Unit 2 - Testing for biological molecules Flashcards by Angelique Nguy | Brainscape

Q

Explain the iodine test.

A

Tests for the presence of starch
Add iodine dissolved in potassium iodide solution to test sample
If starch is present the colour will change from brown/orange to dark blue/black
If no starch is present, the colour stays brown/orange

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Q

What is used to test for starch?

A

Iodine

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Q

Why does iodine turn starch blue?

A

When dissolved in potassium iodide the iodine forms a tri-iodide ion, which slips into the middle of the amylose helix.

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