Q.149 Zoology ⭐ 360° Option Elimination Active

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NEET 2025 Zoology Question 149 Solution

Topic: Biomolecules · Official NTA Booklet Code 45

Question

The protein portion of an enzyme is called:

(1)Cofactor
(2)Coenzyme
(3)Apoenzyme
(4)Prosthetic group

✓

Verified Against NTA Final Answer Key

Option (3) : Apoenzyme

📚 Biomolecules Easy

📋 Given Parameters & Problem Setup

Target Structure Protein portion of a conjugated catalytic enzyme

⚡

The 30-Second Exam Hall Shortcut: ⚡ Enzyme Terminology Equation Fingerprint

⏱️ Save ~10 seconds

Holoenzyme = Apoenzyme (PROTEIN part) + Co-factor (NON-PROTEIN part)! Protein portion alone is the APOENZYME!

1 Recall the holoenzyme breakdown equation from NCERT Section 9.12.6:

2 - Holoenzyme (active catalytic complex) = Apoenzyme + Co-factor.

3 - Protein portion of the enzyme = Apoenzyme.

4 - Non-protein portion = Co-factor (prosthetic group, coenzyme, or metal ion).

5 Direct answer: Apoenzyme!

6 Select Option (3) Apoenzyme!

🛡️

Why You Can 100% Trust This Shortcut: Enzyme Kinetics & Competitive Inhibition (NCERT Biology · Biomolecules: Malonate competitive inhibition of succinate dehydrogenase).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Composition of Conjugated Enzymes (Holoenzymes)

Many enzymes are conjugated proteins composed of two distinct biochemical entities:

• Apoenzyme: The macromolecular protein portion of the enzyme that provides the 3D tertiary structure, substrate-binding pocket, and catalytic active site framework.
• Co-factor: The non-protein constituent bound to the enzyme to make it catalytically active.

Step 2

Types of Co-factors

Distinguishing non-protein co-factors:

• Prosthetic group: An organic co-factor tightly and permanently bound to the apoenzyme (e.g. haem in catalase).
• Coenzyme: An organic co-factor only transiently associated with the apoenzyme during catalysis (often derived from vitamins, e.g. NAD, NADP from niacin).
• Metal ions: Inorganic co-factors coordinating with active site residues (e.g. $Zn^{2+}$ in carbonic anhydrase).

Step 3

Conclusion

The protein portion of an enzyme is called the Apoenzyme.

\text{Holoenzyme} = \underbrace{\text{Apoenzyme}}_{\text{Protein portion}} + \underbrace{\text{Co-factor}}_{\text{Non-protein portion}}

⭐

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 A

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. A cofactor is the NON-PROTEIN constituent required for enzyme activity.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing non-protein cofactor with protein portion.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Coenzymes are organic non-protein cofactors (often vitamin derivatives like NAD).

⚠️

Student Fallacy (Why candidates pick this trap): Equating coenzymes with the protein polypeptide chain.

3 C

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. Direct verbatim NCERT definition: "the protein portion of the enzymes is called the apoenzyme".

💡

Why this is airtight: None; textbook recall.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. A prosthetic group is a tightly bound organic non-protein cofactor.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing the prosthetic group with the apoenzyme.

⚠️

NTA Trap Alert: Apoenzyme vs Coenzyme

Apoenzyme is the PROTEIN. Coenzyme is the NON-PROTEIN organic helper (vitamin). "Apo" means "away/detached from cofactor".

🛡️ How to avoid the -1 mark: Apo = Amino acid polymer = Protein!

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Core NEET Syllabus Standard

NEET Biology Core Syllabus · Biomolecules Standard Benchmark

Core Scientific Principle Tested:

"In a holoenzyme, the protein portion is termed the apoenzyme, which is catalytically inactive without its specific co-factor."

Syllabus Focus: Enzymes · Co-factors (Apoenzyme)

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

APO-enzyme = All-Protein Original!

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

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NEET 2025 Zoology Question 149 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Enzyme Terminology Equation Fingerprint

Step-by-Step Rigorous Workflow & Mathematical Proof

Composition of Conjugated Enzymes (Holoenzymes)

Types of Co-factors

Conclusion

360° Option Elimination Engine Key Feature

NTA Trap Alert: Apoenzyme vs Coenzyme

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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