AEMCA Practice Exam

What role does the cell membrane play in the functioning of a cell?

1. It generates energy

2. It selectively allows substances to enter and exit

3. It stores genetic information

4. It synthesizes proteins

The correct answer is: It selectively allows substances to enter and exit

The role of the cell membrane in the functioning of a cell is primarily that it selectively allows substances to enter and exit. This selective permeability is crucial for maintaining the internal environment of the cell, allowing it to control which molecules can enter or leave. The cell membrane is composed of a phospholipid bilayer with embedded proteins, which facilitates this selective transport. For instance, certain proteins act as channels or transporters that enable specific ions or molecules to pass through, while keeping others out, thus regulating the internal concentration of various substances. This function is vital for processes such as nutrient intake, waste excretion, and cell signaling. This selective permeability is distinct from the roles associated with the other options. Generating energy is primarily the function of mitochondria, which convert nutrients into usable energy forms, while genetic information is stored in the nucleus, and proteins are synthesized by ribosomes in the cytoplasm. Therefore, the cell membrane's ability to manage the movement of materials is critical for cellular homeostasis and overall function.