Which part of the cell is responsible for controlling what enters and exits the cell?

The part of the cell that controls what enters and exits the cell is the cell membrane. The cell membrane, also referred to as the plasma membrane, is a biological barrier that surrounds the cell, providing structure and protection. It is selectively permeable, meaning it allows certain substances to pass through while restricting others. This selective permeability is crucial for maintaining the cell's internal environment, allowing it to take in nutrients and remove waste products.

By regulating the movement of ions, molecules, and water in and out of the cell, the cell membrane plays a vital role in homeostasis, which is the balance of conditions within the cell necessary for proper functioning. The fluid nature of the membrane, allowing proteins and lipids to move laterally, also helps facilitate these functions by adjusting how substances can enter or exit based on the cell's needs.