What happens to enzyme shape when the pH is outside its optimal range?

• A. Enzyme becomes more efficient
• B. Enzyme retains its shape and function
• C. Enzyme shape may change, affecting its function
• D. Enzyme site becomes more active

Answer: (C)

Enzymes are highly sensitive to changes in pH, as their shape and, consequently, their activity are influenced by the ionization state of their amino acid side chains. Each enzyme has an optimal pH range within which it functions most efficiently. When the pH moves outside of this optimal range, it can lead to the alteration of the ionization states of the amino acids that are crucial for maintaining the enzyme's three-dimensional structure.

This change can denature the enzyme, meaning its shape is altered in such a way that the active site—the part of the enzyme that binds to substrates—may no longer fit the substrate effectively. As a result, the enzyme's ability to catalyze reactions diminishes, affecting its overall function. Therefore, the assertion that enzyme shape may change, thus affecting its function, correctly reflects the relationship between pH and enzyme activity.