Final answer:
The cell membrane regulates which materials enter/exit the cell and protects the cell structurally.
Step-by-step explanation:
The main function of the cell membrane is to regulate which materials enter/exit the cell. It acts as a selective barrier, allowing certain substances to pass through while keeping others out. This process is crucial for maintaining the cell's internal environment and ensuring that it has the necessary nutrients and ions to function properly. Additionally, the cell membrane also plays a role in protecting the cell structurally, as it forms a boundary and helps maintain its shape.
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