Carbohydrate chemistry lecture 1 only.pdf

BMS: 131 Lecture No: 1 Title: Carbohydrate Chemistry Instructor Name: Dr Wael Elayat Medicine and Surgery Program Fall 2024  Intended learning Outcomes (ILOs): At the end of this lecture Define carbohydrates. State t...

BMS: 131 Lecture No: 1 Title: Carbohydrate Chemistry Instructor Name: Dr Wael Elayat Medicine and Surgery Program Fall 2024  Intended learning Outcomes (ILOs): At the end of this lecture Define carbohydrates. State the the importance of carbohydrates. List the types of some stereoisomers Identify different physical and chemical properties of monosaccharides and give examples Recognize clinical importance of derivavtives of monosaccharides  Carbohydrates Definition Carbohydrates are polyhydroxy-aldehydes, polyhydroxy ketones derivatives. Or Aldehyde or ketone derivative of polyhydroxy alcohol Or Organic compounds composed only of C, H& O. They are also called Saccharides. Poly OH Aldehyde (PHA) & Poly OH Ketones (PHK). Aldehyde Ketone Importance 1. Main energy source. 2. Serve a structural and protective role (Insoluble carbohydrate polymers “Mucopolysaccherides” ). 3. Lubrication of joints and tendons (Glycoproteins & Proteoglycans). Importance 4. Adhesion between cells and Recognition. 5. Glycoconjugates (Glycoproteins or Glycolipids). 6. Participate in:(Pentose Sugars). a) Nucleic Acids (DNA, RNA) b) Coenzymes (NAD, FAD) c) Regulatory molecules (cAMP, cGMP) d) High energy compounds (ATP, GTP). Carbohydrates Classification According to number of sugar units Monosaccharides: Which cannot hydrolyzed to simpler forms, consist of a single (PHA) or (PHK). Disaccharides: Which are formed from Two monosaccharide units, linked together by a glyosidic bond. Oligosaccharides: They are carbohydrates formed for 3 to 10 monosaccharide units. Polysaccharides: They are polymers of monosaccharides units > 10. They may be linear e.g. cellulose or branched e.g. glycogen. Classification of monosaccharides According to Active group no. of C atoms both : no. of C + Aldoses (-CHO) Trioses (3C) active group Tetroses (4C) Pentoses or ketoses (C=O) (5C) Hexoses (6C) Dihydroxyacetone. Glyceraldhyde ketotriose aldotriose  Classification of Monsaccharides 1- Number of carbon atoms No of Name Carbons Triose: Glyceraldehyde and 3 dihydroxyacetone 4 Tetrose: Erythrose 5 Pentose: Ribose Hexose: glucose, galactose, mannose 6 and fructose  Examples: 2- According to presence of aldehyde or ketone group. Aldoses: Aldehyde group: CHO Ketoses: Ketone group: C=O. 3- According to number of carbons and presence of aldehyde or ketone group: Examples: Aldotriose Ketotriose Dihydroxyacetone  Aldo-sugar Keto-sugar Trioses (C3) Dihydroxyacetone Tetroses (C4) Erythrose Erythrulose  Aldo-sugar Keto-sugar Pentoses Ribose Ribulose (C5) Glucose Hexoses Galactose fructose (C6) Mannose  Characters of monosaccharide: A- Physical characters: 1- Stereoisomers Isomers: Compounds that have same general formula (same number & type of atom) but, with different arrangements of atoms in space. Examples of sterioisomers: i) Aldo-keto Isomers Isomerase ii) Epimers Change in the position of OH around epimeric carbon. Epimers at C2 Epimers at C4 CHO CHO CHO HO C HOH H C OH H C OH HO C H HO C H HO C H H C OH H C OH HO C HOH H C OH H C OH H C OH C2 C4 CH2OH CH2OH CH2OH Mannose Glucose Galactose  Sugars having D- and L- isomers are usually mirror images and are called Enantiomers (Stereoismers). iii- Enantomer (or Mirror image isomer) (D & L Isomers) The best example is Glyceraldehydes which is present in 2 isomers D- and L- forms:  The first carbon is an aldehyde group. the middle C is a symmetric C atom & The last carbon is a 1ry alcoholic group The L-isomer has an OH attached to the left of asymmetric C atoms. The D- isomer having it at the right. N.B.: the D form is the physiologically predominant form Asymmetric carbon atom It is the carbon atom attached to 4 different chemical groups  More than 99% of pentoses and hexoses are present in acyclic form which is called Haworth formula: iv- Anomers ( & β) If the OH group of the anomeric carbon at right (down), the anomer is called α-form. If the OH of the anomeric carbon at left (up), it is β- form. The α & β isomers are called anomers. 2- Optical activity - Def.: It is the ability of this compound to rotate the Plane polarized light either to the right [dextrorotatory or d (+)] Or to the left [levorotatory or l (-)] - Causes of optical activity: Presence of asymmetric carbon N.B.: All monosaccharide are optically active except dihydroxyacetone (as it does not contains asymmetric carbon atom) DHA  -(L) Sugar Solution NicKol’s prism +(d) Plane polarized light A polarized light vibrating in a single plane perpendicular to the direction of propagation. Be Carful !!! The Two Enantiomers (D & L) Of A Compound Always Rotate The Light In Opposite Directions. But The Two Anomers (α & β) Of A Compound Rotate The Light In same Directions But In different degrees. B- Chemical Properties of Monosaccharides i- Reducing character: Due to the presence of free aldehyde orfree ketone group All the monosaccharides have reducing properties. (It will be discussed in practical) ii- Monosaccharides derivatives 1- OH is replaced by amino group Glucose glucosamine 2- OH is replaced by H: Ribose 2- deoxy ribose RNA DNA 3- Sugar acids : They are sugars that contain carboxylic group (COOH) by oxidation of monosaccharide Aldonic acid Uronic acid Saccharic acid -Oxidation of aldehyde C1 -Oxidation of last C6 CH2OH -Oxidation of both of aldehyde and last CH2OH Gluconic acid Glucuronic acid Glucaric acid 4- Sugar Alcohol (Reduction) The aldehyde or ketone group in monosaccharides can be reduced to the corresponding alcohol CHO or C=O CH2OH. Ribose Glucose Mannose Clinical application Sorbitol → Artificial sweeteners (to reduce weight). Mannitol →Reduce acutely raised intracranial pressure by its osmotic effect (ttt of brain odema) & as osmotic diuritic.  References for further readings Lippincott Illustrated Review Integrated system Lippincott Illustrated Review 6th edition Oxford Hand book of Medical Science 2nd edition Clinical Key Student THANK YOU