Curtin University Carbohydrates 10.PDF

Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J 10. Carbohydrates CARL MOUSLEY Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Learning Objectives When you complete this lecture you will… Understand the classification and structure of com...

Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J 10. Carbohydrates CARL MOUSLEY Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Learning Objectives When you complete this lecture you will… Understand the classification and structure of common carbohydrates Understand some physical, chemical, and functional properties of carbohydrates Describe some of the roles of carbohydrates Describe oligosaccharides and polysaccharides Describe the digestion of carbohydrates Describe lactose intolerance Use the biochemical knowledge you learned to answer questions and solve problems. Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Carbohydrate General Structure & Roles Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Carbohydrates – general structure ‘Hydrate of carbon’ Cx(H2O)n (where n = 3 to 9) The hierarchy of carbohydrates: Monomers - monosaccharides Cannot be hydrolysed into simpler forms Disaccharides Combination of two monosaccharides Polymers - combination of monomers Oligosaccharides - 2 to 20 monosaccharides Polysaccharides - ≥20 monosaccharides Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Carbohydrates - structure Carbohydrates can be linked together in numerous ways Carbohydrates can have branched structures (α or β link) Proteins and nucleic acids have linear structures Carbohydrates can have ‘direction’ in their chains Non-reducing end to reducing end depending on the presence of hydroxyl group at the anomeric carbon Wide distribution in nature One of the most abundant organic molecules Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Carbohydrate terms Glycan Complex carbohydrates Sugar derivatives Term used to indicate a monosaccharide, oligosaccharide or polysaccharide Oligosaccharides Polysaccharides containing one or more types of monosaccharides Glycoconjugates Phosphoylated sugars e.g. glucose-6-phosphate Amino sugars e.g. β-D N acetylglucosamine (NAG) Nucleotides e.g. ATP, GTP Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Carbohydrates – Glycomics Glycan structures are not coded by the genome Enzymes for glycan synthesis and degradation are encoded by genome Pathways are complex and many different types of glycans can be produced Makes glycans difficult to study Glycomics is the study of all glycomes Glycome is the study of all carbohydrates in a cell Similar to other ‘ome’ disciplines such as genome, proteome, etc. Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Carbohydrates - Roles ‘Everyday in society’ Energy source (what we eat) e.g. glucose Textiles (what we wear) e.g. cellulose Paper (what we read, write, and wrap!) e.g. cellulose Some cellular Functions Energy source (see later) Cell recognition Cell to cell communication Signal transduction Faculty of Health Sciences | Curtin Medical School Inflammation Viral entry Bacteria-host interaction Fertility CRICOS Provider Code 00301J Carbohydrates - Roles Biotechnology Antibiotics Aminoglycosides Neomycin Streptomycin From: http://en.wikipedia.org/wiki/Aminoglycoside Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Glucose and Advanced Glycation End Product (AGE) Glycated haemoglobin and AGE products AGE = advanced glycated end products (a damaging role of excess glucose) Excess glucose + protein Excess glucose + haemoglobin Usually occurs without an enzyme Advanced Glycation End Products (AGE) Glycated haemoglobin (GHB) Effects protein structure and function e.g. cross linking proteins HbA1c a diagnostic indicator of the control of Diabetes Cell and tissue damage Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Carbohydrate Roles Important energy and information molecules Hexoses (monosaccharides with six carbons) Fuel/energy Structure Pentoses (monosaccharides with five carbons) Information molecules Energy molecules ATP, GTP Coenzymes Polynucleotides: DNA, RNA NADH Hexoses and pentoses can be interconverted by pentose phosphate pathway in many cells Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Types of Carbohydrates and their Structure Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Basic Carbohydrate types Aldoses Aldehyde group in the structure Ketoses Ketone group in the structure Sugars that contain a free aldehyde or ketone group can reduce (add electrons) cupric ions (Cu 2+) to produce cuprous ions (Cu+). These sugars and are called ‘reducing sugars’. This reaction is used in Benedict’s reagent to detect carbohydrates Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Aldoses Three carbons: triose (aldotriose) Four carbons: tetrose (aldotetrose) Five carbons: pentose (aldopentose) Six carbons: hexose (aldohexose) Epimers - sugars that differ in the configuration at only a single asymmetric carbon. Example, at C4 in D-glucose and Dgalactose. At C2 in D-glucose and D-Mannose Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Aldoses and Epimers Epimers - molecules that differ from one another in configuration at a single chiral centre (diasteriomers) Other examples At C2: D-glucose & D-mannose At C3: D-glucose & D-allose Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Ketoses Ketotriose Ketotetrose Ketopentose Ketohexose Nelson & Cox (2008) Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Carbohydrates: Open and ring form Essentials of Glycobiology Second Edition Chapter 1, Figure 2 Faculty of Health Sciences | Curtin Medical School 3D structural formula (database structure) CRICOS Provider Code 00301J Carbohydrates types Glucose forms pyranose ring structures Fructose forms furanose ring structures Faculty of Health Sciences | Curtin Medical School = = CRICOS Provider Code 00301J Carbohydrates types α and β forms represent distinct anomeric forms of a carbohydrate α form: OH group is down β form: OH group is up Faculty of Health Sciences | Curtin Medical School = = CRICOS Provider Code 00301J Carbohydrates types Open chair Chair ANOMERIC CARBON: The carbon derived from the carbonyl carbon compound (C=O) of the open chair form of the molecule Anomeric carbon is always next to the oxygen atom in pyranose/furanose ring and opposite the carbon bound to the acyclic CH2OH group Faculty of Health Sciences | Curtin Medical School CRICOS Provider Code 00301J Carbohydrate mutarotation Anomers are in equilibrium and interconvert between the 2 forms (via the open ring structure) Ring opening followed by bond rotation and ring closure +H2O +H2O 36% Faculty of Health Sciences | Curtin Medical School