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Lipids Structure types and Functions Part 1
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Lipids are a diverse group of hydrophobic molecules. Lipids are varied in form and function. • They include waxes and certain pigments, but we will focus on the types of lipids that are most biologically important: fats, phospholipids, and steroids. • A fat is constructed from two kinds of smaller molecules. glycerol and fatty acids . Glycerol is an alcohol each of its three carbons bears a hydroxyl group. A fatty acid has a long carbon skeleton, usually 16 or 18 carbon • atoms in length. • In making a fat, three fatty acid molecules are each joined to glycerol by an ester linkage, a bond formed by a dehydration reaction between a hydroxyl group and a carboxyl group. The resulting fat, also called a triacylglycerol, thus consists of three fatty acids linked to one glycerol molecule. • The terms saturated fats and unsaturated fats are commonly used in the context of nutrition. These terms refer to the structure of the hydrocarbon chains of the fatty acids. If there are no double bonds between carbon • atoms composing a chain, then as many hydrogen atoms as possible are bonded to the carbon skeleton. Such a structure is said to be saturated with hydrogen, and the resulting fatty acid is therefore called a saturated fatty acid . • An unsaturated fatty acid has one or more double bonds, with one fewer hydrogen atom on each double-bonded carbon. Nearly all double bonds in naturally occurring fatty acids are cis double bonds, which cause a kink in the hydrocarbon chain wherever they occur. • Phospholipids • Cells as we know them could not exist without another type of lipid—phospholipids. Phospholipids are essential for cells because they are major constituents of cell membranes. A phospholipid is similar to a fat molecule but has only two fatty acids attached to glycerol rather than three. The third hydroxyl group of glycerol is joined to a phosphate group, which has a negative electrical charge in the cell. • #LipidsComposition
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