Q.163 Zoology ⭐ 360° Option Elimination Active

NEET 2023 Zoology Question 163 Solution

Topic: Biomolecules · Official NTA Booklet Code G5

Question

Given below are two statements: Statement I: Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat. Statement II: When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor. In the light of the above statements, choose the correct answer from the options given below:

(1)Statement I is false but Statement II is true.
(2)Both Statement I and Statement II are true.
(3)Both Statement I and Statement II are false.
(4)Statement I is true but Statement II is false.

✓

Verified Against NTA Final Answer Key

Option (2) : Both Statement I and Statement II are true.

📚 Biomolecules Easy

📋 Given Parameters & Problem Setup

Statement I Low temperature preserves enzyme in temporarily inactive state; high temp destroys activity via denaturation.

Statement II Inhibitor closely resembling substrate in molecular structure is known as competitive inhibitor.

⚡

The 30-Second Exam Hall Shortcut: ⚡ Enzyme Temperature Kinetics & Competitive Analogue Rules

⏱️ Save ~20 seconds

Low temperature causes kinetic dormancy (reversible inactivation), while high temperature permanently denatures tertiary protein structure. Competitive inhibitors are structural analogues of the substrate. Both statements are verbatim NCERT and TRUE!

1 Check Statement I: Low temp = temporary inactivity; High temp = permanent denaturation -> Verbatim NCERT, True.

2 Check Statement II: Inhibitor resembling substrate molecular structure = competitive inhibitor -> Verbatim NCERT, True.

3 Both Statement I and Statement II are true.

4 Match Option (2).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Biomolecules enzyme kinetics and inhibition definitions.

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Evaluation of Statement I (Thermal Effects on Enzymes)

Enzyme activity exhibits a bell-shaped curve across temperature. Sub-optimal low temperatures reduce thermal molecular kinetic collisions, locking the active site in a dormant state without breaking covalent bonds. Supra-optimal high temperatures disrupt weak hydrogen and ionic bonds stabilizing tertiary folding, causing irreversible denaturation:

\begin{aligned} \text{Low Temperature} & \longrightarrow \mathbf{\text{Temporarily Inactive (Reversible)}} \\[4pt] \text{High Temperature} & \longrightarrow \mathbf{\text{Protein Denaturation (Irreversible loss of activity)}} \end{aligned}

Step 2

Evaluation of Statement II (Competitive Inhibition)

When a chemical agent shares geometric and charge complementarity with the catalytic active site of an enzyme, competing with the physiological substrate:

\text{Substrate Analogue} \xrightarrow{\text{Competes for active site}} \mathbf{\text{Competitive Inhibitor}} \quad (\text{e.g., Malonate for Succinic Dehydrogenase})

Step 3

Verbatim NCERT Reference

NCERT states verbatim: - "Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat." (Statement I is TRUE) - "When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor." (Statement II is TRUE)

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 1

✗ Incorrect

Verdict & Scientific Reason:

Statement I is factually true: low temperature preserves enzymes in inactive states.

⚠️

Student Fallacy (Why candidates pick this trap): Thinking low temperature also denatures proteins.

2 2

✓ 100% Correct

Verdict & Scientific Reason:

Both statements are verbatim excerpts from NCERT Biomolecules.

💡

Why this is airtight: None; textbook verbatim recall.

3 3

✗ Incorrect

Verdict & Scientific Reason:

Both statements are sound biochemical truths.

⚠️

Student Fallacy (Why candidates pick this trap): Unsubstantiated skepticism regarding enzyme mechanisms.

4 4

✗ Incorrect

Verdict & Scientific Reason:

Statement II is factually true: defines competitive inhibition precisely.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing competitive inhibitors with allosteric non-competitive inhibitors.

⚠️

NTA Trap Alert: Inactivation vs. Denaturation Distinction Trap

Students frequently conflate cold inactivation with heat denaturation. Freezing does not denature enzymes (which is why biological samples are stored in liquid nitrogen); high heat breaks tertiary structure permanently.

🛡️ How to avoid the -1 mark: Cold = Temporary inactivity (preservation). Heat = Denaturation (destruction).

📖

Core NEET Syllabus Standard

NCERT Biology · Biomolecules Standard Benchmark

Core Scientific Principle Tested:

"Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat."

Syllabus Focus: Enzymes (Factors Affecting Enzyme Activity)

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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Classification & Functions of Biomolecules (Proteins, Polysaccharides & Secondary Metabolites)

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NEET 2023 Zoology Question 163 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Enzyme Temperature Kinetics & Competitive Analogue Rules

Step-by-Step Rigorous Workflow & Mathematical Proof

Evaluation of Statement I (Thermal Effects on Enzymes)

Evaluation of Statement II (Competitive Inhibition)

Verbatim NCERT Reference

360° Option Elimination Engine Key Feature

NTA Trap Alert: Inactivation vs. Denaturation Distinction Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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