The correct sequency of flow of electons in the light reaction is

Options

A. PSII, plastoquinone, cytochromes, PSI, ferredoxin
B. PSI, plastoquinone, cytochromes, PSII, ferredoxin
C. PSI, ferredoxin, PSII
D. PSI,plastoquinone, cytochromes, PSII, ferredoxin.

Explanation

To answer the question regarding the correct sequence of the flow of electrons in the light reaction of photosynthesis, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Light Reaction**: The light reaction occurs in the thylakoid membranes of chloroplasts and requires light energy. It involves the absorption of light by chlorophyll and the subsequent conversion of that energy into chemical energy.

2. **Photon Absorption**: The process begins when photons (light particles) are absorbed by chlorophyll molecules in Photosystem II (PSII). This energy excites electrons, raising them to a higher energy state.

3. **Water Splitting (Photolysis)**: The excited electrons from PSII are replaced by electrons derived from the splitting of water molecules (H2O). This process releases oxygen (O2) as a byproduct.

4. **Electron Transport Chain**: The high-energy electrons from PSII are then transferred to an electron transport chain (ETC). As the electrons move through the ETC, they lose energy, which is used to pump protons (H+) into the thylakoid lumen, creating a proton gradient.

5. **Photosystem I (PSI)**: The electrons eventually reach Photosystem I (PSI), where they are re-excited by light energy absorbed by PSI.

6. **Formation of NADPH**: The re-excited electrons from PSI are then transferred to NADP+ (nicotinamide adenine dinucleotide phosphate), reducing it to NADPH. This molecule serves as a reducing agent in the Calvin cycle (dark reaction).

7. **ATP Formation**: Simultaneously, the proton gradient created during the electron transport is used by ATP synthase to convert ADP and inorganic phosphate (Pi) into ATP, another energy carrier.

### Final Sequence of Electron Flow:
1. **Chlorophyll in Photosystem II absorbs light →**
2. **Electrons are excited and transferred to the electron transport chain →**
3. **Water is split to replace lost electrons →**
4. **Electrons move through the electron transport chain →**
5. **Electrons reach Photosystem I and are re-excited →**
6. **Electrons reduce NADP+ to NADPH →**
7. **ATP is produced via ATP synthase using the proton gradient.**

### Summary:
The correct sequence of the flow of electrons in the light reaction is:
1. Photosystem II (PSII) →
2. Electron Transport Chain →
3. Photosystem I (PSI) →
4. NADP+ (to form NADPH) and ATP synthesis.