Which statement best describes the structure of the plasma membrane?

The statement that describes the structure of the plasma membrane as a phospholipid bilayer is accurate and reflects the fundamental architecture of the membrane. The plasma membrane is primarily composed of two layers of phospholipids, with their hydrophobic (water-repelling) tails facing inward and their hydrophilic (water-attracting) heads facing outward towards the extracellular fluid and the cytoplasm. This bilayer arrangement creates a semi-permeable barrier that is essential for cellular function.

The phospholipid bilayer allows for the fluidity of the membrane and supports the embedding of various proteins, cholesterol, and carbohydrates, all of which contribute to its function in transport, signaling, and maintaining homeostasis. The fluid mosaic model further describes how these components are not static but rather move laterally within the layer, enhancing the dynamic nature of the plasma membrane.

Understanding that the plasma membrane is structured as a bilayer is crucial because it underpins many biological processes, including selective permeability, communication between cells, and the interaction with the environment.