Carbohydrate chemistry ppt lecture 2 BIOCHEMISTRY
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Carbohydrate chemistry ppt lecture 2 BIOCHEMISTRY

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Structure and Isomerism of carbohydrates

Structure and Isomerism of carbohydrates

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  • SUCROSE(+66.5) ON HYDROLYSIS GLUCOSE (+52.5) FRUCTOSE (-92)DEXTRO – LEVOINVERT SUGAR

Carbohydrate chemistry ppt lecture 2 BIOCHEMISTRY Carbohydrate chemistry ppt lecture 2 BIOCHEMISTRY Presentation Transcript

  • Carbohydrate chemistry II Structure and Isomerism Dr. Vijay Marakala, MD. Assistant professor BIOCHEMISTRY SIMS & RC
  • Structure of monosaccharide Fisher projection • The straight chain structural formula Haworth projection • Cyclic formula or ring structure X-ray diffraction analysis • Boat and chair form
  • Straight chain Ring structure Chair form
  • Isomerism • The compounds possessing identical molecular formula but different structures are called isomers. Various types of isomerism 1. Structural isomerism 2. Stereoisomerism
  • Structural isomerism • Same molecular formulae but differ from each other by having different structures.
  • Stereoisomerism • Same molecular formula and same structure but they differ in configuration. • That is arrangement of their atoms in space. • Presence of asymmetric carbon atoms allow the formation of stereoisomerism
  • Stereoisomerism • The important types of stereoisomerism associated with glucose are D and L isomerism Optical isomerism Epimerism α and βanomerism
  • D and L isomerism
  • Optical isomerism • Optical activity is the capacity of a substance to rotate the plane polarized light passing through it. Clockwise direction • Dextrorotatory(d) or (+) Counterclockwise direction • Levorotatory(l)or (-)
  • Optical isomerism
  • Epimerism • Epimerism is the stereoisomerism if two monosaccharides differ from each other in their configuration around a single specific carbon(other than anomeric) atom.
  • Epimerism
  • Anomerism • These are isomers obtained from the change of position of hydroxyl group attached to the anomeric carbon e.g. and glucose are 2 anomers. • Also and fructose are 2 anomers.
  • Anomerism
  • • Mutarotaion is defined as the change in the specific optical rotation by the interconversion of α and β forms of D glucose to an equilibrium mixture Mutarotaion
  • Structure of oligosaccharides • Disaccharides Disaccharides Reducing Maltose Lactose Isomaltose Nonreducing Sucrose
  • DISACCHARIDES • These are glycosides formed by the condensation of 2 simple sugars. • If the glycosidic linkage involves the carbonyl groups of both sugars ( ) the resulting disaccharide is • On the other hand, if the glycosidic linkage involves the carbonyl group of only one of the 2 sugars (as in maltose and lactose) the resulting disaccharide is reducing.
  • POLYSACCHARIDES • These are formed by the condensation of n molecules of monosaccharides with the removal of n-1 molecules of water. Since condensation involves the carbonyl groups of the sugars, leaving only one free carbonyl group at the end of a big molecule, polysaccharides are non-reducing. • They are of 2 types: 1. Homopolysaccharides (e.g. Starch, Glycogen, cellulose). 2. Heteropolysaccharides (e.g. glycosaminoglycans, glycoproteins)
  • - 1,4 linkage between two glucose units -1,6 linkage between two glucose units
  • Aldehyde group H-C=O Monosaccharides Enantiomers Mirror images of each other Disaccharides sucrose = glucose + fructose Lactose = galactose + glucose Maltose = glucose + glucose Oligosaccharides Polysaccharides Homo- Starch, glycogen, cellulose Hetero- GAGs Epimers Differ in configuration around one specific carbon atom Isomers Same chemical formula Ketoses Keto group C=O Aldoses