Kharkiv National Medical University Department of Medical and B ioorganic chemistry

1. KharkivNational Medical University Department of Medical and Bioorganic chemistry «Biological and Bioorganic Chemistry» Lecture№ 2 CLASSIFICATION, STRUCTURE AND CHEMICAL PROPERTIES OF CARBOHYDRATES Lecturer: As. Professor, Department of Medical and Bioorganic Chemistry,, Ph.D. LukianovaL.V.

2. Carbohydrates are in composition of cells and tissues of all plant and animal organisms. They compose basic part of organic substance on the Earth.

3. Functions of carbohydrates 1. Carbohydrates act as a major chemical repository for solar energy. x CO2 + y H2O + solar energy → Cx(H2O)y + x O2 carbohydrate Energy is released and used for life activities : Cx(H2O)y + x O2 → x CO2 + y H2O + energy 2. Carbohydrates form structural material for cells in plants, bacteria, fungi and insects. 3. Carbohydrates act as structural elements of vitally important compounds (nucleic acids, coenzymes, vitamins).

4. Carbohydrate: a polyhydroxyaldehyde or polyhydroxyketone, or a substance that gives these compounds on hydrolysis

6. Aldoses n = 1-8 Ketoses n = 1-7 Monosaccharide • - a carbohydrate that cannot be hydrolyzed to a simpler carbohydrate; • have the general formula CnH2nOn, where n varies from 3 to8. • aldose: a monosaccharide containing an aldehyde group • ketose: a monosaccharide containing a ketone group

7. Chiral center D- and L- Designations Sugars show optical isomerism.

8. Fischer Projections • Fischer projection:a two dimensional representation for showing the configuration of tetrahedral stereocenters: • horizontal lines represent bonds projecting forward; • vertical lines represent bonds projecting to the rear

9. D,L Monosaccharides According to the conventions proposed byFischer: • D-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the -OH on its penultimate carbon on the right • L-monosaccharide: a monosaccharide that, when written as a Fischer projection, has the -OH on its penultimate carbon on the left These two compounds serve as configurational standards for all monosaccharides!

10. D-glucose D-galactose D-mannose D-glucose L-glucose enantiomers diastereomers If there are n chiral centers in a molecule, it will have Noptical isomers N = 2n. Therefore, glucose has 24 =16 optical isomers.

11. Physical Properties • Monosaccharides are colorless crystalline solids, very soluble in water, but only slightly soluble in ethanol. • sweetness relative to sucrose:

12. Cyclic Structure • Monosaccharides have hydroxyl and carbonyl groups in the same molecule and exist almost entirely as five- and six-membered cyclic hemiacetals: • anomeric carbon: the new stereocenter resulting from cyclic hemiacetalformation; • anomers:carbohydrates that differ in configuration at their anomericcarbons.

13. Haworth Projections • five- and six-membered hemiacetals are represented as planar pentagons or hexagons, as the case may be, viewed through the edge; • most commonly written with the anomeric carbon on the right and the hemiacetal oxygen to the back right; • the designation –means that –OH on the anomeric carbon is cis to the terminal –CH2OH; – means that it is trans.

14. Haworth Projections

15. anomeric carbon atom Glycosidic OH-group anomers α-D-glucose D-glucose β-D-glucose Cyclic structure of glucoseAnomers

16. β–glucose α-glucose hemiacetal (glycosidic) hydroxyl α-D-glucopyranose Haworth projection formula α-D-glucose Fischer projection formula The structures of α-D-glucose and β-D-glucose may be drawn in a simple six membered ring form called pyranose structures. Pyran

17. α-D-ribofuranose β-D-ribofuranose Cyclic structure of ribose Furan

18. Conformational Formulas • for pyranoses, the six-membered ring is more accurately represented as a strain-free chair conformation

19. Conformational Formulas • if you compare the orientations of groups on carbons 1-5 in the Haworth and chair projections of -D-glucopyranose, you will see that in each case they are up-down-up-down-up respectively

20. Mutarotation • Mutarotation: the change in specific rotation that occurs when an -or -form of a carbohydrate is converted to an equilibrium mixture of the two:

21. place of cycle opening α-D-glucofuranose α-D-glucopyranose (36 %) D-glucose (open-chain form) 0.02 % β-D-glucopyranose (64 %) β-D-glucofuranose Ring-chain tautomerism

22. α-D-fructopyranose α-D-fructofuranose D-fructose β-D-fructofuranose β-D-fructopyranose Fructose

23. H+ D-glucopyranose 2,3,4,6,-tetra-O-methyl- D-glucopyranose Methyl-2,3,4,6,-tetra-O-methyl- D-glucopyranoside D-glucopyranose Chemical properties 1. Glycosides formation Methyl-D-glucopyranoside (mixture of α- and β –anomers) 2. Ethers formation

24. Glucose-1-phosphate 3. Esters formation.

25. glucitol glucose 4. Reduction mannitol mannose

26. 5. Oxidation a) Oxidation in alkaline medium (qualitative tests for aldoses and ketoses) • among the mild oxidizing agents used for this purpose is Tollens’ solution; • if the test is done properly, silver metal precipitates as a silver mirror: mixture of products (complex) Fehling solution(blue) red-brown ppt Carbohydrates which give these reactions are called reducing.

