What is the processes that creates proton gradient across thylakoid membrane ?

Options

A. Splitting of water molecule on inner side of membrane (towards lumen) .
B. H+ carrier transport H+ ion from stromal to lumen.
C. NADH reductase removes H+ ion from stroma for reduction of NADP+
D. All of the above processes

Answer

To solve the question regarding the processes that create a proton gradient across the thylakoid membrane, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding the Thylakoid Membrane**:
- The thylakoid membrane is part of the chloroplasts in plant cells where photosynthesis occurs. It plays a crucial role in the light-dependent reactions of photosynthesis.

2. **Photolysis of Water**:
- The first process that contributes to the proton gradient is the splitting of water molecules (H₂O) through a process called photolysis. This occurs in the lumen of the thylakoid membrane when chlorophyll absorbs light energy.
- **Result**: The photolysis of water produces oxygen (O₂), electrons (e⁻), and protons (H⁺). The protons are released into the lumen, increasing the concentration of hydrogen ions inside the thylakoid.

3. **Proton Transport by Hydrogen Ion Carriers**:
- The second process involves hydrogen ion carriers that transport protons from the stroma (the fluid outside the thylakoids) into the lumen of the thylakoid membrane.
- **Result**: This transport further increases the concentration of protons in the lumen, contributing to the proton gradient.

4. **Role of NADH Reductase**:
- The third process involves the enzyme NADH reductase, which removes hydrogen ions from the stroma for the reduction of NAD⁺ to NADH.
- **Result**: By removing protons from the stroma, this process helps maintain the proton gradient across the thylakoid membrane.

5. **Conclusion**:
- All three processes mentioned (photolysis of water, transport of hydrogen ions by carriers, and the action of NADH reductase) contribute to creating the proton gradient across the thylakoid membrane.
- Therefore, the correct answer to the question is **option 4: all of the above processes**.

### Final Answer:
The processes that create a proton gradient across the thylakoid membrane include:
1. Splitting of water molecules (photolysis).
2. Transport of hydrogen ions from stroma to lumen.
3. Action of NADH reductase removing hydrogen ions from the stroma.
Thus, the correct answer is **option 4: all of the above processes**.