Which of the following cell organelles regulates the entry and exit of molecules to and from the cell?

The cell organelle that regulates the entry and exit of molecules to and from the cell is the cell membrane, also known as the plasma membrane. This semi-permeable barrier surrounds the cell and is composed of a lipid bilayer with embedded proteins, which play crucial roles in transport mechanisms.

The cell membrane allows certain molecules to pass through while blocking others, thereby maintaining homeostasis within the cell. Various transport processes are facilitated by the cell membrane, including passive transport (such as diffusion and osmosis), active transport (which requires energy to move substances against their concentration gradient), and bulk transport (such as endocytosis and exocytosis).

In summary, the cell membrane is essential for controlling the exchange of materials, nutrients, and waste products, ensuring that the internal environment of the cell is stable and optimal for cellular functions.