Biomolecules JEE Main PYQs (2020–2026)

Solved Biomolecules PYQs

3 recent questions with answers. The full set of 149 is free to practise.

1. JEE Main 2026EasyPeptides and Proteins: Structure, Classification and Denaturation
   Q1

   Identify the incorrect statement about tertiary structure of proteins.

   • AThey can be fibrous or globular in structure.
   • BThe main forces that stabilize the structure are hydrogen bonding, disulphide links, van der Waals and electrostatic forces of attraction.
   • CThe structure remains intact when exposed to pH changes.
   • DA linear polypeptide chain will convert to a secondary structure and then further folding of the secondary structure will convert to tertiary structure.

   Show answer & solution

   Correct answer: (C)

   When the pH changes, the tertiary structure of a protein gets disturbed or broken. However, the amino acids in the protein remain connected to each other through peptide bonds.
2. JEE Main 2026MediumVitamins and Hormones
   Q2

   Identify the correct pair having amino acid (A) and the hormone (B) that is iodinated derivative of the amino acid (A).
   
   (T and Y represent one letter code for amino acids)

   • AAmino acid (A) - T Hormone (B) - Insulin
   • BAmino acid (A) - T Hormone (B) - Thyroxine
   • CAmino acid (A) - Y Hormone (B) - Thyroxine
   • DAmino acid (A) - Y Hormone (B) - Insulin

   Show answer & solution

   Correct answer: (C)

   The correct pair is:
   
   $$\text{Amino acid (A) = Y, Hormone (B) = Thyroxine}$$
   
   So, the correct option is:
   
   $$\boxed{\text{Option C}}$$
   
   Reason:
   
   The one-letter code $Y$ stands for tyrosine.
   
   Thyroxine is an iodinated derivative of tyrosine.
   
   Insulin is a protein hormone, not an iodinated derivative of an amino acid.
   
   Hence,
   
   $$\boxed{Y\to \text{Thyroxine}}$$
3. JEE Main 2026EasyNucleic Acids: DNA and RNA
   Q3

   Both human DNA and RNA are chiral molecules. The chirality in DNA and RNA arises due to the presence of

   • AL-sugar component
   • BD-sugar component
   • CChiral phosphate unit
   • DBase unit

   Show answer & solution

   Correct answer: (B)

   DNA and RNA show chirality because they contain a chiral sugar in their structure.
   
   In DNA, the sugar present is chiral 2-deoxy-Ribose.
   
   In RNA, the sugar present is chiral Ribose.

Topic-wise question count

Where JEE Main has asked from Biomolecules, most frequent first.

• Peptides and Proteins: Structure, Classification and Denaturation32
• Carbohydrates: Monosaccharides (Structure and Reactions)31
• Carbohydrates: Disaccharides and Polysaccharides28
• Amino Acids: Classification, Properties and Tests21
• Vitamins and Hormones16
• Nucleic Acids: DNA and RNA16
• Enzymes and Coenzymes5

Year-wise Biomolecules questions in JEE Main

Number of questions from this chapter in each year's paper(s).