BIOLOGY
CARBOHYDRATES
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Bial’s orcinol test
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Fehling’s Test
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Seliwanoff’s Test
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Barfoed Test
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Detailed explanation-1: -A positive test for pentoses is indicated by the formation of a bluish precipitate. A negative test is indicated by the formation of all other colours.
Detailed explanation-2: -The test is named after the scientist, Manfred Bial. Pentose form furfural in acidic medium. This furfural condenses with orcinol in the presence of ferric ions to form a blue-green-colored complex.
Detailed explanation-3: -Bial’s test is useful in distinguishing pentoses sugar from hexoses sugars. Pentosses ( such as ribose sugar) form furfural in acidic medium which condense with orcinol in presence of ferric ion to give blue green colored complex which is soluble in butyl alcohol.
Detailed explanation-4: -This is the Bial’s test on xylose. The solution changed to a blue/green color. This indicates that the sugar xylose is a furanose sugar. This is the Bial’s test on maltose.