How does cellular respiration affect pH?
Cellular respiration increases the acidity of the pH of the environment.
One of the products of cellular respiration is Carbon Dioxide
Carbon Dioxide can dissolve into water forming Carbonic Acid.
As an acid the Carbonic Acid has a pH of about 5. Water has a pH of about 7. So adding Carbonic Acid to the environment will lower the pH causes the environment to become more acidic in pH.
Note carbonated drinks use dissolved Carbon Dioxide for the fizz.
The Carbon Dioxide in the "soda" will form Carbonic Acid. This means that all sodas are weak acids. Place a tooth into Coke and in a few days the acid in the soda will dissolve the tooth completely.