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Unformatted text preview: Ch. 16 Carbohydrates Biomolecules Molecules that are used by living organisms in the processes responsible for life. There are four major classes 1) carbohydrates, 2) proteins, 3) nucleic acids, and 4) lipids. Carbohydrates The name means watered carbon, as the general formula is C n H 2n O n . When heated, they decompose into tar and H 2 O. They are actually aldehyde or ketone compounds with multiple hydroxyl groups. They compose most of the organic matter known. Four major roles of carbohydrates in living organisms: 1) They serve as energy stores, fuels, metabolic intermediates. 2) They form part of the structural framework of RNA and DNA. 3) They serve as structural elements in the cell walls of bacteria and plants. Cellulose is one of the most organic compounds on earth. 4) They are linked to many proteins and lipids. Also, carbohydrate units play key roles in cell-cell recognition processes. Monosaccharides - Structure Carbohydrates vary enormously in size, but they can be reduced to smaller units, or building blocks, called monosaccharides. When 2 monosaccharides are linked together, a di saccharide; when 3-10 are linked, an oligo saccharide; when more than 10 are linked, a poly saccharide. Monosaccharides are aldehydes or ketones with 2 or more hydroxyl groups, so there is extensive intermolecular H-bonds. This gives them relatively high melting and boiling points (often they char before they melt). They also readily H-bond with water molecules, so they are fairly soluble in water (100 grams of glucose in 100 mL H 2 O at 25C)....
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