What is a correct statement about biological molecules?
A) Biuret reagent is used to test for reducing sugars.
B) Glycogen is made of smaller glycerol molecules.
C) Oils contain the chemical elements carbon, hydrogen, oxygen and nitrogen.
D) Protein is made of smaller amino acid molecules.
▶️ Answer/Explanation
Ans: D
Option D is correct because proteins are polymers composed of smaller subunits called amino acids. Option A is incorrect as Biuret reagent tests for proteins, not reducing sugars (Benedict’s reagent is used for that). Option B is wrong because glycogen is made of glucose monomers, not glycerol. Option C is incorrect because oils (lipids) contain only carbon, hydrogen, and oxygen, not nitrogen.
Thus, the only accurate statement is D (Protein is made of smaller amino acid molecules).
A student tests a solution for protein. Which row shows the correct food test and a positive result?
▶️ Answer/Explanation
Ans: D
To test for proteins, the Biuret test is used. In this test, a solution turns violet or purple when proteins are present. Row D correctly identifies the Biuret test and the expected positive result.
Benedict’s test (A) is for reducing sugars, iodine (B) tests for starch, and the emulsion test (C) is for lipids. Since the question asks for protein detection, the answer is D.