Question

A reagent added to a sample shows change of colour from green to yellow. It is due to the presence of reducing sugar. The test is -
a. Elisa Test for detecting AIDS
b. Benedict’s Test for detecting glucosuria
c. Fehling test for detecting hyperglycemia
d. Ninhydrin test for detecting glycosidic linkage

Answer 1

Hint: Due to the free aldehyde group or a free ketone group reducing sugar is a reducing agent. Alongside some disaccharides, oligosaccharides, and polysaccharides, all monosaccharides are considered as reducing sugars. Reducing sugars is utilized in browning by reacting with proteins in baking.

Complete answer:
> Benedict's test is a chemical examination that can be used to confirm the presence of reducing sugars in a given analyte. The test is based on Benedict's reagent, which is a complicated mixture of sodium citrate, sodium carbonate, and the pentahydrate of copper (II) sulfate.

> Benedict's test can be utilized to investigate reducing sugar that is glucose in urine. Glucose turns yellow in color when Benedict's test is applied and it shows that glucose is present in urine. Glucose in urine is known as glucosuria.

> Result elucidation of Benedict's test is that if the color after boiling is changed into green, after that there would be 0.1 to 0.5 percent sugar in the solution. If it transforms color to yellow, then 0.5 to 1 percent sugar is present. If it amends to orange, then it implies that 1 to 1.5 percent sugar is there.

> ELISA is a usually used laboratory test to identify antibodies in the blood. Fehling's solution is a chemical reagent used to discriminate between water-soluble carbohydrate and ketone functional groups. Ninhydrin is used to perceive ammonia or primary and secondary amines.

Hence, the correct answer is option (B).

Note: The color of benedict's solution is deep-blue. It is a dilute alkaline mixture of copper sulfate and sodium citrate. Sodium citrate is a complexing agent that keeps cupric ion in solution, which would or else precipitate as cupric carbonate. Sodium carbonate serves to keep the solution alkaline. It reacts chemically likewise to Fehling's solution; the cupric ion is transformed to cuprous ion by the aldehyde group (which is oxidized) and precipitates as cuprous oxide, cupric oxide.