Carbohydrate Chemistry Lecture Notes PDF

Carbohydrate Chemistry ILOs:  Enumerate biological importance of carbohydrates  Classify carbohydrates.  Identify configurations of monosaccharides.  Describe some members of disaccharides.  Recognize polysaccharides.  Discuss carbohydrates as conjugates. ...

Carbohydrate Chemistry ILOs:  Enumerate biological importance of carbohydrates  Classify carbohydrates.  Identify configurations of monosaccharides.  Describe some members of disaccharides.  Recognize polysaccharides.  Discuss carbohydrates as conjugates.  Carbohydrates  The most abundant form of organic matter on earth.  Contain the elements C, H, and O  Produced by the fundamental pathway of photosynthesis combining CO2 and H2O  All animals are ultimately reliant on this source of new organic material. Definition  Carbohydrates are poly hydroxyl aldelydes or ketone derivatives that are  found in plants in the form of starch and cellulose and in animal in the form of glycogen in liver and muscle  Biological importance of Carbohydrates  Carbohydrates are the major source of metabolic energy, both for plants and animals,used to form chitin in animal and cellulose in plants  Source of building blocks for other molecules: (e.g. conversion to fat, amino acids, nucleic acids)  Cell surface receptors (short chains linked to lipids and proteins),cell membrane,DNA,RNA and vitamins B2,C  Carbohydrates in the form of fibers can help to lower blood glucose and cholesterol levels and prevent constipation  Sources of Carbohydrates  Carbohydrates are found in bread, beans, milk, potatoes, soft drinks, and corn.  Classification of carbohydrates  Carbohydrates are classifications based on the number of sugar units in total chain into:  Monosaccharides: single sugar unit.  Disaccharides: two sugar units.  Oligosaccharides: 3 to 10 sugar units  Polysaccharides: more than 10 units Monosaccharides  Monosaccharides serve as the building units and simplest form of carbohydrates. Simple sugure  Classification of monosaccharides:  A) According to the presence of aldhyde or ketone group  1) Aldoses: it contains an aldehyde group  2) Ketoses: the sugars contain ketone group  B) According to the number of carbon atoms in the backbone:  C3: Triose. C4:Tetroses.  C5:Pentose. C6:Hexose.  C7:Heptose.  C) According to the number of carbon atoms and active group: Number of Aldoses Ketoses Carbons Trioses Glyceraldehyde Didroxyacetone Tetroses Erythrose Erythrulose Pentoses Ribose, Xylose Ribulose,Xylulose Hexoses Galactose, Glucose, Mannose Fructose Heptoses Heptose Sedoheptulose Examples of Monosaccharides: Biological importance of monosaccharides  Ribose is a component of ribonucleic acid (RNA).  Deoxyribose is a component of deoxyribonucleic acid (DNA)  Glucose is the sugar of blood.  Fructose is the sugar of semen.  Galactose is synthesized in mammary gland to make the lactose of milk (sugar of milk).  Mannose is a constituent of many glycoproteins. Sugars and other fermentable carbohydrates : Provide substarte for the action of oral bacteria ,which in turn lower salivary PH the resultant action is the beginning of tooth demineralization.  physical property ,Configuration of Monosaccharides  Asymmetric Carbon  Definition : A carbon atom is asymmetric if it is attached to four different chemical groups.  All monosaccharides except dihydroxy acetone contain asymmetric carbon atom.  Any substances containing asymmetric carbon atom show stereoisomers. Stereoisomers:  are group of compounds similar to each other in being composed of identical chemical groups but differ in spatial arrangement of these groups D and L form :  There two forms of monosaccharides according to the attachment of OH group to the carbon atom next to the last (adjacent to the alcoholic group ). If OH group is attached to the right side , the sugar is called D-sugar, but if attached to the left side, the sugar is L-sugar.Almost all naturally occurring carbohydrates are of D- configuration. CHO CHO H C OH HO C H CH2OH CH2OH D-Glyceraldehyde L-Glyceraldehyde OH group on sub-terminal OH group on sub-terminal carbon is written on right side. carbon is written on left side. As well as stereoisomers, as sugars are cyclisized, a second asymmetrical centre is created, giving two forms:  α and β form : If OH group at carbon 1 is on the right side,(below the plane in the ring form), this is called α form , but if it is on the left side ( above the plane in the ring form), it is called β form.  N.B: α and β forms can interconvert in solution (mutorotation): equilibrium 66% β, 33% α, 1% open chain. Epimers  They are isomers differ in distribution of OH group around asymmetric carbon atoms within the chain.  As : galactose C4 OH at left side and Glucose C4 OH at right side.  Mannose C2 OH at left side and Glucose C2 OH at right side 1-Epimer of glucose is: (A) Fructose (B) Mannose (C) Ribose (D) Glyceraldhyde  2.---------- is sugar of semen :   a) glucose. b) Mannose.   c) fructose. d) galactose.  3. The sugar does not contain asymmetrical carbon arom is ….  4 The reference sugar is …………..