Carbohydrate Chemistry 1st Year Dental Students 2024 PDF

Biochemistry 1st year dental students Carbohydrates Chemistry DR Siham Abbas 2024 1 Objectives: 1-Define and Classify Carbohydrates. 2-Outline the biomedical importance of carbohydrates. 3Summarize the nomenclature of monosaccharaides. 4-List the biom...

Biochemistry 1st year dental students Carbohydrates Chemistry DR Siham Abbas 2024 1 Objectives: 1-Define and Classify Carbohydrates. 2-Outline the biomedical importance of carbohydrates. 3Summarize the nomenclature of monosaccharaides. 4-List the biomedical importance of monosaccharaides 5-Study general properties of monosaccharaides. 6-Study physical and chemical properties of monosaccharaides. 2 -Carbohydrates: are an organic compounds that consists of carbon, hydrogen, and oxygen. -The empiric formula for many of the simpler carbohydrates is (CH2O)n. -Glucose is the most important CHO. Classification of Carbohydrates 1-Monosaccharides are the simplest carbohydrates, and contain one sugar. e.g Glucose, fructose , galactose and mannose 3 - Disaccharides -Two joined monosaccharides e.g Maltose = Glucose + Glucose. -Oligosaccharides contain 3-10 sugar units e.g Maltotriose = 3 glucose. -Polysaccharides contain more than 10 sugar units e.g Starch and glycogen. 4 Biomedical importance of carbohydrates: -65% of our food should come from carbohydrates. 1.The major source of energy. 2.They serving as cell membrane components (glycolipids and glycoproteins). 3.Carbohydrates serve as a structural component of many organisms, including the cell walls of bacteria and the fibrous cellulose of plants. 4.Degradation products utilized for synthesis of other 5 substances such as fatty acids, and cholesterol. Monosaccharides: -They are the simplest units of carbohydrate (only one sugar unit). -General formula : CnH2nOn -They can not hydrolyzed into a simpler form. Classification of monosaccharides: 1.According to the number of carbon atoms they contain. 6 2-According to the type of carbonyl group they contain. -Carbohydrates with an aldehyde as their carbonyl group are called aldoses and those with a ketone group as carbonyl group are called ketoses. 7 -Glyceraldehyde is an aldose, whereas dihydroxyacetone is a ketose , the keto group is located at C-2 of the sugar 8 3-According to both presence of aldehyde or ketone groups and number of carbon atoms (aldotrioses and ketotrioses , aldotetroses and ketotetroses). 9 Biomedical importance of monosaccharaides: 1-Ribose and deoxyribose (pentoses): enter in the structure of nucleic acids RNA and DNA. 10 -Glucose (hexoses) is the most important sugar of CHO, the main sugar in blood, and the major source of energy in the body. -Fructose is the main sugar of semen. -Xylulose(ketoses) is an intermediate in HMP (hexose monophosphate pathway) and uronic acid pathway 11 Properties of monosaccharides: -Physical properties: 1-All monosaccharides are soluble in water, but insoluble in non-polar solvents. 2-All monosaccharides show the property of optical activity except dihydroxyacetone. 3-All monosaccharides can exist in α and β forms. 12 Chemical properties: 1-Oxidation: oxidation of sugar gives acid ( sugar derivatives). Oxidation of aldehyde group (CHO→ COOH) result in the formation of Gluconic acid. 2-Reduction: reduction of sugar gives alcohol such as D-glucose → D-sorbitol. D-galactose → D-dulcitol. D-fructose → D-mannitol+ D-sorbitol. 13 3-Reducing sugars: -Sugars containing free aldehyde or ketone group can reduce other reagents. E,g They can reduce cupric ions Cu2+ of fehling’s and Benedict’s reagents into cuprous ions Cu+ : Cupric (blue) + sugar → cuprous (red) + oxidized sugar -These tests are one of the earliest tests for sugar detection 14 in urine of diabetics. 4-Osazone formation: osazones are characteristic crystals resulting from the reaction of sugars with phenylhydrazine. -All sugars having free carbonyl group can form osazone crystals(The reaction can be used to identify monosaccharides). - Glucose, fructose and mannose form needle-shaped crystals. 15 General Properties : Isomers :are compounds that have the same chemical formula but have different structures. -For example: Glucose, galactose, mannose and fructose are all isomers of each other , having the same chemical formula, C6H12O6 16 Epimers: Two sugars (a sugar pair) that differ only in the configuration around one carbon atom are called epimers. Example -D-glucose and D-mannose are epimers. They differ only at the stereochemistry of C2. -Similarly, D-glucose and D-galactose are epimers. They differ around the stereochemistry of C4. 17  Note: -Galactose and mannose are NOT epimers. -They differ in the position of –OH groups at two carbons (2 and 4) and are, therefore, defined only as isomers 18 Asymmetric carbon atom (Chiral carbon): -The carbon atom attached to 4 different atoms or groups is called asymmetric carbon. 19 Enantiomers : A special type of isomerism is found in the pairs of structures that are mirror images of each other. The two members of the pair are designated as a D-and an L-sugar. Majority of the sugars in humans are D-sugars. D- isomer: -OH group on asymmetric carbon is on the right. L- isomer: -OH group on asymmetric carbon is on the left. 20  Optical activity: -Any substance containing asymmetric carbon atom show optical activity. It is the ability of a sugar to rotate plane polarized light either to the right or to the left -Glucose is dextrorotatory(+),while fructose is levorotatory(-) 21 22