What is the purpose of including a tube with amylase, deionized water, and buffer in a starch digestion experiment?

• A. To confirm enzyme activity in the absence of substrate
• B. To measure starch concentration
• C. To increase reaction rate
• D. To test enzyme stability at high temperature

Answer: (A)

The main idea here is using a negative control to verify that any breakdown you observe depends on starch being present. A tube that contains amylase, buffer, and deionized water but no starch cannot produce maltose or glucose because there is no substrate for the enzyme to act on. If this tube shows no change, it confirms that the assay’s readout in the experimental tubes comes from amylase acting on starch, not from the enzyme, buffer, or water causing a false signal. In other words, it rules out background reactions or contamination as sources of change. If any change were detected in this control, it would suggest there’s some non-substrate-related factor producing a signal, so you’d question whether observed digestion in the other tubes is truly due to starch breakdown.