What change would be expected in the cultures if an incubator ran out of carbon dioxide?

When an incubator runs out of carbon dioxide, the culture environment will experience an increase in pH, leading to a more alkaline condition. This happens because carbon dioxide, when dissolved in the medium, forms carbonic acid, which contributes to the acidity of the culture environment. If CO2 levels drop, there will be less carbonic acid formation, and consequently, the pH of the culture will rise as the buffering capacity of the medium is altered.

Maintaining proper CO2 levels is essential for various cell types, particularly those derived from mammalian sources, as they have adapted to physiologic conditions where CO2 levels are stabilized, thus ensuring balanced pH levels conducive to cell growth and metabolism. A higher pH can impact cellular functions and may eventually lead to reduced viability and function of the cultured cells if the imbalance persists. Hence, the anticipated change in pH due to a CO2 depletion scenario would be an increase, making the correct answer about the expected change in pH to be that it would be higher.