The Major Compounds of the Body

• Carbohydrates, commonly known as sugars, can be classified by a number of criteria:
• Type of carbonyl group (aldo or keto sugars)
• Number of carbons (pentoses [5 carbons], hexoses [6 carbons])
• Positions of hydroxyl groups on asymmetrical carbon atoms (d or l configuration, stereoisomers, epimers)
• Substituents (amino sugars)
• Number of monosaccharides joined through glycosidic bonds (disaccharides, oligosaccharides, polysaccharides)
• Lipids are structurally diverse compounds that are not very soluble in water (i.e., they are hydrophobic).
• The major lipids are fatty acids.
• Triacylglycerols (triglycerides) consist of three fatty acids esterified to the carbohydrate glycerol.
• Phosphoacylglycerols (phosphoglycerides or phospholipids) are similar to triacylglycerol but contain a phosphate in place of a fatty acid.
• Sphingolipids are built upon sphingosine.
• Cholesterol is a component of membranes and a precursor for molecules which contain the steroid nucleus, such as bile salts and steroid hormones.
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• Nitrogen is found in a variety of compounds in addition to amino sugars.
• Amino acids and heterocyclic rings contain nitrogens, which carry a positive charge at neutral pH.
• Amino acids contain a carboxyl group, an amino group, and a side chain attached to a central carbon.
• Proteins consist of a linear chain of amino acids.
• Purines, pyrimidines, and pyridines have heterocyclic nitrogen-containing ring structures.
• Nucleosides consist of a heterocyclic ring attached to a sugar.
• A nucleoside plus phosphate is a nucleotide.
• Glycoproteins and proteoglycans have sugars attached to protein components.