Carbohydrate Chemistry Lecture 1 2024 PDF

٢٨/٠٣/١٤٤٦ Biochemistry Carbohydrate Chemistry Dr. Mohamed Fouad Assistant professor of biochemistry and molecular biology ١ ٢٨/٠٣/١٤٤٦ Elements Similar to All Carbohydrates...

٢٨/٠٣/١٤٤٦ Biochemistry Carbohydrate Chemistry Dr. Mohamed Fouad Assistant professor of biochemistry and molecular biology ١ ٢٨/٠٣/١٤٤٦ Elements Similar to All Carbohydrates C H O Carbohydrates are “hydrates of carbon” are organic compounds containing carbon, hydrogen and oxygen (wrong definition) why‫؟؟؟؟‬ CH COOH 3 Glucose C2H4O2 C6H12O6 C6(H2O)6 C2(H2O)2 Acetic acid )not a carbohydrate( ٢ ٢٨/٠٣/١٤٤٦ Carbohydrates(CnH2nOn) can be: 1. Polyhydroxyaldehyde 2. Polyhydroxyketone ex. glucose ex. fructose So, Carbohydrate are aldehyde or ketone derivatives of polyhydroxy compounds. Source/Origin of carbohydrates Photosynthesis (is the opposite of) Energy Metabolism ٣ ٢٨/٠٣/١٤٤٦ Importance of Carbohydrates: Major source of energy. Constituents of cell membrane and cell wall. Used to store energy when needed. Present in glycoproteins & Glycolipids. Classification of Carbohydrates Carbohydrates Monosaccharides Disac Oligo Polysaccharides One sugar unit 2sugar units 10 – 3sugar units More than 10 units That cannot be on hydrolysis on hydrolysis on hydrolysis hydrolysized Raffinose: consist of glucose, galactose and fructose consider as oligosaccharide ٤ ٢٨/٠٣/١٤٤٦ Monosaccharides They are the simplest carbohydrate unites which can not be hydrolyzed to a simpler form. *General formula: (CH2O)n n≥3 Nomenclature 1. According to free carbonyl group in the sugar: – If monosaccharide contains aldehyde group (CHO)→ it's called aldose. – And if contain ketone group (c=o)→ it's called ketose. ٥ ٢٨/٠٣/١٤٤٦ 2. According to the number of carbon atoms: If sugar contains 3carbons → it's called triose، 4c→ tetrose 5c→ pentose 6c→ hexose 7c→ heptose 3. By combining the two methods 3c-Aldotriose -keto triose 4c-Aldotetrose -keto tetrose 5c-Aldopentose -keto pentose 6c-Aldohexose -keto hexose ٦ ٢٨/٠٣/١٤٤٦ Monosaccharide Triose Pentose Tetrose Hexoses ٧ ٢٨/٠٣/١٤٤٦ Uses and properties of Monosaccharides TRIOSES -3C simple sugars formed during the metabolic breakdown of hexoses in CHO metabolism. e.g. Glyceraldehyde (glycerose or reference sugar), Dihydroxyacetone. Tetroses Are 4-C sugars. Erythrose is an intermediate in the Hexose Monophosphate Shunt. ٨ ٢٨/٠٣/١٤٤٦ Pentoses are 5-C sugars. Most important are Ribose (for RNA synthesis) and Deoxyribose (for DNA synthesis) which are found in nucleic acids and in coenzymes as NAD,NADP,FAD and COASH. D-Ribulose is an intermediary in the pentose shunt. D-Lyxose is found in heart muscles. D-Xylose and D-Arabinose are components of glycoproteins. Hexoses Glucose (Grape sugar or Dextrose): because it is dextrorotatory and found in fruit juice Galactose Derived from lactose hydrolysis and it convert into glucose in liver Fructose (Levulose): found in fruits and honey Mannose: used in glycoproteins ٩ ٢٨/٠٣/١٤٤٦ Hexoses Asymmetric carbon atoms: Asymmetric carbon atom responsible Carbon atom All for the that attached monosaccharides isomerism to 4 different contain and the atoms or asymmetric optical groups. carbon atom(s) activity. except dihydroxy acetone. ١٠ ٢٨/٠٣/١٤٤٦ The number of asymmetric carbon atoms increase ,the number of isomers increases. The number of isomers =2n where n is number of asymmetric carbon. Glucose has 4 n so, it has 16 isomers ١١ ٢٨/٠٣/١٤٤٦ Isomerism: Compounds that have the same structural formula but differ in the spatial configuration. Optical Stereo isomerism isomerism Aldo and Epimerism Furanose and α and β D,L Keto pyranose Form ١٢ ٢٨/٠٣/١٤٤٦ Optical Activity & Isomerism Optical activity: It is the ability of a substance to rotate the Plane.polarized light (PPL) either to the right or to the left If the substance rotate PPL to the right this substance is called dextrorotatory substance (D) or If the substance rotate PPL to the left this substance is called levorotatory substance or (L). All monosaccharides are optically active expect.dihydroxyacetone Most monosaccharide in mammals are D-Form ١٣ ٢٨/٠٣/١٤٤٦ The direction of rotation is independent of the stereochemistry of the sugar, so it may be designated For example dextrorotatory sugar (D or +): glucose, galactose and starch levorotatory sugar) L or:(-.invert sugarfructose and Optical Activity can be measured using POLARIMETER POLARIMETER ١٤ ٢٨/٠٣/١٤٤٦ Racemic mixture: Mixture of 2 different optical isomers (one dextrorotatory and other levorotatory) in an 0 equal amounts so it has an angel of rotation =.so it not show optical activity The separation of these two compounds from * each others is called resolution Mutarotation It is a change in specific rotation of a freshly prepared sugar when left in a solution (water) for few hours. The fresh solution of D-glucose has a rotatory power of +112.5 but on standing it gradually decreased till it reaches to a constant value of+ ، 52.5this is because in freshly prepared glucose the alpha anomer exists alone which has specific rotation of + 112.5, on standing some are transformed to beta forms which has a rotation of.19 + ١٥