RT Book, Section A1 Janson, Lee W. A1 Tischler, Marc E. SR Print(0) ID 1152118257 T1 MEMBRANES T2 The Big Picture: Medical Biochemistry YR 2018 FD 2018 PB McGraw-Hill Education PP New York, NY SN 9780071637916 LK accessmedicine.mhmedical.com/content.aspx?aid=1152118257 RD 2024/03/28 AB Lipids, driven by their hydrophobic and hydrophilic portions, form the biological membranes found in all living creatures. These include the cell and nuclear membranes as well as membranes that are part of organelles such as mitochondria and the endoplasmic reticulum (ER). Membranes provide separation of different environments to permit a variety of biological functions. Membranes are not static structures: rather they are dynamic and fluid and allow selective movement of ions, energy sources, vitamins and cofactors, and waste. Complex lipids such as cholesterol and sphingolipids both affect the structure of membranes where they are found and are also involved in specific functions.