Q.136 Botany ⭐ 360° Option Elimination Active

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NEET 2021 Botany Question 136 Solution

Topic: Respiration in Plants · Official NTA Booklet Code M1

Question

Which of the following statements is incorrect?

(1)During aerobic respiration, role of oxygen is limited to the terminal stage.
(2)In ETC (Electron Transport Chain), one molecule of NADH+H+ gives rise to 2 ATP molecules, and one FADH2 gives rise to 3 ATP molecules.
(3)ATP is synthesized through complex V.
(4)Oxidation-reduction reactions produce proton gradient in respiration.

✓

Verified Against NTA Final Answer Key

Option (2) : In ETC (Electron Transport Chain), one molecule of NADH + H+ gives rise to 2 ATP molecules, and one FADH2 gives rise to 3 ATP molecules.

📚 Respiration in Plants Easy

📋 Given Parameters & Problem Setup

Process Aerobic cellular respiration & Electron Transport Chain (ETC)

Target Identify the incorrect statement

⚡

The 30-Second Exam Hall Shortcut: ⚡ 1 NADH = 3 ATP & 1 FADH2 = 2 ATP (The Inverted Ratio Trap!)

⏱️ Save ~20 seconds

According to NCERT energetics, oxidation of 1 NADH + H⁺ yields 3 molecules of ATP, while oxidation of 1 FADH₂ yields 2 molecules of ATP! Statement (2) inverted this ratio (claiming 2 ATP for NADH and 3 ATP for FADH₂), making it blatantly incorrect. Match Option (2)!

1 Check Statement (1): Oxygen is terminal electron acceptor; role is limited to terminal stage

\implies

TRUE.

2 Check Statement (2): In ETC, 1 NADH yields 2 ATP and 1 FADH2 yields 3 ATP

\implies

FALSE (NCERT stoichiometry: 1 NADH

\to

3 ATP, 1 FADH2

\to

2 ATP).

3 Check Statement (3): ATP synthase is Complex V

\implies

TRUE.

4 Check Statement (4): Redox electron flow pumps protons across inner mitochondrial membrane to create proton gradient

\implies

TRUE.

5 Match Option (2).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Respiration in Plants on ETS and Oxidative Phosphorylation.

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Stoichiometry of ATP Synthesis in the ETS

Electrons from $NADH + H^+$ are transferred to $O_2$ via Complexes I, III, and IV, pumping 10 protons across the inner mitochondrial membrane, whereas electrons from $FADH_2$ enter at Complex II, pumping 6 protons. As established in the canonical NCERT text:

\begin{aligned} \mathbf{1 \text{ NADH} + \text{H}^+} & \xrightarrow{\text{Oxidative Phosphorylation}} \mathbf{3 \text{ ATP Molecules}} \\[4pt] \mathbf{1 \text{ FADH}_2} & \xrightarrow{\text{Oxidative Phosphorylation}} \mathbf{2 \text{ ATP Molecules}} \end{aligned}

Step 2

Evaluation of Statement (2)

Statement (2) asserts that "one molecule of $NADH + H^+$ gives rise to $2\text{ ATP}$ molecules, and one $FADH_2$ gives rise to $3\text{ ATP}$ molecules". This swaps the canonical stoichiometry, making it the incorrect statement requested by the question.

Step 3

Verification of Remaining Statements

- Statement (1): Oxygen acts as the final hydrogen/electron acceptor only at the very end of the ETS (Complex IV) to form metabolic water. - Statement (3): ATP synthase is universally designated as Complex V. - Statement (4): The free energy liberated during redox electron transitions drives active proton pumping into the intermembrane space, generating the electrochemical proton gradient.

⭐

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:

This statement is TRUE. Oxygen acts exclusively as the terminal electron and proton acceptor at Complex IV.

⚠️

Student Fallacy (Why candidates pick this trap): Overlooking that oxygen has no role until the terminal cytochrome c oxidase step.

2 2

✓ 100% Correct

Verdict & Scientific Reason:

This statement is FALSE (and hence the correct answer). Canonical yield is 3 ATP per NADH and 2 ATP per FADH2.

💡

Why this is airtight: None. Directly detects the inverted numerical stoichiometry.

3 3

✗ Incorrect

Verdict & Scientific Reason:

This statement is TRUE. Complex V is the mitochondrial ATP synthase comprising $F_0$ and $F_1$ components.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing Complex V with electron carriers Complex I–IV.

4 4

✗ Incorrect

Verdict & Scientific Reason:

This statement is TRUE. Chemiosmotic proton translocation is directly powered by redox reactions across Complexes I, III, and IV.

⚠️

Student Fallacy (Why candidates pick this trap): Thinking the proton gradient is generated by substrate-level phosphorylation.

⚠️

NTA Trap Alert: Swapped Number Trap (3 vs 2 ATP)

NTA loves switching the coefficients: 1 NADH = 3 ATP; 1 FADH2 = 2 ATP. Candidates rushing through the question miss the transposed numbers.

🛡️ How to avoid the -1 mark: Fix the rule: "NADH enters earlier at Complex I

\implies

3 ATP; FADH2 enters later at Complex II

\implies

2 ATP".

📖

Core NEET Syllabus Standard

NEET / NCERT Biology · Respiration in Plants Standard Benchmark

Core Scientific Principle Tested:

"Oxidation of one molecule of NADH gives rise to 3 molecules of ATP, while that of one molecule of FADH2 produces 2 molecules of ATP."

Syllabus Focus: Electron Transport System (ETS) and Oxidative Phosphorylation

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2021 Botany Question 136 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ 1 NADH = 3 ATP & 1 FADH2 = 2 ATP (The Inverted Ratio Trap!)

Step-by-Step Rigorous Workflow & Mathematical Proof

Stoichiometry of ATP Synthesis in the ETS

Evaluation of Statement (2)

Verification of Remaining Statements

360° Option Elimination Engine Key Feature

NTA Trap Alert: Swapped Number Trap (3 vs 2 ATP)

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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