What is the main structural component of cell membranes?

Phospholipids are indeed the main structural component of cell membranes. They are amphipathic molecules, meaning they possess both a hydrophilic (water-attracting) head and hydrophobic (water-repelling) tails. This unique structure allows phospholipids to spontaneously arrange themselves into a bilayer when in an aqueous environment, with the hydrophilic heads facing outward towards the water and the hydrophobic tails facing inward, away from the water.

This bilayer structure is fundamental to the formation of cell membranes, providing a semi-permeable barrier that separates the internal environment of the cell from the external surroundings. The fluid mosaic model describes this arrangement, where phospholipids create a dynamic and flexible barrier that can accommodate proteins, carbohydrates, and cholesterol embedded within or attached to the membrane.

While triacylglycerides primarily function as energy storage molecules and play a role in lipid metabolism, they are not integral to membrane structure. Cholesterol contributes to membrane fluidity and stability but does not form the primary structural framework. Glycolipids, although important for cell recognition and signaling, also do not constitute the main structural component of membranes but rather serve supportive roles associated with the bilayer.