About 70% of carbon dioxide is transported in deoxygenated blood:

The transportation of carbon dioxide in deoxygenated blood occurs in three main ways:

1. Dissolved in plasma: About 7% of carbon dioxide is carried in the plasma as a dissolved gas.

2. Bound to hemoglobin: Approximately 23% of carbon dioxide binds with hemoglobin and is transported in the red blood cells.

3. Bicarbonate ions: The majority of carbon dioxide, about 70%, is transported in the blood as bicarbonate ions. This occurs through a series of reactions. First, carbon dioxide combines with water inside the red blood cells, forming carbonic acid. This reaction is catalyzed by an enzyme called carbonic anhydrase. The carbonic acid then quickly dissociates into hydrogen ions and bicarbonate ions. The bicarbonate ions pass out of the red blood cells into the plasma, and this is how most of the carbon dioxide is transported in the blood.