L2-Carbohydrates (2 hrs) Lecture Notes PDF

Lec. 2: Carbohydrates Randa A. Zghloul Faculty of pharmacy Mansoura University, Mansoura, Egypt 2024-2025 Biochemistry-1 1  So Far !...

Lec. 2: Carbohydrates Randa A. Zghloul Faculty of pharmacy Mansoura University, Mansoura, Egypt 2024-2025 Biochemistry-1 1  So Far ! Recap ✓ What is Biochemistry 1 all about ! ✓ How to identify a molecule belonging to carbohydrates? ✓ How to classify them? ✓ What are monosaccharides? ✓ Most important monosaccharides? ✓ Classifications? ✓ …… and Properties? 2024-2025 Biochemistry-1 2  Learning objectives: to learn” Derivatives of Monosaccharides? Disaccharides Polysacchrides? 2024-2025 Biochemistry-1 3  Amino sugars: These are sugars in which the hydroxyl group of the second carbon is replaced v by an amino group. Glucosamine = (chitosamine) found in the shells of insects and hyaluronic acid and heparin and heparan (GAGs). Galactosamine = (chondrosamine) found in chondroitin (GAGs). 2024-2025 Biochemistry-1 4  Deoxy sugars These are sugars in which one of the OH groups is replaced by hydrogen atom. Ribose = in RNA synthesis Deoxyribose = in DNA synthesis 2024-2025 Biochemistry-1 5  Methyl sugar: These are sugars in which (C6)- CH2OH is replaced by -CH3 → sugar is called methylose ✓ Galactose → fucose. ✓ Glucose → Methyl pentose or Methylose 2024-2025 Biochemistry-1 6  Sugar alcohols These are sugars produced from reduction of monosaccharides, e.g. Inositol → cyclic compound derived from glucose in which aldehyde group is converted to a 2ry alcohol group CH-OH with linkage of C1 and C6. Myo-inositol (or muscle sugar) is present in muscle. 2024-2025 Biochemistry-1 7  They are sugars containing COOH group. Sugar acids Aldonic acids Aldehyde group is oxidized to COOH group by mild oxidizing agent e.g. Bromine water ❑ Glucose → gluconic acid ❑ Glyceraldehyde → glyceric acid. ❑ L-ascorbic acid is also an aldonic acid. 2024-2025 Biochemistry-1 8  Sugar acids Uronic acids: Last -CH2OH group is oxidized to COOH group by moderate oxidizing agent e.g. hydrogen peroxide e.g. glucuronic acid from glucose and galacturonic acid from galactose. 2024-2025 Biochemistry-1 9  Sugar acids Aldaric Saccharic acids: both aldehyde group and the last -CH2 OH group by strong oxidizing agent e.g nitric acid e.g. aldaric (glucaric or saccharic) acid from glucose and mucic acid from galactose 2024-2025 Biochemistry-1 10 2024-2025 Biochemistry-1 11  Derived monosaccharides (monosaccharide derivatives) 2024-2025 Biochemistry-1 12  2- Oligosaccharides sugars composed of 2:10 monosaccharide residues united together by glycosidic linkages (HC-O-CH). oligosaccharides are classified into disaccharides, trisaccharides, etc …. Disaccharides: Reducing disaccharides: Maltose Lactose Cellobiose - 2 α-glucose -glucose+ β-galactose - 2 β-glucose - by α, 1-4 glycosidic linkage. -by β, 1-4 glycosidic linkage. - by β, 1-4 glycosidic linkage. - Free aldehyde →Reducing w -Milk sugar →Reducing w - Reducing sugar→ Repeating characteristic osazone. characteristic osazone. units in cellulose in plants. - It can be hydrolyzed by: 1- It can be hydrolyzed by: 1- acid, - it results from the careful acid, 2- maltase enzyme 2- lactase enzyme hydrolysis of cellulose. Not fermented by yeast. 2024-2025 Biochemistry-1 13  Non reducing disaccharides: Sucrose (Cane sugar): Properties It occurs free in most fruits and vegetables. Called invert sugar as naturally it is dextro-rotatory but → on hydrolysis it gives a levo-rotatory mixture of equal amounts of Formed from α- glucose and fructose [although equal but L-rotation of fructose > D- glucose+β-Fructose rotation of glucose]. by α,1-β,2 glycosidic This occurs in yeast by enzyme called invertase linkage 2024-2025 Biochemistry-1 14  2- Oligosaccharides Trisaccharides= 3 monosaccharide units. Tetrasaccharides= 4 monosaccharide units e.g. Raffinose = galactose + glucose + fructose e.g. Stachyose = 2 galactose + glucose + fructose. 