Decreasing the pH of an enzyme solution from 6.8 to 5.8 causes the rate of the reaction to fall by 80%. When the pH of the solution is returned to 6.8, the rate of reaction returns to its original value. Which of the statements about this enzyme-controlled reaction explains these observations?
Decreasing the pH from 6.86.86.8 to 5.85.85.8 breaks hydrogen and ionic bonds, but returning the pH to 6.86.86.8 allows them to re-form.
Decreasing the pH from 6.86.86.8 to 5.85.85.8 changes the shape of the active site so that the substrate binds more tightly.
Decreasing the pH from 6.86.86.8 to 5.85.85.8 denatures the enzyme.
Increasing the pH above 6.86.86.8 will increase the rate of reaction.
9 exam-style questions on OCR A A Level Biology Enzymes. Each one has a worked solution and a mark scheme showing where the marks go.