Which term describes the boundary that encloses the cell?

• A. Nuclear envelope
• B. Cell wall
• C. Cell membrane (plasma membrane)
• D. Endomembrane system

Answer: (C)

The boundary enclosing the cell is the cell membrane, also called the plasma membrane. It’s a phospholipid bilayer that forms the outer living barrier, controlling what enters and leaves the cell and helping maintain the internal environment. The nuclear envelope is a membrane around the nucleus inside the cell, not the whole cell. The cell wall exists in plants, fungi, and some bacteria and provides support, but the actual boundary of the cell is the membrane (the wall sits outside the membrane in those cells). The endomembrane system consists of internal membranes like the endoplasmic reticulum and Golgi apparatus involved in making and shipping materials, not the outer boundary.