What is a key feature of the phospholipid bilayer?

The phospholipid bilayer is a fundamental component of cell membranes and is characterized by its flexibility and selective permeability. This means that while the bilayer is structured to form a barrier, it is not rigid; rather, it allows for some movement and fluidity, which is essential for the functioning and adaptability of the cell.

The selective permeability aspect refers to the ability of the bilayer to control which substances can enter or leave the cell. Only certain molecules, such as small nonpolar molecules, can pass freely through the bilayer, while larger or polar molecules require specific transport mechanisms or proteins embedded in the membrane to facilitate their movement. This selectivity is crucial for maintaining the internal environment of the cell, allowing it to regulate its composition and respond to changes in the external environment.

This characteristic of being flexible and selectively permeable is vital for various cellular processes, including signaling, nutrient uptake, and waste removal, thereby contributing to the overall health and function of the organism.