Kaplan Nursing Entrance Practice Exam

What is the primary function of the cell membrane?

1. To produce energy for the cell

2. To regulate the passage of materials into and out of the cell

3. To store genetic information

4. To provide rigidity to the cell

The correct answer is: To regulate the passage of materials into and out of the cell

The primary function of the cell membrane is to regulate the passage of materials into and out of the cell. This selective permeability is crucial for maintaining the internal environment of the cell, allowing it to control what substances can enter or leave. The cell membrane consists of a phospholipid bilayer embedded with various proteins that facilitate the transport of molecules, ensuring that essential nutrients can enter the cell while waste products are removed effectively. The other functions mentioned, while important for overall cell function, do not describe the primary role of the cell membrane. Producing energy is a function associated with mitochondria, storing genetic information is primarily handled by the nucleus, and providing rigidity is more characteristic of the cell wall in plant cells, while the cell membrane contributes more to fluidity and flexibility.