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Biomolecules · Question 7

JEE Main 2026 (Online) 5th April Evening ShiftMCQEasy📈 Topic in 26% papers+4−1
1

Identify the incorrect statement about tertiary structure of proteins.

  1. They can be fibrous or globular in structure.
  2. The main forces that stabilize the structure are hydrogen bonding, disulphide links, van der Waals and electrostatic forces of attraction.
  3. The structure remains intact when exposed to pH changes.
  4. A linear polypeptide chain will convert to a secondary structure and then further folding of the secondary structure will convert to tertiary structure.

Answer

(3) The structure remains intact when exposed to pH changes.

Solution

(A) As per NCERT, the tertiary structure gives rise to two major molecular shapes – fibrous and globular ⇒ correct

(B) The tertiary structure is stabilised by hydrogen bonds, disulphide linkages, van der Waals and electrostatic forces of attraction ⇒ correct

(C) A change in pH disturbs the hydrogen bonds and ionic interactions; the protein uncoils and loses its 2° and 3° structure (denaturation), while the 1° structure stays intact ⇒ incorrect

(D) Polypeptide chain → coiling into secondary structure (α-helix / β-pleated sheet) → further folding into tertiary structure ⇒ correct

∴ The incorrect statement is (C).

Answer: (3)

JEE Main 2026 (Online) 5th April Evening Shift

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2

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 true
  2. Both Statement I and Statement II are false
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true
JEE Main 2026 (Online) 5th April Evening Shift
3

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 true
  2. Both Statement I and Statement II are false
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true
JEE Main 2026 (Online) 4th April Morning Shift
4

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

  1. A-II, B-I, C-IV, D-III
  2. A-IV, B-III, C-II, D-I
  3. A-III, B-IV, C-I, D-II
  4. A-II, B-IV, C-I, D-III
JEE Main 2026 (Online) 4th April Morning Shift
5

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]
JEE Main 2026 (Online) 4th April Evening Shift
6

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
JEE Main 2026 (Online) 2nd April Morning Shift
7

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
JEE Main 2026 (Online) 2nd April Evening Shift
8

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
JEE Main 2026 (Online) 28th January Morning Shift
9

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

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2026 (Online) 28th January Evening Shift
10

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
JEE Main 2026 (Online) 24th January Evening Shift
11

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
JEE Main 2026 (Online) 23rd January Morning Shift

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