What is the dominant molecule in the cell membrane?

The dominant molecule in the cell membrane is phospholipids. Phospholipids are essential components that form the basic structure of the cell membrane, known as the phospholipid bilayer. This bilayer is composed of two layers of phospholipids, where the hydrophilic (water-attracting) "heads" face outward towards the aqueous environments, while the hydrophobic (water-repelling) "tails" face inward, away from water. This arrangement allows the membrane to act as a barrier, selectively allowing substances to enter and exit the cell while maintaining a stable internal environment.

Phospholipids not only provide structural integrity but also play a crucial role in fluidity and flexibility of the membrane, enabling the cell to maintain its shape and allowing movement of materials in and out. Additionally, proteins and cholesterol are embedded within this phospholipid bilayer and contribute to various functions, including transport, signaling, and structural support, but phospholipids overwhelmingly dominate in their quantity and essential role in membrane formation.