1. CARBOHYDRATES Dr. Vidya.D Asst. Professor, College of Pharmacy, Prince Sattam Bin Abdul Aziz University, Kingdom of Saudi Arabia PHL – 213 Biochemistry - I

2. Objectives Identify the functions of carbohydrates. Name the primary sources of carbohydrates. Describe the classification of carbohydrates.

3. Facts Primary source of energy for the body Least expensive and most abundant of the energy nutrients Named for the chemical elements they are composed of—carbon, hydrogen, and oxygen

4. Functions Provide energy Protein-sparing action Normal fat metabolism Provide fiber

5. Providing Energy  Each gram of carbohydrate provides 4 calories.  A body needs a constant energy supply.  A half day’s supply of carbohydrates is stored in the liver and muscles for use as needed.  Stored form is called glycogen.

6. Protein-Sparing Action The primary function of proteins is to build and repair tissues. When enough carbohydrates (at least 50–100 g/day) are ingested, proteins are spared to be used for their primary function.

7. Normal Fat Metabolism Without an adequate supply of carbohydrates, fat is not metabolized to meet energy requirements. Ketones are produced as a byproduct of fat metabolism. Ketosis may result.

8. Providing Fiber Dietary fiber is found in grains, vegetables, and fruits. Recommended intake is 20–35 g/day. Fiber lowers blood glucose levels; may prevent some colon cancers; and helps prevent constipation, hemorrhoids, and diverticular disease by softening stool.

9. Food Sources Principal sources of carbohydrates are plant foods:  e.g. Cereal grains, Vegetables, Fruits, Nuts, Sugars The only substantial animal source is milk.

11. Aldehyde group H-C=O Monosaccharides Enantiomers Mirror images of each other Disaccharides sucrose = glucose + fructose Lactose = galactose + glucose Maltose = glucose + glucose OligosaccharidesPolysaccharides 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 Simple (or ) small sugars Complex (or ) large sugars

12. Monosaccharides Sweet In taste Not hydrolysable Have three to seven carbons 3 carbons=Triose 4 carbons=Tetrose 5 carbons=Pentose 6 carbons=Hexose 7 carbons=Heptose

13. 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

14. Straight chain Ring structure Chair form

18. Isomerism The compounds possessing identical molecular formula but different structures are called isomers. Various types of isomerism 1. Structural isomerism 2. Stereoisomerism

19. Structural isomerism Same molecular formulae but differ from each other by having different structures.

20. 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

21. Stereoisomerism The important types of stereoisomerism associated with glucose are D and L isomerism Optical isomerism Epimerism α and βanomerism

22. D and L isomerism

23. 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 (-)

24. Optical isomerism

25. Epimerism Epimerism is the stereoisomerism if two monosaccharides differ from each other in their configuration around a single specific carbon(other than anomeric) atom.

26. Epimerism

27. 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.

28. Anomerism

29. 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

30. Types: 1. Aldoses 2. Ketoses Aldoses contain Aldehydic group –CHO Ketoses contain Ketonic group –CO-

32. Name of the sugar Role IN the bodyExample TrioseImportant in cellular respiration, in the glycolysis step. D-glyceraldehyde L- glyceraldehye Dihydroxyacetone PentosesThey form the backbone of polysaccharides, Proteins, Lipids & nucleic acids Ribose Ribulose HexosesGlucose - Primary energy molecule Fructose - energy molecule in semen Galactose - dairy products, sugar beets, gums and mucilage Mannose - it forms part of glycolipids & glycoproteins in several tissues. Glucose, Fructose Galactose, Mannose Talose, Allose, Idose

33. Derivatives of monosaccharides 1) Sugar phosphates Metabolized as phosphate esters 2) Deoxy sugars Hydrogen atoms replaces -OH group on C-2. Important to structure of nucleic acids. 3) Amino sugars Amino group (NH-) substituted for -OH group in monosaccharide. 4) Sugar alcohols Replace carbonyl oxygen to form polyhydroxy alcohols e.g. glycerol --> glyceraldehyde Replace “-ose” with “-itol”. Ribose --> ribitol 5) Sugar acids Oxidation of carbonyl carbon or highest carbon. glucose --> gluconate or glucuronate Important in many polysaccharides. 6) Ascorbic acid Derived from D-glucuronate. Primates cannot do the conversion, so must be supplied in the diet.

34. Glucose Polyhydroxy aldehyde Dextrose=Dextrorotatory Grape sugar Blood Sugar - 110mg/1000mL in blood Energy source for the body Combines with others to form disaccharides

35. Importance of Glucose Most widely used Hexose An energy source A precursor forms: Cellulose, Glycogen, Starch etc. Hypoglycemia and Hyperglycemia

36. Importance of Fructose Found in foods and Drinks 1 to 2 times sweeter than table sugar Used as artificial sweetener Anaerobic fermentation raw material for bacteria and yeasts. Apricots, apples, grapes etc.

