What is the main function of the phospholipid bilayer in the cell membrane?

• A. To provide structure and selective permeability, controlling what enters and leaves the cell
• B. To generate energy
• C. To store genetic information
• D. To synthesize proteins

Answer: (A)

The phospholipid bilayer forms a selective boundary that provides structure and regulates what can enter or leave the cell. Its amphipathic arrangement creates a stable barrier: the hydrophobic interior blocks most water-soluble substances, while membrane proteins and channels allow selective transport, keeping the cell’s internal environment stable. This combination gives the membrane both shape and control over movement, which is essential for maintaining homeostasis and enabling signaling and transport functions. Energy production happens in mitochondria, genetic information is stored in DNA, and protein synthesis is carried out by ribosomes, so those roles belong to other cellular components rather than the phospholipid bilayer itself.