1. Lecturer: PROFESSOR F.E. EJEZIE Ph.D

2. Course Title: BIC 202 Chem of Biol Mols & Biochem Catalysis

3. Topic: Chem of Carbohydrates

4. Course Outline Introduction Definition & functions of CHO’s Classification of CHO’s Derivatives of Monosacharides Stereochemistry of Monosacharides Complex Carbohydrates Reducing and non-reducing sugars Common chem rxns of some CHO’s

5. Introduction Definition: Biochemistry is the study of the chem processes in living organisms. Living organisms include: animals/man, plants and microorganisms. BCH deals with the structures, reactions/enzymes and functions of cell components – CHO’s, lipids, proteins, nucleic acids (DNA & RNA) and other biomolecules.

6. Medical Biochemistry Is concerned with how to make life better for man (good health) and disease conditions.

7. Carbohydrates Definition(structurally): As polyhydroxy aldehydes, ketones and their derivatives. Complex CHO’s may also contain such other elements as N, S and P, in addition to C, H & O. They are the most abundant class of organic compounds found in living organisms. They originate as products of photosynthesis – an endothermic reductive condensation of CO2, H2O, requiring light energy and the pigment chlorophyll.

8. Functions of CHO’s Major source of energy for plants and animals (eg starch & glycogen) Structural material (eg cellulose in plants and chitin in arthropods). Ribose (a 5-carbon monosaccharide) is an important component of coenzymes (FAD & NAD) and genetic material (RNA). The related deoxyribose is a component of DNA.

9. Functions of CHO’s contd Involved in biological recognition processes on cell surfaces (cell communication) Play key roles in immune system, blood clotting, fertilization and development. Provide precursors in several biosynthetic rxns. Source of fibre in diet.

10. Classification of CHO’s Based on number of sugars: i)Monosaccharides, ii)Disaccharides, iii) Oligosaccharide iv) Polysacchrides Based of functions: i) Storage CHO’s eg starch and glycogen ii)Structural CHO’s eg cellulose and chitin.

11. General Chem Features of CHO’s They have at least 1 and often 2 or more asymmetric carbon centres They exist either in linear or ring forms They form polymeric structures via glycosidic bonds They have the potential to form multiple hydrogen bonds with water and other molecules in their environment. These features are responsible for the many functions of CHO’s.

12. The Monosaccharides (simple sugars) They cannot be hydrolysed into simpler forms under mild conditions. Generally contain 3-7 carbon atoms May be classified as: i) Aldoses with aldehyde functional grps (-CHO) or Ketoses with keto grps (-C=O). Simplest aldose is glyceraldehyde Simplest ketose is dihroxyacetone

13. The Monosaccharides contd May be classified based on no of carbon atoms i)The trioses – contain 3 carbon atoms eg’s glyceraldehyde, dihydroxyacetone ii) The tetroses – contain 4 carbon atoms eg’s erythrose, threose, erythrulose iii) The Pentoses- contain 5 carbon atoms eg’s Arabinose, Ribose, Ribulose, Xylose, Xylulose, Lyxose. iv) The Hexoses –contain 6 carbon atoms eg’s Fructose, Galactose, Glucose, Mannose, Sorbose. v) The Heptoses – contain 7 carbon atoms eg’s Sedoheptulose, Mannoheptulose. (look up the structures, classify as aldoses and ketoses)

14. The Disaccharides On hydrolysis yield 2 simple sugars: eg’s i)Maltose (Glu + Glu) ii)Isomaltose (Glu + Glu) iii)Lactose (Glu + Gal) iv)Sucrose (Glu + Fru) v)Cellulose (Glu + Glu) vi)Gentiobiose (Glu + Glu) vii)Trehalose (Glu + Glu) viii) Melibiose (Glu + Gal)

15. The Trisaccharides On hydrolysis yield 3 simple sugars: eg’s i)Maltotriose (Glu + Glu + Glu) ii)Raffinose (Gal + Glu + Fru) – not digested/absorbed in human GIT due to lack of appropriate enzymes. (look up the structures and note the bonds linking them up)

16. The Tetrasaccharides On hydrolysis yield 4 simple sugars: eg Stachyose (Gal + Gal +Glu + Fru) – not digested/absorbed in human GIT due to lack of appropriate enzymes. (look up the structures and note the bonds linking them up)

17. The Oligosaccharides Contain 3- 10 simple sugars They mainly form components of complex CHO’s – eg glycoproteins. Some antibiotics are oligosaccharides or contain oligosaccharide groups eg streptomycin, aburamycin C, sulfurmycin B, Bleomycin A2.

18. Thank you.