The Question is from neet-botany , and it was created by the author K SURESH KUMAR

Question

Which one of the following is not a down hill movement of electrons is z – scheme?

K SURESH KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
**Primary Concept**: Electron transport in the Z-scheme of photosynthesis
**Related Topics**: Photosystems I and II, light-harvesting complexes, redox reactions, electron carriers
**Prerequisites**: Understanding of the Z-scheme and electron flow in photosynthesis
## SOLUTION PATHWAY
**Given Information**:
The question asks for the step that is *not* a downhill movement of electrons in the Z-scheme.
**Method & Steps**:
1. **Understand the Z-scheme**: The Z-scheme describes the path of electrons from water to NADP+ in photosynthesis. Downhill movement means electron transfer from a more negative redox potential to a more positive one.
2. **Analyze each option**: 
    *   **A. Pheophytin to PS-I**: Pheophytin is an electron acceptor in PSII. Electrons move from pheophytin to PS-I via a series of carriers, which is a downhill movement.
    *   **B. LHC-II to pheophytin**: Light-harvesting complex II (LHC-II) absorbs light energy and transfers it to the reaction center of PSII. This excitation of the reaction center allows the electrons to move from PSII to pheophytin. However, the energy transferred is not a downhill electron movement. The electron is excited to a higher energy level which is not a down hill movement. 
    *   **C. Ferredoxin to NADP+**: Ferredoxin transfers electrons to NADP+ reductase, which then reduces NADP+ to NADPH. This is a downhill movement.
3. **Identify the exception**: Option B represents the initial excitation event, not electron transfer from a reduced carrier to a more oxidized one. Therefore, it is not a downhill movement of electrons. 
4. **Select the answer**: Based on the analysis, option B is the correct answer. 
## OPTION ANALYSIS
[A] :x: Pheophytin to PSI is a downhill electron transfer.
[B] ✓: LHC-II to pheophytin is an excitation process, not a downhill electron transfer.
[C] :x: Ferredoxin to NADP+ is a downhill electron transfer.
[D] :x: Options A and C are both downhill movements. 
## LEARNING AIDS
**Common Mistakes**:
 1. Confusing excitation with electron transfer: Excitation is an energy transfer, not necessarily a movement of electrons to a lower energy level.
 2. Not understanding the Z-scheme: A clear understanding of the sequence and direction of electron flow is essential.
**Quick Tips**:
1. Visualize the Z-scheme: Draw a diagram to remember the order of electron carriers.
2. Remember that downhill movement means moving to a more positive redox potential.

K SURESH KUMAR · Answer

Pheophytin to PS – I

K SURESH KUMAR · Answer

The correct Option is "LHC – II to pheophytin "

K SURESH KUMAR · Answer

ferredoxin to $NAD{P^ + }$

K SURESH KUMAR · Answer

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