Which substance is crucial for the structural integrity of cell membranes?

Lecithin is a vital substance for the structural integrity of cell membranes because it is a type of phospholipid. Phospholipids are essential components of the cell membrane, forming a bilayer that provides both structural support and flexibility. The hydrophilic (water-attracting) heads of phospholipids face outwards towards the water inside and outside the cell, while the hydrophobic (water-repelling) tails face inward, away from water. This arrangement creates a semi-permeable membrane that regulates the movement of substances in and out of the cell, maintaining homeostasis. Lecithin, which is rich in phospholipids, plays a key role in maintaining healthy cell membranes and facilitating cellular functions.

While cholesterol also contributes to membrane structure by providing stability and fluidity, lecithin is more directly associated with the formation of the membrane itself. Glucose is primarily an energy source for cells, and phosphorus, while it is a component of nucleic acids and energy-carrying molecules like ATP, does not play a direct role in the structural makeup of cell membranes.