Q.13 Which one of the following media components is used to maintain pH in mammalian cell culture!
(A) CaCI2
(B) MgSO4
(C) Nacl
(D) NaHCO3
NaHCO3 serves as the key buffer to maintain pH in mammalian cell culture media, typically around 7.2-7.4, when paired with 5% CO2 in incubators. This multiple-choice question tests understanding of cell culture components, with option (D) NaHCO3 as the correct answer.
Option Analysis
Each option represents common media salts, but only one buffers pH effectively.
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(A) CaCl2: Provides calcium ions essential for cell adhesion, signaling, and membrane stability, but does not buffer pH.
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(B) MgSO4: Supplies magnesium as a cofactor for enzymes and supports metabolism, without influencing pH balance.
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(C) NaCl: Maintains osmotic pressure and ionic strength to mimic physiological conditions, not pH.
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(D) NaHCO3: Correct choice; forms a CO2/HCO3- buffering system that stabilizes pH against metabolic acids like lactic acid produced by cells.
pH Buffering Mechanism
NaHCO3 reacts with CO2 from the incubator: CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-, maintaining equilibrium at physiological pH. Media often contain 1.5-4.4 g/L NaHCO3, adjusted for 5-10% CO2 to prevent drift from cell metabolism.
