A change of 1 pH unit in culture medium is caused by a change in CO2 concentration of how much?

The correct answer is based on the relationship between pH, hydrogen ion concentration, and carbon dioxide (CO2) levels in a buffered solution such as culture medium. The pH scale is logarithmic, meaning that each whole number change on the scale represents a tenfold change in hydrogen ion concentration.

When CO2 is introduced into a buffered aqueous solution, it forms carbonic acid, which dissociates into bicarbonate and hydrogen ions, thus affecting the pH. A change of 1 pH unit corresponds to a tenfold increase or decrease in hydrogen ion concentration. Therefore, a 1 unit change in pH indicates a 10-fold change in CO2 concentration when considering its effect on pH via this bicarbonate buffering system.

This understanding is rooted in the principles of acid-base chemistry and the behavior of buffers in biological systems, making the relation of a 1 pH unit change to a 10-fold change in CO2 concentration clear and substantiated.