Whole scheme of transfer of electrons , starting from the PS II, uphill to the acceptor, down the electron transport chain to PS I ,excitation of elecitations, transfer to another acceptor, and finally down hill to NADP+ causing it to be reducedd to `NADPH +H^(+)` is called

Options

A. Oxidative phosphorylation
B. Cycllic photophosphorylation
C. PCR cycle
D. Z-scheme

Answer

**Step-by-Step Solution:**

1. **Understanding the Process**: The question describes a series of electron transfers that occur during photosynthesis, specifically from Photosystem II (PS II) to Photosystem I (PS I), and ultimately to NADP+.

2. **Starting at PS II**: The process begins at PS II, where light energy is absorbed, exciting electrons. These electrons are then transferred uphill to an electron acceptor.

3. **Electron Transport Chain**: The excited electrons move down an electron transport chain, which consists of various proteins, including cytochromes. This chain facilitates the transfer of electrons from PS II to PS I.

4. **Excitation at PS I**: When the electrons reach PS I, they are again excited by light energy. This excitation allows the electrons to be transferred to another acceptor molecule.

5. **Reduction of NADP+**: Finally, the electrons are transferred downhill to NADP+, reducing it to NADPH and releasing a proton (H+). This reduction is crucial for the synthesis of glucose during the Calvin cycle.

6. **Naming the Process**: The entire scheme of electron transfer described is known as the **Z scheme**. This name comes from the zig-zag shape of the energy graph that illustrates the energy changes during the process.

7. **Non-Cyclic Photophosphorylation**: It is important to note that this process is also referred to as non-cyclic photophosphorylation because the electrons lost from PS II are not returned; they are ultimately used to reduce NADP+.

8. **Conclusion**: Therefore, the answer to the question is that the whole scheme of electron transfer from PS II to NADP+ is called the **Z scheme**.

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