The steps below are involved in the testing of a leaf for starch. Study them carefully and answer the question: I. Decolorize them II. Dip decolorized leaf ...

Assessment: WAEC SSCE - Biology - 2016 (Objective) Subject: Biology

Question 1 Report

The steps below are involved in the testing of a leaf for starch. Study them carefully and answer the question:

I. Decolorize them

II. Dip decolorized leaf in warm water

III. Place leaf in boiling water

IV. Add iodine solution

The CORRECT order for the test is?

Answer Details
The correct order for testing a leaf for starch is: III, I, II, and IV. First, the leaf is placed in boiling water to kill the cells and denature the enzymes that could break down starch. Next, the decolorizing step removes chlorophyll from the leaf, making it easier to observe the presence of starch. Then, the leaf is rinsed with warm water to soften it and make it easier to spread. Finally, iodine solution is added to the leaf, and if starch is present, the iodine will react with the starch, turning it blue-black.

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