Benha National University Biochemistry Lecture - Carbohydrate Chemistry PDF

Biochemistry Lecture Carbohydrate Chemistry 10/5/2024 Prof. Dr. Inas Abd Elmonem  Presented by Prof. Dr. Inas Abd Elmonem Assistant professor of Medical Biochemistry...

Biochemistry Lecture Carbohydrate Chemistry 10/5/2024 Prof. Dr. Inas Abd Elmonem  Presented by Prof. Dr. Inas Abd Elmonem Assistant professor of Medical Biochemistry Department 10/5/2024 Prof. Dr. Inas Abd Elmonem  Objectives By the end of this lecture, the students will be able to:  Define carbohydrates.  Classify carbohydrates.  Classify monosaccharides.  Identify hexoses of physiological importance.  Identify biomedical importance of lactose.  Classify polysaccharides.  Identify biomedical importance of glycogen.  List the monosaccharide derivatives 10/5/2024 Prof. Dr. Inas Abd Elmonem  Definition: Carbohydrates (CHO) are organic compounds consisting of carbon, hydrogen and oxygen atoms. They are polyhydroxy aldehydes, polyhydroxy ketones, or compounds that yield such substances upon hydrolysis. 10/5/2024 Prof. Dr. Inas Abd Elmonem  Classification of carbohydrates: According to the number of sugar units, CHO, can be classified into: Monosaccharides: They are the simplest structural unit of carbohydrates that CANNOT be hydrolysed into smaller one. Condensation products of two monosaccharide units. Disaccharides: Oligosaccharides: They are condensation products of three to ten monosaccharides. Polysaccharides: They are condensation of more than ten monosaccharide units. 10/5/2024 Prof. Dr. Inas Abd Elmonem 10/5/2024 Prof. Dr. Inas Abd Elmonem 10/5/2024 Prof. Dr. Inas Abd Elmonem  They are classified according to the number of carbon atoms per molecule into: 1.Trioses: The smallest monosaccharide, they contain 3-carbon atoms per molecule e.g., Glyceraldehyde and Dihydroxyacetone. 2.Tetrose: Monosaccharide with 4 carbon atoms per molecule e.g. Erythrose and Erythrulose. 3. Pentoses: Contain 5-carbon I. Monosaccharides atoms/molecule e.g., ribose, deoxyribose and ribulose. Ribose and Deoxyribose are the two common pentoses found in RNA and DNA, respectively. 4. Hexoses: Contain 6-carbon atoms per molecule e.g., Glucose, Galactose and Fructose. 10/5/2024 Prof. Dr. Inas Abd Elmonem  1-Glucose (Grape sugar): Physiological Importance of glucose : a. It is the blood sugar: The main metabolic fuel used by tissues b. Enters in the formation of many disaccharides and polysaccharides. c. Used in diagnosis of diabetes mellitus. Hexoses of 2-Galactose: Physiological importance of galactose: a. Galactose is used for synthesis of lactose (milk sugar) from physiological glucose, in the mammary glands. b. Synthesis of glycoproteins found in brain and nerve tissue. importance c. Distinguish various types of blood groups А, В, АВ, and O group. 3-Fructose (fruit sugar): Physiological importance of fructose : a. The sweetest tasting of all sugars. It is sometimes used in stead of table sugar for sweetening, not because it has fewer calories per gram than other sugars but because less is needed for the same amount of sweetness. b. Synthesis of sucrose (glucose+ fructose). c. It is the main sugar in seminal fluid. 10/5/2024 Prof. Dr. Inas Abd Elmonem  Definition: They are products of condensation of 2 monosaccharide units. The bond between the two monosaccharide is glyosidic bond. II. Disaccharides Important disaccharides include: Maltose: Glucose+ Glucose Lactose (milk sugar): Glucose + Galactose Sucrose (table sugar): Glucose + Fructose 10/5/2024 Prof. Dr. Inas Abd Elmonem 10/5/2024 Prof. Dr. Inas Abd Elmonem  Biomedical importance of lactose : It is the most suitable sugar in milk for infants because: 1. Lactose contains galactose which is vital to a healthy brain and nerve tissues. Lactose in breast milk is considered as the only source of galactose during the early months (an important time of rapid brain growth and development). 2. Lactose also contains glucose which is essential for energy, growth and cell development. Without glucose in the diet, baby will use body fat as a source of energy and lose weight. 3. It is less sweaty than sucrose, so allows babies to take large amounts of it without nausea. 4. Laxative so prevent constipation. 