Name the ion and the molecule in blood that transports carbon dioxide generated by cellular respiration.

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The main idea is that carbon dioxide is carried in blood in two primary forms: primarily as bicarbonate ions in plasma, and secondarily bound to hemoglobin as carbaminohemoglobin. In tissues, CO2 enters red blood cells and, with the help of carbonic anhydrase, becomes carbonic acid and then bicarbonate and hydrogen ions. The bicarbonate is transported out into plasma in exchange for chloride, so most CO2 travels as HCO3− in the blood. A portion, however, binds directly to hemoglobin to form carbaminohemoglobin, providing another transport route for CO2. That’s why the best pairing is bicarbonate ion with hemoglobin. The other options either point to less important forms (like carbonate ion) or to carriers that don’t primarily handle CO2 (like albumin or water dissolved CO2).