Which statement is true about testing lipase activity in a strongly acidic buffer?

• A. The buffer prevents observation of activity by keeping pH at 2.0.
• B. Lipase activity is unaffected by buffer pH.
• C. Lipase becomes more active under such buffer.
• D. The substrate becomes unavailable.

Answer: (A)

The test here hinges on how pH controls enzyme activity. Lipase has an optimum pH range closer to neutral to mildly alkaline, and a strongly acidic environment disrupts its structure and the chemistry of catalytic residues. In a buffer that holds the pH at 2.0, the enzyme becomes inactive, so you wouldn’t observe any lipase activity. That’s why this statement is true: the buffer prevents observation of activity by keeping the pH at 2.0.

Enzyme activity is not pH invariant, so saying it’s unaffected isn’t accurate. Saying the enzyme becomes more active in such acidic conditions contradicts how lipase typically behaves. And while the substrate might still be present, the lack of enzyme activity at pH 2 is the key limiting factor, not substrate availability.