5. lactose helps growth of lactic acid producing bacteria, lactic acid helps absorption of Ca++, phosphorus, iron and copper 6. It is non-fermentable (not fermented by yeast) so it doesn’t produce CO2 in the small intestine and the baby doesn’t suffer from abdominal colic or distention. 7. It also inhibits growth of putrefactive bacteria because it makes acidic medium in the intestine. 10/5/2024 Prof. Dr. Inas Abd Elmonem  Definition: They are polymers of more than 10 monosaccharide units. Classification of Polysaccharides: According to Composition: Homopolysaccharides: They are composed of III. Polysaccharides repeated units of the same type of monosaccharide units e.g., starch and glycogen. Heteropolysaccharides: They are polysaccharide which are formed of more than one type of monosaccharides. 10/5/2024 Prof. Dr. Inas Abd Elmonem 10/5/2024 Prof. Dr. Inas Abd Elmonem  Starch Glycogen Cellulose Functions 1. Storage form of 1. Storage form of carbohydrates in 1. Cellulose in diet → increases the bulk of carbohydrates in plants. animals (Stored mainly in liver and stool → stimulate intestinal peristalses→ muscle). prevent constipation (laxative). 2. Major source of carbohydrates for 2. Liver glycogen maintains normal 2. Cellulose is a constituent of dietary fibers→ animals. blood glucose concentration These fibers help to ↓ absorption of toxic especially during the early stage of compounds & ↓ the incidence of cancer fasting (between meals). After 12 -18 colon. hours fasting, liver glycogen is 3. Cellulose can be utilized & serve as a source depleted. of energy in herbivores because their gut 3. Muscle glycogen acts as a source of contains bacterial enzyme that can attack β- energy within the muscle itself linkage. especially during muscle contraction. 4. Supportive in plants 10/5/2024 Prof. Dr. Inas Abd Elmonem  Quiz 2. Which of the following are the product 1. Which of the following are the product of lactose of sucrose hydrolysis? hydrolysis? a. Only glucose a. Two molecules of glucose b. Only galactose b. Glucose and fructose c. Galactose and glucose c. Glucose and galactose d. Glucose and mannose d. Fructose and glucose e. Galactose and mannose e. Only fructose 3. Which of the following carbohydrate is 4. Which of the following is the storage considered dietary fiber? form of carbohydrate in animals? a. Glycogen a. Starch b. Starch b. Dextrans c. Dextrins c. Chitin d. Cellulose d. Cellulose e. Lactose 10/5/2024 Prof. Dr. Inas Abd Elmonem e. Glycogen Derivatives of Monosaccharides Sugar Phosphates Deoxy Sugars Amino Sugars SugarAlcohols Sugar Acids AscorbicAcid 17  Monosaccharides in metabolic pathways are often A. Sugar converted to phosphate esters. The triose phosphates, ribose 5-phosphate, and glucose Phosphates 6-phosphate are simple alcohol-phosphate esters. 18 B. Deoxy A hydrogen atom replaces one of the hydroxyl groups in the parent monosaccharide, e.g. 2-Deoxy-D-ribose is an important building block for DNA. Sugars L-Fucose (6-deoxy-L-galactose) is widely distributed in plants, animals, and microorganisms. 19 C. Amino In a number of sugars, an amino group replaces one of the hydroxyl groups in the parent monosaccharide. Sometimes the amino group is acetylated. Three Sugars examples of amino sugars are shown below: 20  In a sugar alcohol, the carbonyl oxygen of the parent monosaccharide has been D. Sugar reduced, producing a polyhydroxy alcohol. Three examples of sugar alcohols. Glycerol and myo- inositol are important components of lipids Ribitol is a component of flavin mononucleotide (FMN) and Alcohols flavinadenine dinucleotide (FAD) In general, sugar alcohols are named by replacing the suffix –ose of the parent monosaccharides with -itol. 21 E. Sugar Acids Sugar acids are carboxylic acids derived from aldoses, either by: 1. oxidation of C-1(the aldehydic carbon) to yield an aldonic acid, Or by 2. oxidation of the highest- numbered carbon (the carbon with the primary alcohol) to yield an alduronic acid. The structures of the aldonic and alduronic derivatives of glucose are gluconate and glucuronate, respectively. F.Ascorbic Acid L-Ascorbic acid, or vitamin C, is an enediol of a lactone derived from D- glucuronate. Primates cannot convert glucuronate to ascorbic acid and must therefore obtain ascorbic acid from the diet. Ascorbic acid is an essential cofactor for the enzymes that catalyze the hydroxylation of proline and lysine residues during collagen synthesis 10/5/2024 Prof. Dr. Inas Abd Elmonem 10/5/2024 Prof. Dr. Inas Abd Elmonem