Which of the following statements about a mixture of a protein-digesting enzyme and starch solution would be correct? The protein-digesting enzyme

Step 1: Analyze the question We have a protein-digesting enzyme (a protease, such as pepsin or trypsin) mixed with a starch solution. We need to decide what the enzyme does to the starch.

Step 2: Explain the concept Enzymes are substrate-specific. This is the "lock and key" idea: the active site of an enzyme fits only one kind of substrate.

• Protease acts on proteins and breaks them into amino acids.
• Amylase acts on starch and breaks it into maltose, and later glucose.
• Lipase acts on fats and breaks them into fatty acids and glycerol.

Step 3: Work through the options

• A. Has no effect on the starch solution. Correct. Starch is not the substrate of a protease, so the enzyme cannot bind to it and nothing happens.
• B. Leads to the production of amino acids. Wrong. Amino acids come from protein digestion. The mixture contains only starch, which has no protein to break down.
• C. Leads to the production of glucose. Wrong. Glucose comes from starch digestion by amylase, not by a protease.
• D. Digest the starch. Wrong. A protease cannot digest starch because of enzyme specificity.

Step 4: Answer The correct option is A. The protein-digesting enzyme has no effect on the starch solution.

Exam tip: When a question pairs an enzyme with the wrong substrate, think "specificity". Use the name of the enzyme as a clue: Protease → Protein, Amylase → Starch (amylum), Lipase → Lipids. If the enzyme and substrate do not match, the answer is "no effect".