Mobile electron carriers attached loosely to the thylakoid membrane towards lumen side

Options

A. OEC
B. PQ
C. PC
D. Fd

Answer

To answer the question about the mobile electron carriers attached loosely to the thylakoid membrane towards the lumen side, we will analyze the options provided and determine the correct one step by step.

### Step-by-Step Solution:

1. **Understanding the Thylakoid Membrane**: The thylakoid membrane is a crucial component of chloroplasts in higher plants where photosynthesis occurs. It contains various proteins and complexes involved in the light-dependent reactions.

**Hint**: Recall that the thylakoid membrane is where light energy is converted into chemical energy.

2. **Identifying Mobile Electron Carriers**: Mobile electron carriers are molecules that transport electrons between different complexes in the thylakoid membrane. They are essential for the electron transport chain during photosynthesis.

**Hint**: Think about how electrons move from one protein complex to another in the light-dependent reactions.

3. **Analyzing the Options**:
- **Option 1: OEC (Oxygen Evolving Complex)**: This complex is involved in water splitting and oxygen production but is not a mobile electron carrier.

**Hint**: Consider the function of OEC and whether it transports electrons.

- **Option 2: PQ (Plastoquinone)**: While PQ is involved in the electron transport chain, it is not specifically described as being loosely attached to the lumen side of the thylakoid membrane.

**Hint**: PQ is a mobile carrier but check its attachment and location carefully.

- **Option 3: PC (Plastocyanin)**: This is a copper-containing protein that acts as a mobile electron carrier and is indeed loosely attached to the thylakoid membrane towards the lumen side.

**Hint**: Look for the carrier that is known for its role in transferring electrons from PSII to PSI.

- **Option 4: FD (Ferredoxin)**: This protein is involved in transferring electrons but is associated with PSI and not specifically with the lumen side of the thylakoid membrane.

**Hint**: Remember the role of FD in the electron transport chain and its location.

4. **Conclusion**: After analyzing all options, it is clear that **PC (Plastocyanin)** is the correct answer as it is a mobile electron carrier that is loosely attached to the thylakoid membrane towards the lumen side.

### Final Answer:
**PC (Plastocyanin)** is the mobile electron carrier attached loosely to the thylakoid membrane towards the lumen side.