Lipids: molecules composed predominantly of hydrogen and carbon atoms. (Brooker, 46) May contain other elements. A high energy source - two times that of “carbohydrates," and a long-term energy source. (Norton Lectures, 6/17/09)

Includes "fats," "phospholipids," and "steroids." Non-polar and therefore very “insoluble” in water. (Brooker, G-20) A broad class of biological compounds which are “soluble” in organic solvents such as "ethanol." but insoluble in water. (Hunt, 221) Lipids can only move in the "circulation" when bound to “proteins” to form large molecules called "lipoproteins." (Lewis, 133) Cells adapt to changes in temperature by altering the lipid composition of their “cellular membranes.” Most lipids can rotate freely around their long axes and move laterally within the cell membrane 'leaflet.' (Brooker, 88-89)


Eicosanoids: hormone-like substances that act near the site of “synthesis” without altering functions throughout the body. (MeSH) Lipids that cannot be synthesized by the body. (Norman, 6/17/09)

Leukotrienes: molecules that coordinate tissue response. Examples include ‘phagocytes’ (living white blood cells). (Norman, 6/17/09) Class of compounds released from 'mast cells' in local inflammatory reactions. They cause 'smooth muscle' contraction. (Lawrence)

Prostaglandins: molecules that direct local cellular activities. include chemicals that initiate an increase in body temperature to combat "microbes." Examples include ‘pyrogens.’ (Norman, 6/17/09) They participate in host defense reactions and … conditions such as immediate ‘hypersensitivity’ and “inflammation.” They have potent actions on many essential organs and systems, including the “cardiovascular,” pulmonary, and “central nervous system” as well as the gastrointestinal tract and the “immune system.” (MeSH)

Fats: a name usually given to "triglycerides" which are solid at temperatures below 20 degrees centigrade. (Indge) Glycerol plus a fatty acid chain. Saturated and unsaturated fats. (Norman, 27) Biological properties include long-term energy storage, protection for "organs," and insulations against temperature extremes. Fats are "hydrophobic." (Norman, 6/16/09) They contain "carbon," "oxygen," and "hydrogen," but no "nitrogen." Stored in animal cells where they provide a concentrated source of energy. When energy is required, fats are "hydrolysed" by "lipases" to fatty acids and glycerol, and the fatty acids are "metabolized" in the "mitochondria." (Lawrence)

Saturated Fatty Acids: fatty acids that do not have "double bonds" in the "hydrocarbon" chain. (Hunt, 148) The quality of a lipid when only single bonds are formed. Fat saturated with hydrogen. Solid at room temperature. Examples include butter and lard. (Norman, 6/16/09) Most saturated fats come from animal food products, but some plant oils, such as palm and coconut oil, also contain high levels. Eating saturated fat increases the level of "cholesterol" in the "blood" and the risk of "heart disease." (NCIt) Also referred to as ‘saturated fat.’

Unsaturated Fatty Acids: fatty acids that have one or more double bonds. (Hunt, 148) The quality of a lipid when a double bond is formed (Brooker, G-38) Hydrogen is removed. Liquid at room temperature. Examples include vegetable oil. Omega-3 fatty acids are good for the body. (Norman, 6/16/09) Also referred to as ‘unsaturated fats.’

Polyunsaturated Fatty Acids: fatty acids with two or more double bonds in the chain. (Hunt, 148) The essential fatty acids ‘omega-3’ and ‘omega-6’ are polyunsaturated fatty acids. Dietary intake of some polyunsaturated fatty acids may have beneficial effects on “blood pressure,” serum lipids, and inflammation. (NCIt) Also referred to as ‘polyunsaturated fats.’

Flip-Flop: movement of lipids from one leaflet to the opposite 'leaflet.' Flip-flop is not spontaneous movement because the “polar head group” would pass through the hydrophobic region of the “bilayer.” Instead an “enzyme” uses “ATP” to flip phospholipids from one leaflet to the other. (Brooker, 88) Editor’s note - not to be confused with the (unacceptable in Hawaii) term for the open-toed sandal mostly worn by teenagers in the summer. The accepted term in Hawaii, where they are worn year-round, is ‘rubber slippers’ or simply ‘slippers.’

Glycolipid: a component of cell membranes. (Lawrence) A lipid that has carbohydrate attached to it. (Brooker, G-16) A lipid with 2 fatty acid chains attached to a carbohydrate-containing ‘head group’ that is found on the outer leaflet of the “plasma membrane.” (NCIt)

Lipid Anchors: intracellular "proteins" attached to lipids between leaflets. (Norton Lectures, 6/3/09) Involves the attachment of a lipid to an “amino acid” within a protein. (Brooker, 87) Any of the various types of lipids that are "covalently" linked to some proteins, and serve to attach them to the "cytoplasmic" side of the plasma membrane. (Lawrence) Also referred to as 'intrinsic membrane protein.’

Lipoproteins: a complex of lipid and protein. (Lawrence) Carry lipids in the blood to “tissues,” where they are used. (Also carry) lipids to the “liver,” where they are broken down into biochemicals that the body can excrete more easily. (Lewis, 133) Abnormalities in lipoprotein metabolism have been implicated in certain heart diseases. (NCIt)

Phospholipids: the most abundant lipids found in cellular membranes. (Broker, 85) Constituents of all tissues and organs, especially the brain. They are synthesized in the liver and small intestine and are involved in many of the body's metabolic processes. (OxfordMed) Characterized by a non-lipid group plus a “phosphate group," plus glycerol and fatty acid. They have hydrophobic tails and “hydrophilic” heads. They form semi-permeable membranes. They form ‘micelles’ that surround other molecules for digestion. (Micelles are inside cells, but not inside the nucleus). They participate in moving substances into a cell - “endocytosis” and moving substances out of a cell - “exocytosis.” (Norman, 6/16/09)

Steroids: a lipid molecule with a chemical structure containing four interconnected rings of carbon atoms. (Brooker, G-35) Cholesterol is a "precursor" to all steroids (you can’t get steroids without cholesterol). Functions include initiating sexual changes in the body, maintaining tissue metabolism, maintaining mineral balance, and "emulsifying" fats as “bile salts.” Synthesized in the “smooth ER,” and stored in the “golgi apparatus” for later use. (Norman, 6/17/09)

Triglycerides: a lipid consisting of three fatty acid molecules which are linked to a molecule of glycerol. (Indge, 275) Compounds of fatty acids with glycerol, which is an “alcohol” with three ‘OH’ groups. Includes animal fats and vegetable oils. "Soluble" in "organic" "solvents." (Hunt, 349)  Also referred to as ‘triacylglycerols.’