Correct option is A
CO₂ Concentration in Culture Media:
- RPMI (Roswell Park Memorial Institute medium) and DMEM (Dulbecco's Modified Eagle Medium) are two commonly used cell culture media.
- CO₂ concentration is crucial because it helps maintain the pH balance in the culture medium.
- RPMI is optimized with 5% CO₂.
- DMEM, on the other hand, requires a slightly higher concentration of CO₂ (7.5-10%).
- The CO₂ dissolves in the medium and forms carbonic acid, which helps in maintaining the pH of the culture medium by neutralizing the effects of acidic metabolic waste products from cells.
HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid):
- HEPES is a buffering agent that is used in cell culture media, particularly when cells are kept outside the incubator in room air.
- HEPES helps maintain the pH in the culture medium when the usual buffering system (CO₂ and NaHCO₃) is not available, such as when the cells are placed in an incubator-free environment.
- HEPES ensures that the pH remains stable, preventing it from dropping (which could happen if only NaHCO₃ were used in ambient air).
NaHCO₃ (Sodium Bicarbonate):
- NaHCO₃ is another buffering agent commonly used in cell culture media.
- NaHCO₃ works effectively in combination with CO₂ in the incubator, where CO₂ is dissolved in the culture medium and reacts with NaHCO₃ to stabilize the pH.
- However, in environments outside the incubator (where CO₂ is absent), NaHCO₃ is not sufficient by itself to maintain a stable pH, which is why HEPES is often used in these conditions.
Phenol Red:
- Phenol red is a pH indicator that is commonly added to culture media to monitor the pH visually.
- In a neutral environment, phenol red appears red/pink.
- If the pH becomes acidic (as a result of metabolic activity of cells), the phenol red turns yellow.
- Conversely, if the pH becomes alkaline, phenol red can turn orange/red
Option 1: A and B is the correct answer
