Final answer:
Lipids in cell membranes include triglycerides (fats and oils), waxes, phospholipids, and steroids. Phospholipids, with their hydrophilic heads and hydrophobic tails, form the bilayer structure of membranes, while steroids like cholesterol help maintain membrane fluidity.
Step-by-step explanation:
Lipids are a diverse group of macromolecules essential to cell membrane structure and function. The major types of lipids found in cellular membranes include fats and oils, waxes, phospholipids, and steroids. Fats and oils, also known as triglycerides, consist of glycerol or sphingosine bonded to three fatty acids, which can be saturated (no double bonds) or unsaturated (one or more double bonds). Waxes provide a protective, water-resistant layer. Phospholipids form the key structural components of the membrane, with a glycerol or sphingosine backbone, two fatty acid chains, and a phosphate group. They are arranged in a bilayer, with hydrophobic tails inside and hydrophilic heads facing the watery exterior and interior of the cell. Finally, steroids like cholesterol have a structure based on four fused carbon rings and stabilize the membrane's fluid nature.