2024-2025 Biochemistry-1 15  3- Polysaccharides Definition Classification Polymers of > 10 Homogenous polysaccharides (Homopolysaccharides): On hydrolysis monosaccharide they yield the same type of monosaccharide units. residues, united by glycosidic Heterogeneous polysaccharides (Heteropolysaccharides): made of linkages. two or more different monosaccharides.. 2024-2025 Biochemistry-1 16 A- Homogenous polysaccharides: They are either: Hexosan Pentosans Glucosan Fructosan On hydrolysis they yield On hydrolysis yield only On hydrolysis yield only pentoses units. glucose units fructose units chiefly in vegetable gums e.g. Starch, Dextrins, e.g. Inulin. e.g. cherry gums yields Dextran, Glycogen & arabinose. Cellulose. 2024-2025 Biochemistry-1 17 1-Starch 2- Glycogen Storage form →in plants. storage form → in animals non reducing → no free aldehyde/ketone mainly in liver and muscles Branched Polymer of -glucose units Branched polymer of -glucose units linked: by -1,4 & -1,6 glycosidic linked: by -1,4 & -1,6 glycosidic linkages linkages consists of 2 components: Structure: similar to amylopectin of starch. Amylose: (inner part): (< 25%) Similarity: Straight-chain polymers of -glucose both have α-glucose units linked by  1,4- glycosidic linkage. linked by α-1,4 & α-1,6-bonds at the branching points, Amylopectin (outer part): (about 75%) branched polymer of (24-30) -glucose Differences: linked by 1,4 glycosidic linkage, but at it contains more numerous branches the points of branches, the linkage is α but shorter branches (8-12 units) than 1,6- glycosidic. amylopectin. 2024-2025 Biochemistry-1 18  Amylose Amylopectin/glycogen 2024-2025 Biochemistry-1 19 3- Dextrins 4- Dextrans: Partial hydrolytic products of starch. Produced by certain bacteria allowed to grow on sugar media. Polymer of α-glucose units linked by: Polymer of α-glucose units linked by: α -1,4 & α-1,6 glycosidic linkages. α -1,4 & α-1,6 & & α-1,3 linkages. Uses: Uses: in infant feeding, Plasma substitute in case of hemorrhage as adhesives and binders to ↑ the volume of circulating blood. → ↑ They include: amylodextrins, viscosity, ↓ osmotic pressure and slow erythrodextrins & achrodextrins. disintegration mimicking the lost blood 2024-2025 Biochemistry-1 20 5- cellulose 6- Inulin (Tructan-Fructosan):: Structural form → plant cells. Storage form → in the tubers & roots of It constitutes the cell walls fruits - dietary fibers Linear polymer of -glucose units Linear polymer of β-D-fructose units linked by -1,4 glycosidic linkages. linked by β(2,1) linkages. It cannot be digested by humans It cannot be digested by humans & if (cause of -glucosidic linkage): no injected I.V.→ it is not metabolized. nutritive value. Uses: Medical uses prevents constipation → Forms the bulk Diet for Diabetics. of stools, stimulate peristalsis. Measures the Glomerular filtration rate as medium for intestinal flora [required (GFR) → (not absorbed by renal tubules). for vitamin B formation]. Determination of the Extracellular fluid Partial hydrolysis by acids→ cellobiose volume Complete hydrolysis→ β-glucose.. 2024-2025 Biochemistry-1 21 2024-2025 Biochemistry-1 22  Learning objectives: to learn” Derivatives of Monosaccharides? Disaccharides Polysacchrides? 2024-2025 Biochemistry-1 23  Thanks 2024-2025 Biochemistry-1 24