Description

Mechanisms in which CO2 is carried in the blood Blood arriving in alveoli has a higher carbon dioxide concentration that is during respiration by the cells in the body. Transportation of the CO2 in the blood is through three mechanisms: Dissolved CO2, Bound to hemoglobin and Bicarbonate ions (HCO3-).
Dissolved CO2
CO2 dissolves in plasma where it combines chemically with protein molecules to form a carbamino compound. In addition, CO2 combines with water forming a carbonic acid that ionizes into bicarbonate and hydrogen ions. About five percent of the total CO2 released by the lungs is dissolved too in the plasma.
Bound to hemoglobin
Hemoglobin, found in the red blood cells has the primary function of transporting oxygen from the lungs to the tissues and then transporting CO2 from the tissues back to the lungs. Deoxyhemoglobin is a form of hemoglobin that has a higher affinity form CO2. CO2 to hemoglobin and forms carbaminohemoglobin molecule. The process is reversible thus when it reaches the lungs, the CO2 dissociates freely from the hemoglobin and expelled from the body. This mechanism accounts for about ten percent of the CO2.
Bicarbonate ions (HCO3-)
CO2 diffuses into red blood cells where Carbonic anhydrase in the RBC quickly converts the CO2 into carbonic acid that is an unstable molecule. CA dissociates fast into bicarbonates ions and hydrogen ions which bind to hemoglobin. The bicarbonate ions formed is transported out of the RBC into the blood liquid component in exchange for a chloride ion. Upon the blood reaching the lungs, the bicarbonate ion is transported back into the RBC in exchange for chloride ion. The hydrogen ions dissociate from the hemoglobin and binds to the bicarbonate ion, producing carbonic acid, that through the enzymatic action of CA is converted back into CO2. The CO2 produced is expelled through exhalation by the lungs.
Works cited
Geers. C. and Gersolf . G. ” Carbon dioxide transport and carbonic anhydrase in blood and muscle.” Physiological reviews 80. 2 (2000): 681-715.