Advanced Placement (AP) Biology Practice Exam

What is the primary role of the plasma membrane in cellular function?

1. Protein synthesis

2. Energy production

3. Regulation of substances entering and exiting the cell

4. Genetic information storage

The correct answer is: Regulation of substances entering and exiting the cell

The primary role of the plasma membrane in cellular function is to regulate what substances enter and exit the cell. This selective permeability is crucial for maintaining homeostasis within the cell, allowing it to control its internal environment in response to changes outside the cell. The plasma membrane consists of a lipid bilayer with embedded proteins that facilitate the transport of molecules. Proteins can function as channels or carriers to move specific substances across the membrane, while other proteins serve as receptors that can trigger signaling pathways in response to external signals. Additionally, the plasma membrane plays a vital role in communication between cells, recognition of cellular signals, and maintaining the structural integrity of the cell. By carefully controlling the movement of ions, nutrients, and waste products, the plasma membrane helps maintain the appropriate chemical composition and overall function necessary for the survival of the cell.