37. Fructose in body(from Sucrose)

39. Structure of Oligosaccharides Disaccharides Reducing Maltose Lactose Isomaltose Non-reducing Sucrose

40. DISACCHARIDES

48. 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 (or) Homoglycans - composed of one type of monosaccharide(e.g. Starch, Glycogen, cellulose). 2. Heteropolysaccharides (or ) Heteroglycans – composed of more than one type of monosaccharide (e.g. glycosaminoglycans, glycoproteins)

49. POLYSACCHARIDES Often classified according to their biological role: 1) starch and glycogen - storage polysaccharides Both are homoglycans. Starch is storage form in plants and fungi. Glycogen is storage form in animals. Bacteria contain both.

50. Starch Starch - mixture of amylose and amylopectin amylose is an unbranched polymer of 100-1000 D-glucose in an a-(1 --> 4) glycosidic linkage. amylopectin is a branched polymer a-(1--> 6) branches of residues in an a-(1 --> 4) linkage; overall between 300-6000 glucose residues, with branches once every 25 residues; side chains are 15- 25 residues long α-amylase is an endoglycosidase found in human saliva but also plants that randomly hydrolyzes the a (1--> 4) bond of amylose and amylopectin. β-amylase is an exoglycosidase found in higher plants that hydrolyzes maltose residues from non-reducing ends of amylopectin.

53.  - 1,4 linkage between two glucose units  -1,6 linkage between two glucose units

54. Glycogen Glycogen - branched polymer of glucose residues with branches every 8-12 residues with branches containing as many as 50,000 glucose residues

55. Cellulose & Chitin - structural polysaccharides Cellulose - straight chain homoglycan of glucose with b- (1--> 4) linkages with alternating glucose molecules; ranges in size from 300-15,000 glucose residues Extensive H-bonding within and between cellulose chains. Makes bundles or fibrils ---> rigid. Chitin - linear polymer of N-acetylglucosamine residues Alternating 180o with b - (1 --> 4) linkage. Lots of H-bonding between adjacent strands.

57. Heteroglycans (or) Hetropolysaccharides (or) Glycoconjugates

58. Proteoglycans Complexes of polysaccharides called glycosaminoglycans & core proteins. Found in extracellular matrix of connective tissues. Glycosaminoglycans  are unbranched heteroglycans  made of disaccharide units (amino sugar, D- galactosamine or D-glucosamine & alduronic acid). e.g. hyaluronic acid Found in cartilage and synovial fluid. Proteoglycan cartilage

59. Peptidoglycans Found in cell wall of bacteria. Composed of alternating residues of N- acetylglucosamine and N-acetylmuramic acid joined by b- (1--> 4) linkages.

60. Glycoproteins Proteins with oligosaccharides attached. Carbohydrate chains are from 1-30 residues in length. Examples: enzymes, hormones, structural proteins, transport proteins. Found in eucaryotic cells. Can be attached to proteins with one of two configurations: O-linked - carbohydrate bonded to -OH of serine or threonine N-linked - carbohydrate (usually N-acetylglucosamine) linked to asparagines

61. ROLES OF CARBOHYDRATES IN BIOLOGY Carbohydrates serve as information-rich molecules that guide many biological processes. Examples include: 1) Asialoglycoprotein receptor Present in liver cells; binds to asialoglycoproteins to remove them from circulation Presence of sialoglycoprotein prevents glycoproteins such as antibodies and peptide hormones from being internalized Presence of sialic acid on terminal galactose on these proteins mark the passage of time; when they are removed (usually by the protein itself), the glycoproteins are removed from circulation.

62. 2) Lectins Carbohydrate-binding proteins of plant origin. Contain 2 or more binding sites for carbohydrate units -> cross-link or agglutinate erythrocytes and other cells. 3) Many viruses and bacteria can gain entry into host cells via carbohydrates displayed on cell surface. Influenza virus contains a hemagglutinin protein that recognizes sialic acid residues on cells lining respiratory tract. Neisseria gonorrhoeae infects human genital or oral epithelial cells because of recognition of cell surface carbohydrates; other cells lack these carbohydrates.

63. Contd.. 4) Interaction of sperm with ovulated eggs Ovulated eggs contain zona pellucida, an extracellular coat made of O- linked oligosaccharides. Sperm cells have receptor for these carbohydrates. Binding of sperm to egg causes release of proteases and hyaluronidase, which dissolve zona pellucida to allow sperm entry. 5) Selectins Carbohydrate-binding adhesion proteins that mediate binding of neutrophils and other leukocytes to sites of injury in the inflammatory response. 6) Homing receptor of lymphocytes Homing is phenomenon in which lymphocytes tend to migrate to lymphoid sites from which they were originally derived. Mediated by carbohydrates on lymphocyte surface and endothelial lining of lymph nodes.