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Zorluk: ZorPlant Nutrition and Photosynthesis

During non-cyclic photophosphorylation in plant photosynthesis, light energy drives a sequential flow of electrons across the thylakoid membrane. What is the correct chronological sequence of physiological events occurring during this light-dependent stage from initial photon absorption to final electron reduction?

  1. 1Absorption of light photons by reaction center P680 in Photosystem II, exciting electrons to a high-energy primary electron acceptor.
  2. 2Enzymatic photolysis of water molecules at the oxygen-evolving complex to replenish missing electrons in P680, releasing protons into the thylakoid lumen.
  3. 3Passage of excited electrons through plastoquinone and the cytochrome b6fb_6f complex, pumping protons into the thylakoid lumen to create a chemiosmotic gradient.
  4. 4Re-excitation of electrons by light absorption at reaction center P700 in Photosystem I and their transfer to ferredoxin.
  5. 5Reduction of NADP+NADP^+ to NADPHNADPH by NADP+NADP^+ reductase on the stromal side of the thylakoid membrane using electrons from ferredoxin.

Cevap

The correct chronological sequence of non-cyclic photophosphorylation is: 1) Excitation of P680 in Photosystem II → 2) Photolysis of water to replace electrons → 3) Electron transport through cytochrome b6fb_6f complex creating a proton gradient → 4) Re-excitation at P700 in Photosystem I → 5) Reduction of NADP+NADP^+ to NADPHNADPH.
The non-cyclic light reaction (Z-scheme) begins with photon absorption at Photosystem II (P680). The loss of electrons from P680 triggers the enzymatic photolysis of water to replace those electrons. The released electrons move down an electron transport chain featuring the cytochrome b6fb_6f complex (generating a proton gradient), after which they reach Photosystem I (P700) where photon absorption re-excites them. Finally, ferredoxin passes the electrons to NADP+NADP^+ reductase to reduce NADP+NADP^+ to NADPHNADPH.

Adım Adım Çözüm

1
Identify the initiating trigger of non-cyclic photophosphorylation.
Photon absorption by P680 (Photosystem II) excites electrons to a primary electron acceptor.
Light absorption at PS II initiates the entire Z-scheme electron transport sequence.
2
Determine how electron deficiency in P680 is resolved.
Photolysis of water splits H2OH_2O into electrons, H+H^+ ions, and O2O_2, supplying replacement electrons to P680.
Oxidized P680 is a strong oxidizing agent that forces water splitting at the manganese-containing complex.
3
Trace the path of energized electrons from Photosystem II.
Electrons pass down the plastoquinone-cytochrome b6fb_6f-plastocyanin chain into Photosystem I.
This electron transport generates the proton motive force required for ATP synthesis via chemiosmosis.
4
Follow the fate of electrons upon reaching Photosystem I.
Electrons are re-excited by light absorption at P700 (Photosystem I) and transferred to ferredoxin.
PS I absorbs light energy to boost electrons to a redox potential high enough to reduce NADP+NADP^+.
5
Identify the final electron acceptor step.
NADP+NADP^+ reductase transfers electrons from ferredoxin and stromal protons to form NADPHNADPH.
Terminal reduction of NADP+NADP^+ stores chemical reducing power for subsequent use in the Calvin cycle.

Anahtar Kavram

Non-cyclic Photophosphorylation and Z-scheme Electron Transport
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Konular

Plant Nutrition and Photosynthesis

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