Which of the following statements is TRUE regarding CO2 in the mammalian bloodstream? In the mammalian bloodstream, CO2 is much less soluble than O2. CO2 is mainly transported through the mammalian bloodstream in the form of bicarbonate ions or carbonic acid. Unlike oxygen, CO2 is transported through the mammalian bloodstream by myoglobin. All CO2 is transported through the mammalian bloodstream as a dissolved gas, and is carried directly in the plasma. Like oxygen, CO2 is transported through the mammalian bloodstream via hemoglobin; however, CO2 binds to hemoglobin at β subunits rather than heme groups.

Carbon dioxide is eliminated from the human body via three different methods. The first method of elimination is direct dissolution in the blood: in this case, carbon dioxide dissolves in the blood and is excreted via the lungs. About 7% of all carbon dioxide are eliminated through this method.

The second method involves the binding of carbon dioxide to hemoglobin. This binding is reversible and the carbon dioxide can easily dissociate from the hemoglobin in order to be excreted in the lungs. About 10% of carbon dioxide are eliminated from the body by this method.

The third method of carbon dioxide elimination involves the formation of bicarbonates ions and carbonic acid. Majority of the carbon dioxide in the body ( about 85%) are eliminated from the body through this method.