Lugol's iodine indicates the presence of which substance?

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Prepare for the PLTW Biomedical Science Test. Study with flashcards and multiple choice questions, each question comes with hints and explanations. Get ready for your exam!

Multiple Choice

Lugol's iodine indicates the presence of which substance?

Explanation:
Lugol's iodine tests for starch. The iodine molecules slip into the helical structure of amylose in starch and form a blue-black complex, so a positive result appears as a dark purple/blue color. If starch isn’t present, the solution stays the typical yellow-brown color of iodine. This reagent doesn’t indicate sugar, protein, or fat—simple sugars don’t create the starch-iodine complex, and those other substances require different tests to reveal their presence.

Lugol's iodine tests for starch. The iodine molecules slip into the helical structure of amylose in starch and form a blue-black complex, so a positive result appears as a dark purple/blue color. If starch isn’t present, the solution stays the typical yellow-brown color of iodine. This reagent doesn’t indicate sugar, protein, or fat—simple sugars don’t create the starch-iodine complex, and those other substances require different tests to reveal their presence.

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