The correct answer is (4): B, C, and D.

• B. P700 can receive electrons from plastocyanin
  Correct. Plastocyanin (PC) transfers electrons from the cytochrome b6f complex to P700 in PSI during light reactions.​

• C. NADPH is produced at the end of light reaction
  Correct. NADPH, along with ATP, is produced at the end of the light-dependent electron transport chain, specifically after electron transfer through PSI.​

• D. The hydrogen ions produced during light reaction gets concentrated in thylakoid lumen
  Correct. During electron transport, water splitting, and proton pumping, hydrogen ions (protons) accumulate within the thylakoid lumen and establish the gradient used by ATP synthase.​

• A. Electron from P680 moves first to quinone and then to the pheophytin
  Incorrect. The correct path is P680* (excited) passes electrons first to pheophytin (primary acceptor), then to quinone (QA), not the other way around.​

Light Reaction Electron Transport: Facts and Errors

Introduction

Key phrase: electron transport chain light reaction ATP NADPH thylakoid lumen PSI plastocyanin

Understanding the correct sequence of electron flow, proton movement, and product formation in chloroplasts is essential for mastering plant bioenergetics and photosynthesis.​

Explanation of Each Statement

• A. Electron from P680 moves first to quinone and then to the pheophytin

  • Incorrect. Pheophytin is the immediate electron acceptor after light excites P680; electrons then move to quinone QA.​

• B. P700 can receive electrons from plastocyanin

  • Correct. Plastocyanin is the mobile copper protein that donates electrons to the reaction center chlorophyll of PSI (P700).​

• C. NADPH is produced at the end of light reaction

  • Correct. NADP+ is reduced to NADPH after electrons pass through PSI and ferredoxin-NADP+ reductase.​

• D. The hydrogen ions produced during light reaction gets concentrated in thylakoid lumen

  • Correct. Water photolysis and electron transport cause protons to accumulate in the thylakoid lumen, generating the gradient for ATP synthesis.​

Key Facts: Photosynthetic Electron Transport Chain

• Electron flow: P680 → Pheophytin → Quinone (QA) → PQ → Cytochrome b6f → PC → P700, then PSI and NADPH production.​

• Proton gradient: Generated in thylakoid lumen powers ATP synthase.

• Plastocyanin transfers electrons to P700 for continued transport and reduction of NADP+.​