# How does pH affect cellular respiration?

Acids are substances that contain ${H}^{+}$ ions, while alkalis contain $O {H}^{-}$ ions - so pH is essentially a measure of how many ${H}^{+}$ ions are in a substance. Therefore, if the enzymes environment has a lower than optimum pH, there will be more ${H}^{+}$ ions, which could result in the bonds between the enzyme's amino acids being changed - therefore changing the shape and denaturing it.