Appendix to Chapter 1 Cholesterol, saturated, and unsaturated fats. What do they do in the body?

Abstract Membranes encircle all cells and control the exchange of material between the cell and its surroundings. Inside cells, membranes separate the different cell compartments (organelles, such as nucleus and mitochondria) from the fluid cell matrix (the cytosol). The main constituents of membranes are lipid and protein, the amount of protein increasing with the number of functions the membrane performs. ‘ Lipid’ is a general term used to describe any biological compound that is soluble in organic solvents such as chloroform and ether. The term includes both molecules that contain fatty acids, examples being triglycerides and phospholipids, and molecules containing hydrocarbon ring structures, examples being cholesterol, steroid hormones, and some of the fat-soluble vitamins.