Carbohydrate Chemistry Lecture 2 (Fall 2024) - Galala University PDF

BMS: 131 Lecture No: 2 Title: Carbohydrate Chemistry Instructor Name: Dr Wael Elayat Medicine and Surgery Program Fall 2024  Intended learning Outcomes (ILOs): Studying this topic should enable you to: Classify the t...

BMS: 131 Lecture No: 2 Title: Carbohydrate Chemistry Instructor Name: Dr Wael Elayat Medicine and Surgery Program Fall 2024  Intended learning Outcomes (ILOs): Studying this topic should enable you to: Classify the types of disaccharides and give examples in each class and their characteristics. Recognize the general structure of disaccharides and polysaccharides Classify the types of polysaccharides.  Disaccharides Are 2 monosaccharides united together by glycosidic bond-on hydrolysis they give two simple sugars. Example Classification of disaccharides: 1- Maltose= glucose + glucose It is malt sugar 2- Lactose= glucose + galactose Main carbohydrate in milk. 3- Sucrose= glucose + fructose It does not contain a free carbonyl carbon so it is non-reducing. Sucrose 4- Lactulose It is a disaccharide that is formed of β-galactose and fructose, linked together by β- 1-4 glycosidic bond between C1 in Galactose and C4 of Fructose. - Importance of lactulose 1- Laxtive: it is not absorbable from the intestine, so it is used to create bulk in the stool due to its osmotic effect→ TTT of Constipation 2- it is useful for patients with liver disease , since it does not allow enough time for intestinal bacteria to produce ammonia in the intestine of patients that can not deal with NH3 due to their diseased liver.  Polysaccharides Homo Polysaccharides Hetero Polysaccharides Starch Present mainly in Glycogen extracellular matrix. Cellulose Importance: Glycogen : A branched polymer of glucose. It is the major storage form of CHO in animals. Formed of repeated glucose unit linked together by α 1-4 glycosidic linkage and α 1-6 linkage at the branch point. Starch : Major storage form of CHO in plants formed of repeated glucose unit. It is formed of 2 chains straight (amylose) and branched amylopectin. Cellulose : Form the wall of plant cell. It is formed of repeated glucose units linked together by β 1-4 glycosidic linkage)> It is NOT digested in human body due to absence of hydrolytic enzymes (β glycosidase enzyme) so it prevents constipation and form main bulk of stool B) Hetero-polysaccharides (Complex polysaccharides) 1- Nonsulphated glucosaminoglycans i- (Hyaluronic Acid) i. Hyaluronic acid (Not sulphated GAGs) It is one of Glucosaminoglycans (GAGs) or mucopolysaccharides. It is composed of alternating residues of D-glucuroinc acid and N-acetylglucosamine. It is a clear, highly viscous solution that serves as lubricant in the Synovial fluid of joints. It forms the Vitreous humor that fills the eye ball It forms Extracellular matrix of cartilage and tendons. Hyaluronic acid Hyaluronic acid Defect Osteoarthritis 2- Sulphated glucosaminoglycans 1. Heparin. 2. Heparan sulfate. Glucosamine 3. Keratan sulfate. 4. Chondroitin sulfate. 5. Dermatan sulfate. Galactosamine i- Heparin It is an anticoagulant , present in mast cells. It is repeated disaccharide units of *Glucosamine-so4 + Glucuronic  Iduronic acid (variable) ii-Heparan sulphate Similar To Heparin In Its Structure But It is More Acetylated And Less Sulphated 3. Keratan sulphate It is present as: Type I: Cornea. Type II: Cartilage. It is repeated disaccharide units of N-acetylglucos0amine-so4 + Galactose Mucopolysaccharidosis Autosomal recessive inherited diseases result from defects in the lysosomal enzymes responsible for metabolism of Membrane-associated Glucosaminoglycans lead to accumulation of them in lysosomes of the affected cells. →→ Skeletal deformities, mental retardation & early death  II. Glycoconjugates some carbohydrates are covalently bound to: Proteins (Proteoglycans & Glycoproteins) Lipids (Glycolipids “Lipopolysaccharides”)  1) Proteoglycans Macromolecules, formed of glucosaminoglycan chains covalently bound to a membrane or a secreted proteins The glycan (CHO) constitutes the greater proportion. GAGs are Formed of amino sugars + uronic acids. They are the major component of cartilage, where they confer strength to such structures and provide points of adhesion, recognition and information transfer between cells, or between cells & the extracellular matrix.  1) Proteoglycans Glucosaminoglycan Attach To The Protein Core Via a Trisaccharide linker Composed of Protein Glucosaminoglycan Galactose Galactose Xylose S The protein core Is coupled to The Trisaccharide linker via its serine residue by an O-glycosidic bond.  2) Glycoproteins The Oligosaccharides portion are smaller than the proteins. Present On Cell Surfaces (Cell Membrane) Or Extracellular (Plasma Proteins (Except Albumin).  3) Glycolipids & Lipopolysaccharides Oligosaccharides are covalently bound to lipids. Gangliosides are membrane lipids in eukaryotic cells, which is complexed with oligosaccharides. Some of these complexes are responsible for determination of blood groups. Lipopolysaccharides They are the glycolipids present on the outer surface of bacterial cell walls of some gram negative bacteria. These molecules are the main target of antibodies produced by the immune system against these bacteria Lipopolysaccharides of some bacteria are toxic to human and are called bacterial endotoxins. Toxic Shock !! Endotoxins are responsible for lowering blood pressure & production of toxic shock that accompanies infection with gram negative bacteria. 1-Which of the following is a non reducing sugar? A-Maltose B-Sucrose C-Lactose D-glucose E-galactose 2-Which of the following polysaccharides is not digested in human body? A- Starch B- Dexterin C- Glycogen D- Hyalouronic acid E- Cellulose  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