What is the basic structural arrangement of a cell membrane?

The cell membrane's basic structural arrangement is best described as a phospholipid bilayer with embedded proteins. The phospholipid bilayer consists of two layers of phospholipid molecules, which have hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails. This unique organization allows the cell membrane to be semi-permeable, controlling the movement of substances in and out of the cell.

The proteins embedded within this bilayer serve various functions, such as facilitating transport, acting as receptors for signaling, and providing structural support. These proteins can be integral, spanning the membrane, or peripheral, lying on the inner or outer surfaces. This composition is crucial for maintaining the integrity and functionality of the cell, allowing it to interact with its environment effectively.

The other options do not accurately represent the structure of the cell membrane. A single lipid layer would not be stable enough to form a protective barrier. A protein layer surrounding lipids reverses the foundational understanding of membrane structure, while a rigid carbohydrate layer does not correspond to the fluid and dynamic nature of cell membranes. Thus, the phospholipid bilayer model with embedded proteins is integral to the cell's overall functionality and structural integrity.