Describe the test for reducing sugars....

Describe the test for reducing sugars.

Text Solution

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Aldoses and ketoses are reducing sugars. This means that, when heated with an alkaline solution of copper (II) sulphate (a blue solution called benedict.s solution), the aldehyde or ketone group reduces Cu2+ ions to Cut ions forming brick red precipitate of copper (I) oxide. In th eprocess, the aldehyde or ketone group is oxidised to a carboxyl group (-COOH). This reaction is used as test for reducing sugar and is known as Benedict.s test. The results of benedict.s test depends on concentration of the sugar. If there is no reducing sugar it remains blue.
(i) Sucrose is not a reducing sugar.
(ii) The greater the concentration of reducing sugar, the more is the precipitate formed and greater is the colour change.

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____is not a reducing sugar.

Glucose

Fructose

Sucrose

Ketose

Assertion(A): Maltose, a disaccharide acts as a reducing sugar. Reason (R): Maltose consists of two molecules of alpha - D glucose with linked by alpha 1,4 - glycosidic bond and one glucose has the carbonyl group.

Both A and R are correct and R is the correct explanation of A

Both A and R are correct but R is not the correct explanation of A .

A is correct but R is wrong.

A is wrong but R is correct

Assertion(A): A disaccharide lactose act as reducing sugar. Reason (R): In lactose, beta - D galactose and beta - D glucose are linked beta - 1, 4 - glycosidic bond in which aldehyde group is not involved.

A is correct but R is wrong.

Both A and R are correct but R is not the correct explanation of A.

Both A and R are correct and R is the correct explanation of A.

Ais wrong but R is correct.