonate and hydrogen ions.
The bicarbonate ions are transferred into plasma by the chloride shift, ensuring that a greater amount of carbon dioxide can be transported in the blood to the lungs for elimination. The entire process is reversed in the lungs, allowing carbon dioxide to be exhaled, thus completing the cycle of gas exchange essential for breathing.