Buffer system used in cell culture usually consists of sodium
bicarbonate-carbon dioxide system to maintain the pH balance. This
resembles the buffering system found in mammalian blood
stream.
This bicarbonate buffer system is defined as open becauses it
has the capacity of maintaining medium pH steady during cell
culture in the presence of CO2. The total concentration of buffer
within a compartment is not fixed in case of a open buffer system
whereas it is fixed in a closed buffer system.