Question

Biuret test is not given by ______.

Options

• carbohydrates

• polypeptides

• urea

• proteins

Answer 1

Biuret test is not given by carbohydrates.

Explanation:

When diluted CuSO₄ is added to an alkaline solution of a chemical containing peptide linkage, the biuret test yields a violet colour. Polypeptides, proteins and urea have\[\begin{array}{cc}\ce{- CO - NH - (Peptide)}\\
||\phantom{.................}\\\ce{O}\phantom{.................}
\end{array}\] linkage, while carbohydrates have glycostdic linkages. So, the test for carbohydrate should be distinct from the tests for the other three.