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Why is CO2 used in cell culture incubator?

Public Comments

1. To culture cells under stable conditions the media they grow in needs to be buffered so it stays at neutral pH (around pH 7). It is possible to add a buffering compound to the media, like sodium phosphates or Tris or Hepes, but often these compounds affect the cells' growth. A carbonate buffer system, of HCO3- and H2CO3 has been found to affect the growth of cells the least. H2CO3 in water is in equilibrium with H2O+CO2. To keep the CO2 in the buffer solution at the right level you have to supply CO2 in the atmosphere above the buffer, otherwise all the CO2 would dissipate and the H2CO3 would disappear and there would be no more buffering effect (and the medium would become alkaline). So when you use a CO2 cell culture incubator, make sure the media contains HCO3- (usually from NaHCO3).