Why are phospholipids, but not triacylglycerols, found in cell membranes?

Phospholipids constitute of hydrolysable lipids that possess a phosphorus atom. The different classes of phospholipids include phosphoacylglycerols and sphingomyelins.

The plant and animal cell membranes comprises of these phospholipids.

When subjected to hydrolysis, triacylglycerols constitute triesters that generate glycerol and three fatty acid molecules. Some common fatty acids found in triacylglycerols include lauric acid and stearic acid.

Phospholipids comprises of a polar(ionic) head and two nonpolar tails. These regions exhibit different attractive forces.

This permits phospholipids to create a bilayer with a central hydrophobic region that functions as a boundary to agents intersecting the cell membrane. The phospholipids comprises of an ionic head that links with the aqueous environment inside and outside the cell.

Triacylglycerols comprises of three polar, uncharged ester groups. These groups are not polar when compared to phospholipids. Triacylglycerols do not constitute an ionic head with nonpolar tails. Hence, they do not form a bilayer.

These are nonpolar C-C and C-H bonds. Therefore, they get repelled from the aqueous medium, leading them to become water-insoluble.