*Fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others.
*Bio functions of lipids = energy storage, as structural components of cell membranes, and as signaling molecules.
*Steroids occur in animals in hormones. Four-ring structure, one with five carbons and three with six carbons in the rings.
*Fat = a triglyceride. Made up of glycerol connected to one, two, or three fatty acids. Glycerol is the basis of all fats and is made up of a three-carbon chain. It connects the fatty acids together. A fatty acid is a long chain of carbon atoms connected to each other.
There are two kinds of fats, saturated and unsaturated. Unsaturated fats have at least one double bond in one of the fatty acids. A double bond happens when two electrons are shared or exchanged in a bond. They are much stronger than single bonds. Saturated fats have no double bonds.
Fats have a lot of energy stored up in their molecular bonds. That's why the human body stores fat as an energy source. When it needs extra fuel, your body breaks down the fat and uses the energy. Where one molecule of sugar only gives a small amount of energy, a fat molecule gives off many times more.
All Lipids are hydrophobic: that’s the one property they have in common.
Fats and oils are made from two kinds of molecules: glycerol (a type of alcohol with a hydroxyl group on each of its three carbons) and three fatty acids joined by dehydration synthesis. Since there are three fatty acids attached, these are known as triglycerides. The terms saturated, mono-unsaturated, and poly-unsaturated refer to the number of hydrogens attached to the hydrocarbon tails of the fatty acids as compared to the number of double bonds between carbon atoms in the tail. Fats, which are mostly from animal sources, have all single bonds between the carbons in their fatty acid tails, thus all the carbons are also bonded to the maximum number of hydrogens possible. Since the fatty acids in these triglycerides contain the maximum possible amount of hydrogen’s, these would be called saturated fats. The hydrocarbon chains in these fatty acids are, thus, fairly straight and can pack closely together, making these fats solid at room temperature. Oils, mostly from plant sources, have some double bonds between some of the carbons in the hydrocarbon tail, causing bends or “kinks” in the shape of the molecules. Because some of the carbons share double bonds, they’re not bonded to as many hydrogen’s as they could if they weren’t double bonded to each other. Therefore these oils are called unsaturated fats. Because of the kinks in the hydrocarbon tails, unsaturated fats can’t pack as closely together, making them liquid at room temperature. Many people have heard that the unsaturated fats are “healthier” than the saturated ones. Hydrogenated vegetable oil (as in shortening and commercial peanut butters where a solid consistency is sought) started out as…