بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم

2. Introduction to Carbohydrates

3. Carbohydrates are the most abundant organic molecules in nature. • Have a wide range of functions, including : • Provide energyin the diet of most organisms, • act as a storage form of energy in the body, • serve as cell membranecomponents that mediate some forms of intercellular communication. • also serve as a structuralcomponentof many organisms, including cell walls of bacteria, exoskeleton of many insects, and fibrous cellulose of plants.

4. The empiric formula for many of the simpler carbohydrates is (CH2O)n,  hencethe name “hydrate of carbon.” (CH2O)n

5. Classification and Structure of Carbohydrates • Monosaccharides(simple sugars) which can be classified according to the number of carbon atoms they contain. • Disaccharides contain 2 monosaccharide units, • oligosaccharides2 - 10 monosaccharide units, • Polysaccharides> 10 monosaccharide units up to Hundreds

6. Carbohydrates with an aldehydeas their most oxidized functional group are called aldoses, whereas those with a keto group as their most oxidized functional group are called ketoses. • For example, glyceraldehyde is an aldose, whereas dihydroxyacetone is a ketose.

7. CLASSIFICATION OF MONOSACCHARIDES: Can be carried out by one of two methods: • According to the number of carbon atoms: Trioses, tetroses, pentoses, hexoses, heptoses, octoses. • According to the characteristic carbonyl group (aldehyde or ketone group): - Aldo sugars: aldoses: monosaccharides containing aldehyde group e.g. glucose, ribose, erythrose and glyceraldehyde. - Keto sugars: ketoses: monosaccharides containing ketone group e.g. fructose, ribulose and dihydroxy acetone.

8. Examples of monosaccharides found in humans, classified according to the number of carbons they contain.

9. carbonyl group

10. ASYMMETRIC CARBON ATOM: • It is a carbon atom attached to four different atoms or groups of atom • Any compound having asymmetric carbon(s) possess the following properties: • 1. Formation of isomers. • 2. Shows optical activity

11. The monosaccharides with asymmetric carbon atoms are optically active (all except dihydroxyacetone).

12. Isomers • are compoundswhich: • have the same molecular weight, same percentage composition, and • differ in their physical and chemical properties. • Stereoisomers: are compounds that have the same structural formula but differ in spatial configuration (arrangement of atoms and groups of atoms in space around the asymmetric carbon(s) i.e. different configuration). • The number of possible stereoisomers of any given compound is 2n, where n is the number of asymmetric carbon atoms.

13. Enantiomers(= D & L isomers ) • (e.g. D & L Glucose) • They are pairs of compounds that have the same structural formulas but • differ in spatial configuration; • one of them is the mirror image of the other and • they rotate the plane of polarised light equally but in opposite directions.

14. Cyclization of monosaccharides (α and β anomers) • Most Monosaccharidesof five or more carbon atoms are present in cyclic or ring forms. • in which the aldehyde (or ketone) group has reacted with an alcohol group on the same sugar, making the carbonyl carbon (carbon 1 for an aldose or carbon 2 for a ketose)  asymmetric. The anomeric Carbon is asymmetric carbon atom obtained from the carbonyl carbon atom in the ring forms of monosaccharides α- and β - anomers are isomers of monosaccharides that differ from each other only in configuration about the anomeric carbon.

17. anomericCarbon leads to: • The cyclic α and β anomers of a sugar in solution are in equilibrium with each other, and can be spontaneously interconverted (a process called mutarotation. • Reducing sugars: If the oxygen on the anomeric carbon of a sugar is not attached to any other structure, that sugar can act as a reducing agent and is termed a reducing sugar.

18. Haworth Configuration of Cyclic Sugars: • It is the ring configuration with characteristic orientation of attached groups to carbon backbone as follows: all groups to the right of carbon are oriented down while all groups to the left of carbons are oriented up Except those around carbon # 5, the reverse orientation occurs.

20. Epimers: • Are 2 monosaccharidesdiffer only in the configuration around one specific carbon atom (not the anomeric carbon or the prelastsubterminal carbon).

21. Joining of monosaccharides • Monosaccharides can be linked (to each other or to non-carbohydrate materials) by glycosidic bonds to create larger structures  N- and O-glycosides

23. Monosaccharides can be joined together to form disaccharides, oligosaccharides, and polysaccharides. Important disaccharides include • lactose (galactose + glucose), • sucrose (glucose + fructose), and • maltose (glucose + glucose). • Important polysaccharides include • Branched:  glycogen (from animal sources) &   starch (plant sources) • Unbranched: cellulose (plant sources); • each is a polymer of glucose.

25. Thank You