Question 74:
A substance that receives electrons in an oxidation-reduction reaction is called:
In oxidation-reduction reactions, the substance that receives electrons is called the electron acceptor.
Correct Answer
(A) Electron acceptor
Core Concept
In redox reactions, electrons transfer from donor (oxidized) to acceptor (reduced). The electron acceptor gains electrons, becoming reduced—think O₂ → H₂O in respiration. This drives metabolism, photosynthesis, and bioenergetics.
Option Analysis
| Option | Role | Correct/Incorrect | Example |
|---|---|---|---|
| (A) Electron acceptor | Receives electrons (reduced) | ✅ Correct | O₂ + 4e⁻ + 4H⁺ → 2H₂O |
| (B) Electron donor | Gives electrons (oxidized) | ❌ Wrong | NADH → NAD⁺ + H⁺ + 2e⁻ |
| (C) Electron carrier | Transports electrons | ❌ Wrong | Cytochrome c, ubiquinone |
| (D) Eluate | Chromatography fraction | ❌ Wrong | Purified protein solution |
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(A) Correct: By definition, accepts electrons in redox reactions (oxidizing agent).
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(B) Wrong: Opposite—loses electrons (reducing agent).
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(C) Wrong: Intermediates like ETC components shuttle electrons between donor/acceptor.
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(D) Wrong: Biochemistry term for column chromatography eluent, unrelated to redox. [context]
Biological Examples
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Respiration: O₂ (acceptor) ← electrons ← Complex IV
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Photosynthesis: NADP⁺ (acceptor) ← electrons ← ferredoxin
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Anaerobic: NO₃⁻, SO₄²⁻ serve as alternative acceptors
GATE tip: “Receives electrons” = acceptor; “loses electrons” = donor. Perfect discriminator!
The substance that receives electrons in an oxidation-reduction reaction is the electron acceptor, fundamental to bioenergetics and GATE Life Sciences metabolism questions.
Redox Reaction Fundamentals
Oxidation-reduction (redox) reactions involve electron transfer:
Reductant (donor) → Oxidant (acceptor) + e⁻
Electron acceptor gains electrons, gets reduced. Critical for ATP synthesis via electron transport chain (ETC).
Complete Option Breakdown
| Term | Definition | Role in Redox | GATE Relevance |
|---|---|---|---|
| Electron acceptor | Gains e⁻, becomes reduced | Final electron destination | Correct answer |
| Electron donor | Loses e⁻, becomes oxidized | Electron source | Common distractor |
| Electron carrier | Shuttles e⁻ between complexes | ETC intermediates | Ubiquinone, cyt c |
| Eluate | Solution from chromatography | Protein purification | Biochemistry lab |
Electron acceptor examples: O₂ (aerobic respiration), NO₃⁻ (denitrification), CO₂ (methanogenesis).
Electron Transport Chain Flow
NADH → Complex I → Q → Complex III → Cyt c → Complex IV → **O₂ (acceptor)**
Final acceptor (O₂) has highest reduction potential, making ΔG negative (energy-releasing).
Why “Eluate” Tricks Students
“Eluate” sounds biochemical but belongs to column chromatography (affinity, ion-exchange), not redox. Classic GATE misdirection testing terminology precision. [context]
Exam Strategy
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Receives electrons = acceptor (reduced)
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Loses electrons = donor (oxidized)
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Carries electrons = carrier (shuttles)
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Exam pattern: Always test acceptor/donor distinction
Master substance receives electrons oxidation-reduction reaction = electron acceptor for guaranteed biochemistry scores!
