Carbon dioxide is an important byproduct of metabolism that needs to be removed from the body using transport to the lungs and subsequent expiration out into the surrounding environment. There are three major transport mechanisms for CO2:

1. Dissolved gas: About 7% of CO2 is carried in a dissolved state in the plasma.

2. Bicarbonate: Carbon dioxide reacts with water to form carbonic acid, which almost immediately dissociates into a bicarbonate anion (HCO3-) and a proton. Bicarbonate is the primary means by which carbon dioxide is transported throughout the bloodstream.

3. Carbaminohemoglobin: Carbon dioxide can enter red blood cells and bind to hemoglobin, forming carbaminohemoglobin. This form transports about 10% of the carbon dioxide.

The majority of carbon dioxide is transported as part of the bicarbonate system. Carbon dioxide diffuses into red blood cells, where carbonic anhydrase converts it into carbonic acid, which dissociates into bicarbonate and a proton. As carbon dioxide continues to be produced by tissues, this reaction is continually driven forward in the periphery, according to Le Chateliers principle.