State whether the following statement is true or false.
Membranes usually have a negative charge on their outer surface.
A. True
B. False

Answer

To determine whether the statement "Membranes usually have a negative charge on their outer surface" is true or false, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Membrane Structure**:
- Cell membranes are composed of a phospholipid bilayer with embedded proteins. The outer surface of the membrane faces the extracellular environment, while the inner surface faces the cytoplasm of the cell.

2. **Charge Distribution**:
- The distribution of charges across the membrane is crucial for various cellular functions, including signaling and maintaining the cell's resting potential.

3. **Identifying Charge Locations**:
- Typically, the inner surface (cytoplasmic side) of the membrane has a negative charge due to the presence of negatively charged molecules like phosphatidylserine and other anionic lipids.
- Conversely, the outer surface (extracellular side) of the membrane tends to have a positive charge due to the presence of cations and the overall composition of the extracellular fluid.

4. **Evaluating the Statement**:
- The statement claims that membranes usually have a negative charge on their outer surface. Based on the understanding of charge distribution, this is incorrect.
- Therefore, the correct answer to the statement is that it is **false**.

5. **Conclusion**:
- The correct option is B. False.

### Final Answer:
**B. False**

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