What forms the basic structure of the cell membrane?

The basic structure of the cell membrane is formed by phospholipids. These molecules consist of a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails." When placed in an aqueous environment, phospholipids arrange themselves into a bilayer, with the hydrophobic tails facing inward, away from water, and the hydrophilic heads facing outward towards the water both inside and outside the cell. This bilayer structure is fundamental to the cell membrane's function, as it creates a semi-permeable barrier that regulates the movement of substances into and out of the cell.

Proteins, while also critical parts of the cell membrane, are embedded within the phospholipid bilayer or attached to its surfaces, serving various functions such as transport, signaling, and structural support, but they do not form the fundamental bilayer structure itself. Nucleic acids, such as DNA and RNA, primarily are involved in genetic information storage and protein synthesis. Carbohydrates play key roles in cell recognition and signaling but do not contribute to the basic structural formation of the membrane. Thus, phospholipids are essential in establishing the cell membrane's architecture.