Changes in temperature and pH affect what in enzymes?

Changes in temperature and pH affect what in enzymes?

• A. The amino acid sequence.
• B. The three-dimensional shape.
• C. The rate of transcription.
• D. The pH inside the nucleus.

Answer: (B)

Temperature and pH influence the three-dimensional arrangement of an enzyme. Enzymes rely on a precise folding pattern that creates the active site where substrates bind. The forces holding that fold together—hydrogen bonds, ionic interactions, and other noncovalent contacts—are sensitive to temperature and the protonation state of amino acids, which pH shifts can alter. When temperature is too high or pH moves outside an enzyme’s optimal range, these interactions can be disrupted, causing the protein to unfold or its shape to distort. If the active site changes shape, it may no longer fit the substrate well, so the enzyme’s catalytic activity drops or stops. The amino acid sequence itself doesn’t change under these conditions, and transcription or nuclear pH aren’t what’s directly being affected in this context.