The role of phospholipids in a cell membrane is crucial for maintaining the structure and function of cells. Phospholipids form a bilayer, with hydrophilic (water-attracting) heads facing outward and hydrophobic (water-repelling) tails facing inward. This arrangement creates a semi-permeable membrane that regulates the movement of substances into and out of the cell, facilitating communication and signaling. Additionally, phospholipids contribute to the membrane's fluidity, allowing for the mobility of proteins and other components essential for cellular processes, such as transport and cell recognition.