Which part of a cell performs each of the following functions :
Controls what enters and leaves the cell.

Explanation

**Step-by-Step Solution:**

1. **Identify the Function**: The function we need to address is controlling what enters and leaves the cell.

2. **Identify the Cell Part**: The part of the cell responsible for this function is the cell membrane.

3. **Understanding the Cell Membrane**: The cell membrane is described as semi-permeable or selectively permeable. This means it allows certain substances to pass while blocking others.

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