Plant and animal cells are surrounded by the plasma membrane. The main function of the plasma membrane is to

Options

A. control the movement of substances across the cell
B. control the cellular activities within the cell
C. carry out protein synthesis
D. carry out lipid synthesis

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks about the main function of the plasma membrane surrounding plant and animal cells.

2. **Understand the Plasma Membrane**: The plasma membrane, also known as the cell membrane, is a biological membrane that separates and protects the interior of all cells from the outside environment.

3. **Evaluate the Options**:
- **Option 1**: "To control the movement of substances across the cell."
- This option is correct because the plasma membrane is selectively permeable, meaning it regulates what enters and exits the cell.
- **Option 2**: "To control the cellular activities within the cell."
- This option is incorrect as the nucleus is responsible for controlling cellular activities, not the plasma membrane.
- **Option 3**: "To carry out protein synthesis."
- This option is also incorrect because protein synthesis occurs in the ribosomes and the rough endoplasmic reticulum, not the plasma membrane.
- **Option 4**: "To carry out lipid synthesis."
- This option is incorrect as lipid synthesis is primarily carried out by the smooth endoplasmic reticulum.

4. **Conclusion**: After evaluating all the options, the main function of the plasma membrane is to control the movement of substances across the cell, making **Option 1** the correct answer.

**Final Answer**: The main function of the plasma membrane is to control the movement of substances across the cell.

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