Above and below an enzyme's optimum pH, activity drops because
- A
Water molecules surrounding the enzyme freeze at extreme pH, blocking diffusion of substrate to the active site
- B
Hydrogen ions in the cytosol bind directly to substrate, preventing the substrate from reaching the active site
- Ccheck_circle
Charged residues in the active site change protonation state, altering substrate binding and catalysis
- D
Ribosomes near the enzyme misfold the protein chain at non-optimal pH, producing a permanently inactive enzyme
Explanation
pH determines the protonation of acidic/basic side chains; outside the optimum, the active site geometry and chemistry are wrong.