BIOC201_CHO Chemistry [Series 1].pdf

BIOC201W1 INTRODUCTION TO BIOMOLECULES MS. SR MOKHOSI (Ph.D. Candidate) [email protected] RECOMMENDED BOOKS  1. Principles of Biochemistry. Robert Horton, David Rawn, Gray Scrimgeour, Marc Perry, Laurence A Moran. 4th edition Prentice Hall, 2005, ISBN-13: 9780131453067  2....

BIOC201W1 INTRODUCTION TO BIOMOLECULES MS. SR MOKHOSI (Ph.D. Candidate) [email protected] RECOMMENDED BOOKS  1. Principles of Biochemistry. Robert Horton, David Rawn, Gray Scrimgeour, Marc Perry, Laurence A Moran. 4th edition Prentice Hall, 2005, ISBN-13: 9780131453067  2. Biochemistry. Lubert Stryer. 4th edition W.H. Freeman & Company, 1995, ISBN13: 978-0716720096  3. Lehninger Principles of Biochemistry. David L. Nelson, Michael M. Cox. 4th edition W.H. Freeman & Company, 2000, ISBN-13: 978- 1572599314  4. Biochemistry. Christopher Mathews and K.E. Van Holde. 1st edition BenjaminCummings Pub Co, 1990, ISBN-13: 978-0805350159  MODULE STRUCTURE TOPIC DATE LECTURER LECTURES 1. Carbohydrate (CHO) 13 February - 1 March Ms. SR Mokhosi 12 Chemistry 2. Lipid Chemistry 5 – 28 March Ms. SR Mokhosi 13 3. Amino acids & proteins 8 – 25 April Dr. L Ngobese 12 4. Enzymes, Vitamins & 26 April – 10 May Dr. L Ngobese 9 Cofactors 5. Nucleic acids & protein 13 May– 21 May Dr. L Ngobese 4 synthesis  ASSESSMENT DATES (TBC)  A. MINOR ASSESSMENTS (50%)  1.Theory Assess 1: CHO / Lipid Chemistry (Thursday, 28 March) – Ms Mokhosi (10%)  2.Theory Assess 2: Amino acids/Enzymes… (Thursday, 9 May) – Dr Ngobese (10%)  3. Practical Assess: Practicals 1 to 8… (Thursday, 16 May) – Ms Mokhosi/Dr Ngobese (10%)  *Make-up Assessment Dates: To be announced  ASSESSMENT DATES (TBC) Practical report Submissions (15%) Tutorial Quiz Submissions (5%) CHO Lipid Amino Acid Enzymes, Nucleic acids & Metabolism Metabolism Metabolism Vitamins & protein synthesis Cofactors Tutorial 1 1 1 1 1 Quizzes MAJOR ASSESSMENTS: (50%) Main Exam (3 hours): Date to be advised Supplementary Exam (3 hours): Date to be advised 1. INTRODUCTION TO CARBOHYDRATES What and where do we find Carbohydrates? What sets them apart from other biomolecules? Simple and complex Carbohydrates? What about a ketogenic diet? Could we do away with Carbs? Are all carbohydrates good? WHAT ARE CARBOHYDRATES?  Carbohydrates are essential components of all living organisms viz. humans, plants, animals, bacteria, and viruses.  Carbohydrates contain an aldehyde (-CHO) or ketone (-C=O) group with two or more hydroxyl (-OH) groups in their structures.  Examples include: Glyceraldehyde, Dihydroxyacetone, Glucose, Fructose  General classification: monossacharides, dissacharides, oligossacharides, polyssacharides, based on the numbers of monomeric units present Page 2 in Handouts CARBOHYDRATES - INTRO How many carbons? Can you spot the difference between the adjacent structures? Note: CHOs can be aldose or ketose upon whether aldehyde or ketone group present in their structures  2. MONOSSACHARIDES  Monosaccharides are the basic unit of carbohydrates.  They are water-soluble white crystalline solids with a sweet taste.  