27. Glucose Gluconic acid Glucose Glucaric acid b) Oxidation in neutral medium with mild oxidizing agents gives aldonicacids. c) Oxidation in acidic medium with strong oxidizing agents gives saccharic acids.

28. Acidity of polyhydric alcohols is higher than that of monohydric ones, due to negative inductive effect (-I) of hydroxyl groups. Hydrogen atoms of polyhydric alcohols are easily replaced by some heavy metals with formation of chelates: Chelates have bright coloration and their formation is used for the qualitative determination of polyhydric alcohols

29. D-mannose D-glucose Enediol D-fructose 6. Interconversions of aldoses and ketoses in weak alkaline medium

30. Ascorbic Acid (Vitamin C) L-Ascorbic acid (vitamin C) is synthesized both biochemically and industrially from D-glucose:

31. Ascorbic Acid (Vitamin C) L-Ascorbic acid is very easily oxidized to L-dehydroascorbic acid. Both are physiologically active and are found in most body fluids:

32. Disaccharides Disaccharides are the carbohydrates which on hydrolysis give two same or different monosaccharides. hemiacetal acetal The two monosaccharide units are linked to each other by a bond called glycosidic linkage. 1.due to the glycosidic OH-group of one monosaccharide unit and any alcoholic OH-group of the other one (this is a group of reducing sugars). 2.due to the glycosidic OH-groups of both monosaccharide units (this is a group of non-reducing sugars).

33. -H2O OH HO Maltose From malt, the juice of sprouted barley and other cereal grains. It is the principal disaccharide obtained by the hydrolysis of starch. α-D-glucopyranose + αorβ-D-glucopyranose bound by α(1→4) glycosidic linkage

34. Maltose belongs to reducing sugarsbecause of the presence of free glycosidic hydroxyl group:

35. HO H -H2O H OH Lactose Lactose occurs in the milk of all mammals. Lactose is reducing sugar. Table sugar, obtained from the juice of sugar cane and sugar beet β-D-galactopyranose + αorβ-D-glucopyranose bound by β(1→4) glycosidic linkage

36. -1,2-гликозидная связь Sucrose Іs the most common disaccharide and is present in the sugar cane, sugar beet, plants juice and fruits. α-D-glucopyranose + β-D-fructofuranose bound by (1→2) glycosidic linkage Sucrose is non-reducing sugar

37. Polysaccharides are polymeric compounds in which a large number of monosaccharide units are joined by glycosidic linkages.

38. Starch (С6Н10О5)n amylose (20%) amylopectin (80%) Starch is used for energy storage in plants. Monomer unit is α-D-glucose (pyranose ring). It can be separated into two fractions: amylose and amylopectin; each on complete hydrolysis gives only D-glucose.

39. Amylose is a water soluble fraction. Аmylose is composed of continuous, unbranched chains of up to 4000 D-glucose units joined by-1,4-glycoside bonds. Mr = 160 000. α(1→4)

40. α(1→4) α(1→6) glycosidic linkage Amylopectin is water insoluble fraction. Amylopectin is a highly branched polymer of D-glucose. Chains consist of 24-30 units of D-glucose joined by -1,4-glycoside bonds and branches created by -1,6-glycoside bonds. Mr = 1-6 mln.

41. Cellulose is major structural polysaccharide in plants. It is probably the most abundant organic substance found in nature. Over 50% of the total organic matter in the living world is cellulose. Monomer unit – β-D-glucose (pyranose ring). Molecule is unbranched. It contains about 2500-12000 glucose units. Cellulose is a linear polymer of D-glucose units joined by -1,4-glycoside bonds. It has an average molecular weight of 400,000 g/mol, corresponding to approximately 2800 D-glucose units per molecule both rayon and acetate rayon are made from chemically modified cellulose β-(1→4)

42. Glycogen(С6Н10О5)n is the reserve carbohydrate for animals • like amylopectin, glycogen is a nonlinear polymer of D-glucose units joined by -1,4- and -1,6-glycoside bonds bonds • the total amount of glycogen in the body of a well-nourished adult is about 350 g (about 3/4 of a pound) divided almost equally between liver and muscle

43. Acidic Polysaccharides • Hyaluronic acid: an acidic polysaccharide present in connective tissue, such as synovial fluid and vitreous humor

44. Acidic Polysaccharides • Heparin • its best understood function is as an anticoagulant