American Society for Clinical Pathology (ASCP) Technologist in Cytogenetics certification (ASCP CG) Practice Test

What would you expect to happen to the cultures if the incubator ran out of carbon dioxide overnight?

1. A decrease in temperature

2. A higher pH

3. An increase in carbon dioxide

4. No change in the cultures

The correct answer is: A higher pH

In the context of cell culture, particularly when dealing with mammalian cells, carbon dioxide (CO₂) plays a crucial role in maintaining physiological pH levels. Cultures are typically incubated in an atmosphere with a controlled CO₂ concentration to ensure a stable pH, primarily through the bicarbonate buffering system. When the incubator runs out of carbon dioxide, this leads to a reduction in carbonic acid levels in the culture medium, resulting in a decrease in the acidity and a corresponding increase in the pH. This shift towards a higher pH can negatively affect cell viability and functionality, as many cell types thrive within a specific pH range. Thus, the expectation of a higher pH if the incubator ran out of carbon dioxide overnight directly ties to the fundamental biochemical processes that maintain cell culture environments. Continual monitoring of CO₂ levels is essential for optimal culture conditions, underscoring the significance of CO₂ in maintaining pH balance in the medium.