Question

the table shows the result of an experiment with the enzyme lactase. which conclusion is supported by the results of the experiment? enzymes act as biological catalysts. enzymes are used up in a biological reaction. enzymes are specific for a substrate. enzymes can act on more than two substrates.

Explanation:

• Analyze Test Tube 1 and 2: Test tube 1 (Milk + Lactase) has a positive result, while test tube 2 (Milk + Water) has a negative result. This shows that lactase (enzyme) is needed for a reaction with milk (substrate) to occur, but it does not directly show specificity yet.
• Analyze Test Tube 1 and 3: Test tube 1 (Milk + Lactase) has a positive result, and test tube 3 (Starch + Lactase) has a negative result. Lactase works on milk (a substrate with lactose) but not on starch (a different substrate). This indicates that lactase is specific to its substrate (lactose in milk), as it does not act on starch.
• Eliminate other options: The experiment does not show enzymes being used up (so option about enzymes being used up is wrong), nor does it show enzymes acting as catalysts in a way that distinguishes from other catalyst definitions (the "biological catalysts" option is not supported as the experiment focuses on specificity). Also, the experiment shows lactase acts on one substrate (milk - lactose) and not on starch, so the option about acting on more than two substrates is wrong. Thus, the conclusion that enzymes are specific for a substrate is supported.

Answer:

C. Enzymes are specific for a substrate.