A reagent added to a sample to a shows change of colour from green to yellow. It is due to presence of reducing sugar. The test is

Options

A. Elisa test for detecting AIDS
B. Benedict's test for detecting glucosuria
C. Fihling's test for detecting hyperglycemia
D. Ninhydrin test for detecting glucosidic linkage.

Answer

**Step-by-Step Solution:**

1. **Understanding the Test**: The question states that a reagent added to a sample shows a color change from green to yellow, indicating the presence of a reducing sugar.

2. **Identifying the Reagent**: The reagent used for detecting reducing sugars is typically Benedict's reagent, which is a blue solution of copper(II) sulfate.

3. **Chemical Reaction**: When a reducing sugar is present and the solution is heated, the copper(II) ions in the Benedict's reagent are reduced to copper(I) oxide, which precipitates out of the solution. This reaction can produce various colors depending on the concentration of the reducing sugar.

4. **Color Change Interpretation**: The color change from green to yellow indicates that there is a low concentration of reducing sugar present. A more concentrated solution would yield colors ranging from yellow to orange to brick red.

5. **Conclusion**: Based on the color change observed (green to yellow), it can be concluded that the test being referred to is the Benedict's test.

6. **Clinical Relevance**: The presence of reducing sugars, particularly glucose, in urine can indicate conditions such as diabetes mellitus, where glucose levels exceed the renal threshold.

**Final Answer**: The test is the **Benedict's test**.

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