Carbohydrates Chemistry PDF

‫ب ِّز ْد ِّني‬ ‫ُ‬ ‫َوقل َّر ِّ‬ ‫ْ‬ ‫ِّعل ًما‬ ‫سورة طه ‪ -‬اآلية ‪114‬‬ Carbohydrate Chemistry Directed by Pro.Dr/ Maathir kamel  IIntended learning outcomes (ILOs) A) Knowledge and Understanding By the end of the course, students...

‫ب ِّز ْد ِّني‬ ‫ُ‬ ‫َوقل َّر ِّ‬ ‫ْ‬ ‫ِّعل ًما‬ ‫سورة طه ‪ -‬اآلية ‪114‬‬ Carbohydrate Chemistry Directed by Pro.Dr/ Maathir kamel  IIntended learning outcomes (ILOs) A) Knowledge and Understanding By the end of the course, students should be able to: Define the importance and types of carbohydrates Illustrate the classification of monosaccharides Enumerate the monosaccharide derivatives and describe their structure and functions. B-Professional and Practical Skills Identify the physical properties of carbohydrates  Carbohydrates Carbohydrates (CHO) are aldehyde or ketone derivatives of polyhydric alcohols or any substances derived from them.  Importance of Carbohydrates Glucose is the major fuel of the mammalian tissue. Oligo- and polysaccharides are important constituents of cell membranes. Cellulose forms the cell walls of plants and is important in diet, preventing constipation. Mucopolysaccharides are important components of connective tissues. Heparin is the most important natural anticoagulant. Carbohydrates may combine with lipids forming glycolipides or protein forming glycoproteins  Classification of Carbohydrates Carbohydrates are classified according to the hydrolytic products as follows: (A) Monosaccharides: ▪ They cannot give simpler forms on hydrolysis. ▪ They are composed of one sugar unit ▪ They are subdivided into; Trioses, tetroses, pentoses, hexoses, heptoses or octoses depending upon the number of carbon atoms. (B) Disaccharides: ▪ They are composed of 2 sugar units; sucrose, lactose and maltose. (C) Oligosaccharides: ▪ These are carbohydrates which are composed of or give 3-10 monosaccharide units on hydrolysis. (D) Polysacchandes: ▪ These are carbohydrates which are composed or give more than 10 monosaccharide units on hydrolysis; starch and dextrins.  MONOSACCHARIDES ▪ Monosaccharides have the general formula Cn(H2O)n. ▪ There are many classifications of monosaccharides: ❑The presence of aldehyde or ketone groups into: ❖Aldoses e.g: glycerose, erythrose, ribose & glucose ❖ketoses e.g: dihydroxyacetone, erythrulose, ribulose & fructose. ❑The number of carbon atoms as: (1) Trioses: ❖They contain three carbon atoms. ❖They are formed in the course of the breakdown of glucose by the glycolysis pathway and by the pentose phosphate pathways. (2) Tetroses: ❖These contain four carbon atoms. ❖Tetroses are formed during breakdown of glucose by the pentose-phosphate pathway. (3) Pentoses: ❖These contain five carbon atoms. ❖Pentoses are formed during the breakdown of glucose via the pentose-phosphate pathway. ❖They are important constituents of nucleotides, nucleic acids and many enzymes. (4) Hexoses: ❖These monosaccharides contain 6 carbon atoms. ❖The physiologically important hexoses are glucose, galactose, fructose and mannose.  Glucose It is the most important sugar of carbohydrates It results from the hydrolysis of starch, cane sugar, maltose and lactose. It is converted to all carbohydrates in the body e.g galactose, ribose and glycogen. Glucose is the sugar carried by the blood and is the principal sugar used by the tissues. It is the major source of energy. It is present in urine in cases of diabetes mellitus due to raised blood glucose.  Fructose It is present in fruit juices and honey. It results from the hydrolysis of cane sugar and of inulin. Fructose can be changed to glucose in the liver and intestine, so it can be used in the body. It is the sugar of semen.  Galactose It is formed during hydrolysis of lactose (milk sugar). It can be metabolized to glucose. It is formed in the mammary gland to make the lactose of milk. It is a constituent of glycolipids and glycoproteins. Mannose It is formed during the hydrolysis of gums. It is a constituent of many glycoproteins.  PHYSICAL PROPERTIES OF MONOSACCHARIDES A-Monosaccharides are colorless, crystalline and sweet substances. B-Sugars exhibit various forms of isomerism. Definition: Isomers are compounds having the same structural formula but differ in spatial configuration. – The formation of isomers is caused by the presence of asymmetric carbon atoms What is asymmetric carbon atom? It is the carbon atoms which attached to 4 different atoms. – The number of possible isomers of a compound depends on the number of asymmetric carbon atoms (n) and is equal to 2n. – For example, glucose has 4 asymmetric carbon atoms, so the number of isomers = 16 isomers.  Types of isomerism : (1) D and L isomers (2) Alpha and beta anomers (3) Epimers (4) Aldoses and Ketoses  D and L isomers This type of isomerism depends upon the orientation of the -H and -OH groups around the subterminal carbon atom. When the -OH group is on the right, the sugar is a member of the D-series, when it is on the left, It is a member of the L-series. Most of the monosaccharides occurring in mammals are of the D-configuration. O H O H C C H – C – OH HO – C – H HO – C – H H – C – OH H – C – OH HO – C – H H – C – OH HO – C – H CH2OH CH2OH D-glucose L-glucose  Alpha and beta anomers These are isomers differing in the configuration of -OH and -H on C1. The ring structure of an aldose is formed by combination of an aldehyde (C1) and alcohol groups forming hemiacetal ring. The cyclic structure is retained in solution, but isomerism takes place about the carbonyl or anomeric carbon atoms (C1) to give either alpha-glucopyranose (38%) or beta- glucopyranose (62%). α and β anomers  Epimers These are isomers differing in the configuration of the -OH and -H on carbon atoms 2, 3 and 4 of glucose. The most important epimers of glucose are mannose and galactose. Mannose is formed by epimerization at carbon 2 whereas, galactose by epimerization at carbon 4.  Aldoses and ketoses Definition: - These are isomers depending on the presence of aldhyde or ketone group. Example: - Glucose and fructose.  Derivatives of monosaccharides 1.Deoxy sugars :- Definition:- These are sugars in which the hydroxyl group is replaced by a hydrogen atom. Example:- Deoxy ribose from ribose :- used in DNA 2.Amino sugars (hexosamines):- Definition:- These are sugar in which the OH group of the second carbon is replaced by an amino group (NH2). Examples:- Glucosamine:- Enter is structure of hyaluronic acid Galactosamine:- Chondrotin sulfate Mannosamine :- Erythromycin. 3.Sugar acids i-Uronic acid:- Definition:- It is an acid that results from oxidation of the primary alcohol group ( the last carbon) of aldoses to carboxyl group. Example :- Glucouronic acid from glucose. ii- Aldonic acid It is an acid that results from oxidation of aldhyde iii.Aldaric sugar:- Definition:- It is an acid that results from oxidation of both aldhyde and primary alcohol groups of aldoses to carboxyl groups. Example :- Glucaric(saccharic ) acid from glucose 4.Glycosides :- Definition: - Glycosides are compounds resulting from condensation of sugars with another compound which may or may not be another sugar. Cyclic form of monosaccharides