Basics of Carbohydrate Chemistry PDF

Basics of Carbohydrate Chemistry By: Dr.B.K.Manjunatha Goud MBBS MD Professor and Chairperson of Biochemistry Time: 09.35am-10.35am Date:20/01/2025  Learning outcomes Classify carbohydrates with examples. List the Physiological funct...

Basics of Carbohydrate Chemistry By: Dr.B.K.Manjunatha Goud MBBS MD Professor and Chairperson of Biochemistry Time: 09.35am-10.35am Date:20/01/2025  Learning outcomes Classify carbohydrates with examples. List the Physiological functions of each. Understand the clinical importance of various carbohydrates.  Case 1 A 50 year old diabetic having complaints of decreased vision. On investigation found to have abnormally high levels of blood glucose and Eye examination reveled lens changes. The doctor suspected of following condition________ Abnormally increased levels of following substance in lens may have led to this condition__________  Case 2 A 25 year old boy brought to emergency department with loss of consciousness and altered sensorium. On examination found to have increased intracranial tension. The substance that can be used treat this condition is_________  Carbohydrates These are most abundant organic molecules They primarily consists of carbon, hydrogen, oxygen. The general formula for Cn(H2O)n.  Carbohydrates Carbohydrates are polyhydroxy aldehydes or ketones, or substances that yield such compounds on hydrolysis  Functions Gives energy 4Kcal/gram Storage form Constituent of nucleotide and nucleic acids Important component of milk Structural component of cell Cardiac glycosides Antibiotics Dietary fiber Intravascular anticoagulant  Classification 1. Monosaccharide's. (3-9 carbon residues) 2. Disaccharides. ( 2 monosaccharide units) 3. Oligosaccharides.(3-10 monosaccharide units) 4. Polysaccharides. (>10 monosaccharide units)  Monosaccharide's Simplest group of carbohydrates which cannot be further hydrolyzed. Mono-means one, Saccharides- means sugar When functional group is an Aldehydes they are known as Aldoses (glucose) When functional group is an Keto they are known as ketoses (Fructose)  Aldoses and Ketoses Glyceraldehyde Dihydroxyacetone Erythrose Erythrulose Arabinose Ribulose Glucose Fructose  Monosaccharide's # Carbons Category Name Relevant examples 3 Triose Glyceraldehyde, Dihydroxyacetone 4 Tetrose Erythrose 5 Pentose Ribose, Ribulose, Xylulose 6 Hexose Glucose, Galactose, Mannose, Fructose 7 Heptose Sedoheptulose  Structural aspects of Monosaccharide's Configuration of sugars can be represented either by Fischer or by Haworth projection formulae. Haworth projection formulae are depicted by a six membered ring resemble the organic molecule pyran and are termed pyranoses or a five membered furan and are termed furanoses.  Pyranose and Furanose Because of the tetrahedral nature of carbon bonds, the cyclic form of pyranose sugars actually assume a "chair" or "boat" configuration, depending on the sugar Fischer and Haworth projection  Isomerism in carbohydrates 1. Functional isomerism 2. Stereoisomerism a) Enantiomers b) Optical isomers c) Pyranose and furanose isomers d) Anomers e) Epimers  Asymmetric carbon atom When a carbon is attached with 4 different groups or atoms is called asymmetric (chiral center). Glyceraldehyde the reference CHO a triose is the simplest monosaccharide with one asymmetric carbon atom and glucose has 4 asymmetric carbons. Stereoisomer's Compounds have the same chemical formula but differ in the positions of the hydroxyl groups on their asymmetric carbons (in blue) For example: glucose, mannose, Galactose and fructose, have the same chemical formula, C6H12O6. Enantiomers Carbohydrates can exist in either of two conformations, as determined by the orientation of the hydroxyl group about the asymmetric carbon adjacent to the terminal primary alcohol carbon. carbohydrates that are of physiological significance exist in the D-conformation. Epimers Carbohydrates that differ from each other in their configuration around a single specific carbon atom only in the position of the –OH group (other than anomeric carbon C1) are defined as Epimers. Example: Glucose and Mannose are Epimers with regard to C-2. Glucose and Galactose are Epimers with regard to C-4. Anomers Cyclization creates an anomeric carbon generating α and β configuration called Anomers. Example: α Glucose and β Glucose are Anomers which differ from each other only around C1 known as anomeric carbon. In Haworth projection: α -configuration, OH is trans to the CH2OH group. β -configuration, OH is cis to the CH2OH group  Properties of sugars Muta rotation Reducing property Osazone formation Oxidation of sugars Reduction to form alcohols Glycosides Formation of esters  Mutarotation When D glucose is crystallized at room temperature, and a fresh solution is prepared, its specific rotation of polarized light is +112o; but after 12–18 hours it changes to +52.5o. If initial crystallization is taking place at 98oC and then solubilized, the specific rotation is found to be +19o, which also changes to +52.5o within a few hours. This change in rotation with time is called mutarotation.  Answer When glucose solution is freshly prepared, most of the molecules are in a-form. On keeping the solution for 18 hours, "mutarotation" takes place, and 63% molecules are changed to b-configuration  Optical isomers Are pair of isomers that differ in the direction in which they rotate the plane polarized light Ex: Dextrorotatory (+) and levorotatory (-) Dextrose Levulose  Chemical properties of sugars Reducing sugars Are the sugars which has free aldehyde or keto group at the anomeric carbon atom Benedict’s test Clinical significance, Diabetes Mellitus Lactosuria Galactosuria Fructosuria  Reactions of monosaccharides Under mild oxidation conditions, the aldehyde group is oxidized to carboxyl group to produce aldonic acid. Thus, glucose is oxidized to gluconic acid, mannose to mannonic acid and galactose to galactonic acid. When aldehyde group is protected, and the molecule is oxidised, the last carbon becomes COOH group to produce uronic acid. Oxidation of -CH2OH group Glucose ---------→ Glucuronic acid ( Detoxification of bilirubin) Galactose ------→ Galacturonic acid Components of Glycosaminoglycans  2.Oxidation of –CHO group Converted to their respective aldonic acids Glucose -------→ Gluconic acid Mannose ---------Mannonic acid Galactose---------Galactonic acid  Reduction reactions Reduction of aldehyde or keto group produces new alcohol group Glucose -----→ Sorbitol Galactose -----→ Dulcitol Mannose ------→ Mannitol  Deoxy sugars These are the sugars that contain one oxygen less than that present in the parent molecule Ribose ---------→ 2- Deoxy ribose  Glycosides Compounds formed by condensation of –OH group at anomeric carbon of a monosaccharide with a second group which may or may not be a monosaccharide O and N – Glycosides Ex: Digitonin---- Cardiac stimulant Digoxin----- Treatment of CCF Streptomycin, Doxorubicin  Amino sugars Hydroxyl group is replaced with amino group forming amino sugar Glucosamine Galactosamine Mannosamine Important compounds found in connective tissues. Reference Book: Text book of Biochemistry By DM Vasudevan 6th and 8th edition Integrated text book of Biochemistry by Indumati V 1st edition Text book of Biochemistry, Lippincott's Google images Thank you