Q.44 Given below are two statements : One is labelled as Assertion (A) and the other is labelled as
Reason (R).

Assertion (A) :In tertiary structure of protein hydrophbic side chains are held interior while the
hydrophilc groups are on the surface Of the protein molecule.

Reasons (R) : Other than hydrogen bonds disulifide bonds ( S —S ), ionic interaction
(Electrostatic), hydrophobic interaction and Vander Waals forces also contribute
to the tertiary structure Of protein.

In the light of the above statements, choose the most appropriate answer from the options given
below :
(1)Both (A) and (R) are correct and (R) is the correct explanation of (A)
(2)Both (A) and (R) are correct but (R) is NOT the correct explanation of (A)
(3)(A) is correct but (R) is not correct
(4)(A) is not correct but (R) is correct

Protein Tertiary Structure: Hydrophobic Core and Stabilizing Forces Assertion-Reason Solved

In protein tertiary structure, hydrophobic side chains cluster in the interior away from water, while hydrophilic groups remain on the surface for solvent interaction. Both assertion (A) and reason (R) are correct, but (R) lists general stabilizing forces without specifically explaining the hydrophobic-hydrophilic distribution, making option (2) correct.

Question Breakdown

Assertion (A) accurately describes the hydrophobic effect driving protein folding: nonpolar (hydrophobic) R-groups bury inside the core to minimize water contact, while polar/charged (hydrophilic) groups expose on the surface for solubility and interactions.
Reason (R) correctly identifies key non-covalent and covalent interactions stabilizing tertiary structure beyond hydrogen bonds: disulfide bridges (S-S), ionic bonds (electrostatic/salt bridges), hydrophobic interactions, and van der Waals forces.
(R) contributes to overall folding but does not directly explain why hydrophobic chains specifically localize interiorly—that’s primarily the hydrophobic effect.​

Option Analysis

• Option (1): Wrong—While both true, (R) describes general stabilizers; it doesn’t causally explain (A)’s specific hydrophobic interior positioning.​

• Option (2): Correct—Both statements factually accurate independently; hydrophobic distribution results mainly from solvent entropy, with (R) forces providing additional support.

• Option (3): Wrong—(R) correctly lists all major tertiary structure bonds/interactions (disulfide, ionic, hydrophobic, van der Waals).​

• Option (4): Wrong—(A) matches fundamental protein folding principle observed across globular proteins.​

Stabilizing Interactions