Carbon dioxide is converted into bicarbonate in the cytoplasm of the red blood cells through the enzyme.
The correct answer and explanation is:
The enzyme responsible for converting carbon dioxide (CO₂) into bicarbonate (HCO₃⁻) in the cytoplasm of red blood cells is carbonic anhydrase.
Carbonic anhydrase is a crucial enzyme that catalyzes the reversible conversion of carbon dioxide and water into carbonic acid, which quickly dissociates into bicarbonate and a hydrogen ion (H⁺). This reaction is essential in the transport of CO₂ from tissues to the lungs.
Here’s how the process works: In tissues, cells produce CO₂ as a waste product of cellular respiration. This CO₂ diffuses into the bloodstream, where it enters red blood cells. Inside the red blood cells, carbonic anhydrase speeds up the conversion of CO₂ and water into carbonic acid. The carbonic acid then dissociates into bicarbonate ions (HCO₃⁻) and hydrogen ions (H⁺). The bicarbonate ions are transported out of the red blood cells and into the plasma, while chloride ions (Cl⁻) move into the red blood cells in a process known as the Chloride shift. This maintains electrical neutrality across the red blood cell membrane.
As blood travels to the lungs, the process is reversed. The bicarbonate ions re-enter the red blood cells, combining with hydrogen ions to form carbonic acid. Carbonic anhydrase then catalyzes the breakdown of carbonic acid into CO₂ and water. The CO₂ is then exhaled from the lungs.
This process is critical in maintaining the pH of the blood and in facilitating the efficient transport and elimination of CO₂, ensuring that the body can effectively manage the acid-base balance in response to metabolic activities.