Every individual monomeric unit of a carbohydrate is called monosaccharide  Examples include glucose, fructose, galactose, ribose (in RNA), Deoxyribose (in DNA)  They cannot be hydrolyzed into a simpler form of carbohydrates as they are already in simplest form Page 2 in D-Fructose D-Glucose Handouts MONOSSACHARIDES Several classes depending on the number of carbon atoms present in their structures such as- i. Trioses: 3-carbon monosaccharides ii. Tetroses: 4-carbon monosaccharides iii. Pentoses: 5-carbon monosaccharides iv. Hexoses: 6-carbon monosaccharides v. Heptoses: 7-carbon monosaccharides Page 2 in Handouts MONOSSACHARIDES  Ketoses are isomers of aldoses, i.e. same number and kinds of atoms, but different structural or spatial configurations  The isomers of carbohydrates are classified into two different classes, such as- i. Structural isomers ii. Optical isomers or stereo-isomers Page 2 in Handouts  A. STRUCTURAL ISOMERISM IN MONOSSACHARIDES Commonly the difference is seen on Carbons 1 and 2 (no variation in spatial arrangement) i. Erythrose (Aldose) and Erythulose (Ketose) : 4-carbon monossacharide ii. Ribose and Ribulose : 5-carbon monossacharide iii. Xylose and Xylulose: 5-carbon monossacharides Page 3 in Handouts  STRUCTURAL ISOMERISM CONTD. Hexose Sugars – Spot the 8 aldoses and 4 ketoses. Can you identify the 4 structural isomers here? Page 3 in Handouts  PYRANOSE AND FURANOSE RING STRUCTURE  In solution, glucose and fructose do not exist in open-chain structures, Haworth showed that they cyclize into rings, forming hemiacetals and hemiketals  Hexoses form when the second to last –OH group reacts with a C=O  Aldohexoses form 6-membered rings, and ketohexoses and aldopentoses form 5 – membered rings Page 5 in Handouts HAWORTH STRUCTURES Page 5 in Handouts HAWORTH STRUCTURES Page 6 in Handouts HAWORTH VS CHAIR FORMATION STRUCTURE The 6-membered ring is not planar but rather exists in the chair formation Page 6 in Handouts  B. STEREOISOMERS  Same structural formula but with different spatial configuration i) Enantiomers – four different atoms or groups of atoms are attached. All monosaccharides except dihydroxyacetone contain 1 or more asymmetric carbons  The D (dextro) and L(levo) of glyceraldehyde contain a single asymmetric carbon – and are mirror images Page 7 in Handouts ENANTIOMERS: D AND L CONFIGURATIONS Page 7 in Handouts ENANTIOMERS: D AND L CONFIGURATIONS Page 7 in Handouts  EPIMERS  Same structural formula but with different spatial configuration ii) Epimers – isomers that differ due to the H and OH configuration of carbons 2 or 3 or 4 Page 7 in Handouts  DIASTEREOISOMERS  D-Glucose and D-mannose are epimers at C-2, and D-glucose are D-galactose are epimers at C-4  Note: there is no epimeric relationship between D-galactose and D-mannose, their differences are at more than 1 carbon (i.e. 2 and 4); hence they are diastereoisomers – (neither epimers, nor enantiomers)  STEREOISOMERS  Same structural formula but with different spatial configuration A. Anomers ANOMERS  iii. Anomers - Following cyclisation, there is an additional asymmetric carbon added.  The C-1 in a ring structure can become the asymmetric centre of the ring, resulting in the alpha- and beta-configurations of the sugar Page 8 in Handouts ANOMERIC CARBON -HAWORTH STRUCTURES Page 8 in Handouts  OPTICAL ISOMERISM  The presence of the asymmetric carbons or chirality influences the optical activity of compounds  E.g. the D and L enantiomers of glyceraldehyde with identical properties, including boiling, melting points and solubities BUT they differ in optical activity  This relates to how it rotates the plane of polarized light where L rotates clockwise, while D rotates it counter-clockwise  In addition to this, you can have D(+) vs D(-) isomers, e.g. D(+) is natural glucose while natural fructose is D(-)  Please watch this video on optical isomerism: https://www.youtube.com/watch?v=RBtgAz70_JY