When carbon dioxide (CO2) dissolves in plasma, it forms bicarbonate ions (HCO3-) and hydrogen ions (H+). Here's the breakdown:

1. CO2 reacts with water: CO2 dissolved in plasma reacts with water (H2O) to form carbonic acid (H2CO3):

CO2 + H2O ⇌ H2CO3

2. Carbonic acid dissociates: Carbonic acid then dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+):

H2CO3 ⇌ HCO3- + H+

This reaction is reversible, meaning that the formation of bicarbonate and hydrogen ions is in equilibrium with the reformation of carbonic acid.

The overall reaction is:

CO2 + H2O ⇌ HCO3- + H+

This process is crucial for maintaining the blood's pH balance. The bicarbonate ions act as a buffer, helping to resist changes in pH.