In prokaryotes, the membranes are relatively simple, but in eukaryotes, cell membranes contain various glycosphingolipids, sphingomyelin, chains of oligosaccharides and cholesterol in addition to phospholipids and phosphatidylcholine (lecithin). Cholesterol is also present, often at nearly a 1:1 ratio with the phospholipids in plasma membranes. Ref: Mescher A.L. (2010). Chapter 2. The Cytoplasm. In A.L. Mescher (Ed), Junqueira's Basic Histology: Text & Atlas, 12e.