The bulk of all cells is water, in which relatively small amounts of inorganic ions and several organic compounds are dissolved. The number of distinct organic chemical species in a cell is large, but most may be classified as carbohydrates, lipids, proteins, nucleic acids, or derivatives thereof. Those few compounds not so classified account for only a small fraction of the mass of the cell and are metabolically derived from substances in one of the four major classes. The four major classes of organic compounds have markedly different structures, properties, and biological functions, but each class contains two types of compounds: monomeric species with molecular weights of about 102 to 103 and polymeric biomolecules (biomacromolecules), with molecular weights of about 103 to 1010. The Web site of International Union of
Biochemistry and Molecular Biology (http://www.chem.qmw.ac.uk/iubmb/) is an excellent starting point for the classification and nomenclature of biochemical compounds.
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WHAT IT IS A three-phase plan that has been likened to the low-carbohydrate Atkins program because during the first two weeks, South Beach eliminates most carbs, including bread, pasta, potatoes, fruit and most dairy products. In PHASE 2, healthy carbs, including most fruits, whole grains and dairy products are gradually reintroduced, but processed carbs such as bagels, cookies, cornflakes, regular pasta and rice cakes remain on the list of foods to avoid or eat rarely.