text: what are the structural differences between phospholipids and triglycerides? this is a cell and molecular biology class.  i need as much detail as possible please.  thank you. trigylcerides are composed of two types of molecules: glycerol and 3 fatty acids.  phospholipids are similar to triglycerides in that they contain glycerol and fatty acids, too. but, the big difference is that phospholipids are made up of 1 glycerol molecule and only 2 fatty acid molecules (not 3!)  this is a big difference because in place of the third fatty acid, phospholipids have a polar group attached to the glycerol molecule. remember, triglycerides were entirely hydrophobic because all three positions on the glycerol molecule were taken up by nonpolar fatty acids. but, phospholipids have a polar group in one place on the glycerol molecule, making phospholipids partly hydrophilic; the polar group helps to form the polar head.  the two fatty acids, maintain a hydrophobic portion of the phospholipid, the tails.