Q.154 Zoology ⭐ 360° Option Elimination Active

NEET 2023 Zoology Question 154 Solution

Topic: Biomolecules · Official NTA Booklet Code G5

Question

Given below are two statements: Statement I: A protein is imagined as a line, the left end represented by first amino acid (C-terminal) and the right end represented by last amino acid (N-terminal) Statement II: Adult human haemoglobin, consists of 4 subunits (two subunits of a type and two subunits of B type.) 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 (1) : Statement I is false but Statement II is true.

📚 Biomolecules Medium

📋 Given Parameters & Problem Setup

Statement I Left end of protein line is C-terminal and right end is N-terminal.

Statement II Adult human haemoglobin consists of 4 subunits (two of α type and two of β type).

⚡

The 30-Second Exam Hall Shortcut: ⚡ Protein Polarity Rule: Left is N-terminal, Right is C-terminal!

⏱️ Save ~25 seconds

By international biochemical convention and verbatim NCERT: the left end of a polypeptide is the first amino acid (N-terminal) and the right end is the last amino acid (C-terminal). Statement I inverts this and is FALSE! Statement II is TRUE ( $2\alpha 2\beta$ ). Select Option (1)!

1 Check Statement I: NCERT states left end is first amino acid (N-terminal) and right end is last amino acid (C-terminal) -> Statement I inverts them -> False.

2 Check Statement II: Adult human haemoglobin consists of 4 subunits: 2 alpha and 2 beta (

2\alpha 2\beta

) -> True.

3 Statement I is false but Statement II is true.

4 Match Option (1).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Biomolecules polypeptide directional nomenclature and oligomeric protein architecture.

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Evaluation of Statement I (Polypeptide Polarity Convention)

Polypeptides are synthesized in the $N \to C$ direction from the ribosome. NCERT defines the positional convention of a primary protein structure:

\text{Polypeptide Line:} \quad \mathbf{\text{Left End: N-terminal (First Amino Acid)}} \longleftrightarrow \mathbf{\text{Right End: C-terminal (Last Amino Acid)}}

Step 2

Verbatim NCERT Reference for Statement I

NCERT states verbatim: "A protein is imagined as a line, the left end represented by the first amino acid and the right end represented by the last amino acid. The first amino acid is also called as N-terminal amino acid. The last amino acid is called the C-terminal amino acid." Because Statement I claims the left end is C-terminal and right end is N-terminal, it is definitively FALSE.

Step 3

Evaluation of Statement II (Haemoglobin Quaternary Structure)

Adult human hemoglobin ( $HbA$ ) is an allosteric tetrameric metalloprotein:

\text{Adult Haemoglobin (HbA)} = 2\alpha + 2\beta = \mathbf{4\text{ Subunits}} \implies \text{Statement II is } \mathbf{\text{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

✓ 100% Correct

Verdict & Scientific Reason:

Statement I inverts the N-terminal/C-terminal positions; Statement II accurately describes the 2α 2β tetrameric subunit structure of adult haemoglobin.

💡

Why this is airtight: None; rigorous biochemical literacy.

2 2

✗ Incorrect

Verdict & Scientific Reason:

Statement I is false due to inverted directional nomenclature.

⚠️

Student Fallacy (Why candidates pick this trap): Reading Statement I carelessly and assuming left-to-right terminus order is correct without checking N vs. C.

3 3

✗ Incorrect

Verdict & Scientific Reason:

Statement II is factually true.

⚠️

Student Fallacy (Why candidates pick this trap): Doubting whether adult haemoglobin contains 2 alpha and 2 beta subunits.

4 4

✗ Incorrect

Verdict & Scientific Reason:

Both statement truth values are completely reversed.

⚠️

Student Fallacy (Why candidates pick this trap): Inverting both biochemical concepts.

⚠️

NTA Trap Alert: N-terminal vs. C-terminal Polarity Inversion Trap

NTA intentionally reversed "N-terminal" and "C-terminal" in Statement I. Students who skim the text remember that "first and last amino acids are at ends" and miss the polarity flip.

🛡️ How to avoid the -1 mark: Always remember: Proteins read left-to-right like reading English: N-terminal first (left), C-terminal last (right).

📖

Core NEET Syllabus Standard

NCERT Biology · Biomolecules Standard Benchmark

Core Scientific Principle Tested:

"Left end of protein is the first amino acid (N-terminal) and right end is the last amino acid (C-terminal). Adult hemoglobin consists of 4 subunits (2 alpha and 2 beta)."

Syllabus Focus: Structure of Proteins

✓ 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 154 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Protein Polarity Rule: Left is N-terminal, Right is C-terminal!

Step-by-Step Rigorous Workflow & Mathematical Proof

Evaluation of Statement I (Polypeptide Polarity Convention)

Verbatim NCERT Reference for Statement I

Evaluation of Statement II (Haemoglobin Quaternary Structure)

360° Option Elimination Engine Key Feature

NTA Trap Alert: N-terminal vs. C-terminal Polarity Inversion Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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