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Carbohydrates Carbohydrates (CHO): are aldehyde or ketone group with multiple hydroxyl groups having an empirical formula of (CH2O)n . General biological role: CHO make up most of plants tissues at a less extent, the animal tissues. As energy stores: starch in plants and glycogen in animals are major polysaccharides that are mobilized to give glucose which is the prime fuel for generation of energy. ATP is a phosphorylated sugar derivatives and universal for free energy. Ribose and de oxy ribose sugars form part of the structural framework of DNA and RNA, these sugars rings have conformation flexibility which is important in the storage and expression of the genetic information. Polysaccharides are structural element in the cell wall of bacteria and plants. cellulose is the main component of plants cell wall. Classification 1- Monosaccharide: a single sugar unit having a carbonyl group (either aldehyde at C1 or keton at C2) . D- glyceraldehyde Di hydroxyl acetone (DHA) Aldose Ketose 1 4C sugar = tetrose (either aldose or ketose) 5C sugar= pentose = 6C sugar= hexose = 7C sugar= heptose = Properties of monosaccharide: 1- White, solids, soluble in water, insoluble in non polar solvents. 2- All monosaccharide (having free aldehyde or keton group) . 3- All monosaccharide (except DHA) have one or more a symmetric carbon atom (atom bound to 4 different groups) ( carbon atom having double or triple bonds excluded from this category). To determine whether the isomer is D or L we must look for the orientation of (OH) group of the carbon atom farther from the carbonyl group and near the CH2OH group, if to the right the isomer is D, if to the left the isomer is L. Since all monosaccharide (except DHA) have one or more a symmetric carbon. They are optically active and tend to rotate the plane of polarized light either to the right (d or +) called dextrorotatory or to the left ( l or —) called levorotatory. 2 Note: it is important note that there is no relation between D and d or L and l. a sugar may have D form but rotates the plane of polarized light to the right or left. Ex: D (+) glucose or D (—) glucose 3 Sugar derivatives and biological importance: Glycosides: compounds formed by the condensation of a monosaccharide with the (OH) group of another monosaccharide (forming disaccharides) or with the (OH) group of a non monosaccharide unit and this is called a glycan portion. Ex: 1-Vanillin D- glucoside (glucovanillin or vallinoside): sourse of vanilla flavor 2- Digoxin and Digitoxin Stimulator for cardiac muscle contraction Digoxin Digitoxin Onset 15-30 min longer acting Half life 32-40 hr. half life 4-6 days (preferred to use). Deoxy and amino sugars Deoxy sugars are sugar in which (OH) group has been replaced by hydrogen CHOH—— CH2 and CH2OH——CH3 4 Ex: - Amino sugars: have —NH2 group replacing (OH) group (usually at C2). Ex: D-glucosamine (chitosamine) A constituent of mucopolysaccharides and mucoproteins such as hyaluronic acid, heparin and blood group substances , (heparin): is antithrombic agent. 5 galactos amine (chondrosamine) A constituent of chondroitin (found in cornea, cartilage, skin, adult bones, tendons, and heart valve). Several antibiotics (erythromycin and carbomycin) contain amino sugars. Erythromycin contain a di methyl amino sugar. Carbomycin contain 3- amino D- ribose. Streptomycin is another amino sugar antibiotic. Ascorbic acid (Vit. C) is a sugar acid, a very stable compound and undergoes oxidation to dehydroascorbic acid. Prolonged lack of Vit. C causes scurvy and decreased resistance to disease. 6 Sugar phosphate: key intermediate in the process of glycolysis (break down of glucose to give CO2, H2O, and energy ATP). 7