Carbohydrates comprise a heterogeneous group of compounds of various sizes that play important roles in the life of all organisms. These include:
■ Carbohydrates are a common food source from which organisms can obtain energy and make cellular material.
■ Two sugars form a part of the nucleic acids, DNA and RNA. ■ nucleic acids, p. 31
■ Certain carbohydrates serve as a reserve source of food in bacteria. ■ storage granules, p. 67
■ Sugars form a part of the bacterial cell wall.
The one feature common to all diverse carbohydrates is that they contain carbon, hydrogen, and oxygen atoms in an approximate ratio of 1:2:1. This is because they contain a large number of alcohol groups (—OH) in which the C is also bonded to an H atom to form H—C—OH. Polysaccharides are high molecular weight compounds and are linear or branched polymers of their subunits. Oligosaccharides are short chains. The term sugar is often applied to monosaccharides (mono means "one"), a single molecule, and disaccharides (di means "two"), which are two monosaccharides joined together by covalent bonds. Carbohydrates also usually have an aldehyde group
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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.