polyunsaturated fat

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fat

 [fat]
1. the adipose tissue of the body.
2. a triglyceride (or triacylglycerol) that is an ester of fatty acids and glycerol. Each fat molecule contains one glycerol residue connected by ester linkages to three fatty acid residues, which may be the same or different. The fatty acids may have no double bonds in the carbon chain (saturated fatty acids), one double bond (monounsaturated), or two or more double bonds (polyunsaturated). Essential fatty acids cannot be synthesized by the body but must be obtained from the diet or from intravenous infusion of lipids.
Saturated and Unsaturated Fats. All of the common unsaturated fatty acids are liquid (oils) at room temperature. Through the process of hydrogenation, hydrogen can be incorporated into certain unsaturated fatty acids so that they are converted into solid fats for cooking purposes. Margarine is an example of the hydrogenation of unsaturated fatty acids into a solid substance.
brown fat a thermogenic type of adipose tissue containing a dark pigment, and arising during embryonic life in certain specific areas in many mammals, including humans (see illustration); it is prominent in the newborn. Called also brown adipose tissue.
Sites of brown fat in the neonate. From McKinney et al., 2000.
neutral fat fat (def. 2).
polyunsaturated fat a fat containing polyunsaturated fatty acids; see also fat.
saturated fat a fat containing saturated fatty acids; see also fat.
unsaturated fat a fat containing unsaturated fatty acids; see also fat.

polyunsaturated fat

A saturated fatty acid (i.e., an alkyl-chain fatty acid) with two or more ethylenic carbon–carbon double bonds; because of the double bond, not every carbon is saturated with hydrogen atoms—i.e., there are fewer hydrogens—which reduces the strength of the compound's intermolecular forces, resulting in a significant lowering of the compound’s melting point.

Polyunsaturated fats in humans
• Linoleic PFAs—two double bonds between 9/10 (Δ9) and 12/13 (Δ12); e.g., CnH2n-COOH.
• Linolenic PFAs—three double bonds, Δ9, Δ12, Δ15; e.g., CnH2n-5-COOH.
• 4-doubled bond PFAs—four double bonds, Δ5, Δ8, Δ11, Δ14; e.g., arachidonic acid.

pol·y·un·sa·tu·ra·ted fat

(pol'ē-ŭn-sach'ŭr-ā-tĕd fat)
A type of unsaturated fat. Diets high in unsaturated fat produce lower cholesterol levels.