Fats
All fats are derivatives of glycerol, combined with fatty acids. Glycerol is a simple alcohol (polyol) compound, comprising 3 hydroxyl groups. A hydroxyl is a functional group comprising an oxygen atom covalently bonded to a single hydrogen atom. Fatty acids comprise a carboxylic acid with a long aliphatic tail (chain). An aliphatic compound is a group of hydrocarbons that do not link together to form a ring.
Triglycerides – the common form of fat in animals – have 3 fatty acids. Humans store unused energy (calories) in triglycerides. Overeating high-carbohydrate foods packs on saturated triglycerides.
Chemical composition complexities aside, the biologically relevant facts of fats are that they act as an energy store, and that fats come in 2 forms: saturated and unsaturated.
A saturated fat has only single bonds between carbon atoms. The term saturated is used because the fat is chock full of hydrogen atoms.
In contrast, unsaturated fat has at least 1 double bond within the fatty acid chain. A fat molecule with only 1 double bond is monounsaturated. Molecules of fat with more than 1 double bond are polyunsaturated.
Hydrogen atoms are eliminated where double bonds are formed. Thus, metabolically, unsaturated fats hold a bit less energy (i.e., fewer calories) than an equivalent portion of saturated fat.
Unsaturated fats are regarded as healthier for human consumption; the more unsaturated, the better. Unsaturated fats metabolize more cleanly.
Nature equipped biological systems to recognize the shapes and other characteristics of molecules and process them accordingly. Metabolically, a saturated fat is treated to a different set of biochemical reactions than an unsaturated fat.
Each form of fat has a different shape. Fats are metabolized by geometry.
The more double bonds there are, the more readily a fat will react with oxygen. The tendency to rancidity is greater the more unsaturated the fat is. So, to preserve shelf life, fatty foods are commercially processed by hydrogenation: saturating the fat at high temperature, thus breaking the double bonds and slimming them to single bonds, with hydrogen attached.
