A change in pH away from the optimum reduces enzyme activity because it
- A. reduces the number of substrate molecules present
- B. alters the charges on the R groups, changing the shape of the active site
- C. lowers the temperature of the mixture
- D. converts the enzyme into a substrate
Explanation
Excess hydrogen or hydroxide ions interfere with the ionic and hydrogen bonds between the side chains that hold the tertiary structure, so the active site distorts and the substrate no longer fits. A small shift is reversible, but an extreme one denatures the enzyme permanently. This is why pepsin works at pH 2 and trypsin at pH 8 and neither is active in the other's conditions.
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