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2-Deoxy-D-ribose, an aldopentose

FIGURE 7-1 Representative monosaccharides. (a) Two trioses, an aldose and a ketose. The carbonyl group in each is shaded. (b) Two common hexoses. (c) The pentose components of nucleic acids. d-Ribose is a component of ribonucleic acid (RNA), and 2-deoxy-d-ribose is a component of deoxyribonucleic acid (DNA).

aldotetroses and ketotetroses, aldopentoses and ke-topentoses, and so on. The hexoses, which include the aldohexose d-glucose and the ketohexose d-fructose (Fig. 7-1b), are the most common monosaccharides in nature. The aldopentoses d-ribose and 2-deoxy-d-ribose (Fig. 7-1c) are components of nucleotides and nucleic acids (Chapter 8).

Monosaccharides Have Asymmetric Centers

All the monosaccharides except dihydroxyacetone contain one or more asymmetric (chiral) carbon atoms and thus occur in optically active isomeric forms (pp. 1719). The simplest aldose, glyceraldehyde, contains one chiral center (the middle carbon atom) and therefore has two different optical isomers, or enantiomers (Fig. 7-2).

Mirror

Mirror

CH2OH

Ball-and-stick models

CH2OH

Ball-and-stick models

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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