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Biomolecules

JEE Main 2026 (Online) 4th April Evening ShiftMCQHard📈 Topic in 26% papers+4−1
Ques. 1JEE Main 2026, 4 April (Evening Shift)

A D-aldotetrose on oxidation with concentrated HNO3 resulted in optically inactive dicarboxylic acid. The structure of the D-aldotetrose is:

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]

Answer

(3) [figure]

Solution

An aldotetrose has two chiral carbons (C-2 and C-3). Conc. HNO3 oxidises both –CHO and –CH2OH to –COOH ⇒ 2,3-dihydroxybutanedioic acid (tartaric acid).

It is optically inactive only in the meso form, which has a plane of symmetry ⇒ both –OH on the same side of the Fischer projection.

D-sugar ⇒ –OH on C-3 (the carbon next to –CH2OH) on the right ⇒ –OH on C-2 also on the right ⇒ D-erythrose.

[figure]

∴ Option (3). (Option (4) is D-threose, which gives optically active tartaric acid; (1) and (2) are L-sugars.)

Answer: (3)

Keep practising — Biomolecules

Ques. 2JEE Main 2026, 2 April (Morning Shift)

Match List - I with List - II.

  1. A-II, B-I, C-III, D-IV
  2. A-IV, B-III, C-II, D-I
  3. A-III, B-IV, C-I, D-II
  4. A-I, B-III, C-II, D-IV
Ques. 3JEE Main 2026, 2 April (Evening Shift)

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)

  1. Amino acid (A) - T Hormone (B) - Insulin
  2. Amino acid (A) - T Hormone (B) - Thyroxine
  3. Amino acid (A) - Y Hormone (B) - Thyroxine
  4. Amino acid (A) - Y Hormone (B) - Insulin
Ques. 4JEE Main 2026, 28 January (Morning Shift)

In the given pentapeptide, find out an essential amino acid (Y) and the sequence present in the pentapeptide : [figure] Choose the correct answer from the options given below :

  1. arrayll(Y) & (Sequence) \ Serine & Thr-Ser-Asp-Ala-Gly array
  2. arrayll(Y) & (Sequence) \ Serine & Ser-Asp-Thr-Ala-Gly array
  3. arrayll(Y) & (Sequence) \ Threonine & Ser-Thr-Asp-Gly-Ala array
  4. arrayll(Y) & (Sequence) \ Threonine & Thr-Ser-Asp-Gly-Ala array
Ques. 5JEE Main 2026, 28 January (Evening Shift)

Structures of four disaccharides are given below. Among the given disaccharides, the non-reducing sugar is :

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 6JEE Main 2026, 24 January (Evening Shift)

The number of possible tripeptides formed involving alanine (ala), glycine (gly) and valine (val), where no amino acid has been used more than once is:

  1. 8
  2. 3
  3. 4
  4. 6
Ques. 7JEE Main 2026, 23 January (Morning Shift)

From the given following (A to D) cyclic structures, those which will not react with Tollens' reagent are: [figure]

  1. A and D
  2. A and B
  3. B and D
  4. B and C
Ques. 8JEE Main 2026, 23 January (Evening Shift)

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

  1. L-sugar component
  2. D-sugar component
  3. Chiral phosphate unit
  4. Base unit
Ques. 9JEE Main 2026, 22 January (Morning Shift)

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Both Statement I and Statement II are false
  2. Both Statement I and Statement II are true
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true
Ques. 10JEE Main 2026, 22 January (Evening Shift)

Match List-I with List-II. Choose the correct answer from the options given below :

  1. A-IV, B-III, C-II, D-I
  2. A-I, B-III, C-IV, D-II
  3. A-III, B-I, C-IV, D-II
  4. A-IV, B-I, C-II, D-III
Ques. 11JEE Main 2026, 21 January (Morning Shift)

Identify the correct statements. Choose the correct answer from the options given below :

  1. C and D Only
  2. A and D Only
  3. C and E Only
  4. B and E Only

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