Karen A. Beitler
Lipids are a group of polymers that have one major characteristic in common, they are hydrophobic or don't mix with water
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. Fats, steroids, triglycerides, fatty acids, phospholipids and waxes are important groups of lipids. Lipids store energy in their bonds and therefore animals store fat as an energy source.
Each molecule of fat is made up from two kinds of smaller molecules; glycerol and fatty acids. Glycerol is an alcohol; three carbons molecules with hydroxyl (-OH) groups attached to each. Glycerol absorbs water from the air is used as a sweetener, and in the manufacturing of cosmetics, liquid soap, liqueurs, ink, lubricants and dynamite. Fatty acids are long unbranched chains of hydrocarbons (H-C-H) with a carboxyl group (-COOH) at one end
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. When a glycerol's hydroxyl group reacts with the carboxyl group of a fatty acid a condensation reaction occurs and a water molecule is removed to form a monoglyceride. A second reaction yields a diglyceride and a third a triglyceride. Triglyceride (triglycerol) is therefore three fatty acids linked to a glycerol.
Saturated fatty acids have the maximum number of hydrogen atoms and are typically solid at room temperature. Unsaturated fatty acids have one or more carbon atoms with a double bond; this produces a bend in the molecules and they are liquid at room temperature. Fats that are liquid at room temperature are oils. There are an abundance of fatty acids that can all serve as one of the three chains in a fat molecule. All three can be saturated, unsaturated or any combination of both; this is what gives fats different physical and/or chemical properties. In general, shorter chains and less saturated fatty acids create softer, homogeneous fats
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. An example of a fatty acid that is polyunsaturated is linoleic acid (a main component in flax, sunflower and safflower oil). Oleic acid (in olive oil, grapeseed oil, acai) is monounsaturated and stearic acid (in animal fat and cocoa) is a saturated fatty acid.