Why can't lipase activity be fully tested in test tube 5?

• A. The pH buffer remained at 2.0 despite fatty acid release.
• B. The enzyme is not present in the tube.
• C. The oil substrate was absent.
• D. The temperature was too low for activity.

Answer: (A)

The test is measuring lipase activity by the change it causes in pH as fatty acids are released from triglycerides. In this tube, the pH buffer keeps the solution at a fixed pH of 2.0, even though fatty acids are being produced. Because the pH doesn’t shift, the typical readout for enzyme activity (pH change) can’t reflect how much lipase is working. So, the enzyme’s activity can’t be fully assessed—the strong buffering hides the signal you rely on to quantify lipase activity. If you wanted to measure activity, you’d use a weaker buffer or another readout less dependent on pH, such as tracking fatty acid concentration directly or measuring glycerol release.