Interpreting biochemical test results for sugars, starch, and enzymes

Steps:

• Identify positive starch test (e.g., blue-black with iodine) indicating starch presence.
• Check for non-reducing sugar: negative Benedict's but positive after hydrolysis, confirming sucrose.
• Observe catalase activity: bubbles from H2O2 decomposition, indicating catalase enzyme.
• Rule out reducing sugars like glucose, as initial Benedict's test is negative.

Why D is correct:

• Sucrose gives negative Benedict's (non-reducing) but positive after acid hydrolysis; starch turns blue with iodine; catalase produces oxygen gas with H2O2, per enzyme-substrate reaction.

Why the others are wrong:

• A: Glucose is reducing sugar (positive Benedict's), contradicting negative initial test; amylase/lipase not indicated.
• B: Glucose present would show positive Benedict's, but test is negative.
• C: Amylase is enzyme (no specific test shown); triglyceride would emulsify with ethanol, but no lipid test positive.

Final answer: D