What structure encloses the cytoplasm of a cell and is semipermeable?

The cell membrane, also known as the plasma membrane, is the structure that encloses the cytoplasm of a cell and is semipermeable. This means that it selectively allows certain substances to pass in and out of the cell while blocking others. The cell membrane is composed of a lipid bilayer with embedded proteins, which facilitate transport processes and cell communication.

The semipermeable nature of the cell membrane is essential for maintaining homeostasis within the cell, as it regulates the internal environment by controlling the movement of ions, nutrients, and waste products. It plays a critical role in processes such as osmosis and diffusion, ensuring that the cell can maintain optimal conditions for its metabolism and overall function.

Other structures mentioned, such as the nucleus, Golgi body, and mitochondria, serve specific functions within the cell but do not enclose the cytoplasm or serve as a selective barrier. The nucleus houses genetic material, the Golgi body is involved in modifying and packaging proteins, and mitochondria are responsible for energy production. Hence, they do not possess the semipermeable properties characteristic of the cell membrane.