Fatty acids not only provide energy but are also important structural components of lipids. Chemically, they are organic acids (carboxylic acids) with long hydrocarbon chains (A). Usually, the carboxyl group is esterified with alcohols like glycerol, sphingosine, or cholesterol. Free, nonesterified fatty acids (free fatty acids, FFA) are dissociated at physiological pHs. Fatty acids may contain double bonds (i. e., unsaturated fatty acids) that occur in cis-configuration under physiological conditions. If they contain only one double bond, they are called mono-unsaturated fatty acids (MUFA). Double bonds put a "kink" into the otherwise straight molecular chain, making the molecule more flexible. They also lower the melting point of a molecule, rendering the lipid more liquid. Technologically, the opposite path is used: hydrogenation of double bonds leads to firmer products, which are contained in many industrially produced foods as "hydrogenated (or hardened) fats." Hydrogenation, as well as other intensive heat treatments, can cause changes in the configuration of double bonds, leading to trans-configurations. Their potential negative health effects are under discussion—whatever the final outcome, they are definitely undesirable.
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