1Welcome to the CARBOHYRDRATE sectionof BCMB8020Before next class please readClass Text: Chapter 7: pages 356-381 &Chapter 23 pages 852-862(Biochemistry, third Edition by Voet and Voet, 2004, Wiley).Articles by Rudd et al., 2004;Shearer and Graham (2004);James et al., 2003. Please pick up the 5 handoutsToday these articles will be given out in class. All future required reading, as well as optional reading, will be available as pdf files on the website http://cell.ccrc.uga.edu/~dmohnen/bcmb8020/list.html Carbohydrates- General Review•Functions•Introduction and definition monosaccharides•Aldoses and Ketoses•Cyclic glycosyl residues, Haworth Projections•Modified monosaccharides•Glycosidic bond•Disaccharides•Polysaccharides•Peptidoglycans•Proteoglycans•GlycoproteinsCarbohydrates* most abundant organic molecule on earth* polyhydroxy aldehydes or ketones (or yield these upon hydrolysis)* functions: energy storage (glycogen, starch)metabolic intermediates (ATP, coenzymes)part of DNA & RNAstructural elements in cell walls of bacteria,fungi & plantsexoskeleton of arthropodsextracellular matrix of animalscell-cell communication/signallingCarbohydrates- General Review•Introduction and definition monosaccharides•Aldoses and Ketoses•Cyclic glycosyl residues, Haworth Projections•Modified monosaccharides•Glycosidic bond•Disaccharides•Polysaccharides•Peptidoglycans•Proteoglycans•Glycoproteins•Individual monomeric units are calledmonosaccharides (CH20)n where n≥3•oligosaccharides (contain 2-20 monosaccharides)disaccharides (two linked monosaccharides) •polysaccharides (> 20 monosaccharides)• pure mono- & disaccharides are water-soluble,colorless in solution & sweet •two classes of monosaccharides: aldoses & ketoses2Glycoconjugate: carbohydrate derivative where carbohydrate(s) are linked to a peptide, protein or lipid (i.e. proteoglycans, peptidoglycans, glycoproteins, glycolipids)Glycan: carbohydrate polymerSterioisomers: compounds with the same molecular formula but different spatial arrangement of their atomsD & L sugars differ only in steric arrangement of atoms about central C. They are non-superimposable mirror images (i.e. enantiomers)They differ in orientation of the crystals, in directions in which solutions rotate polarized light, and in selectivity of reaction with other asymmetric moleculesFischer projections of: (a) L- and D-glyceraldehyde, (b) dihydroxyacetoneStereo view of L- and D-glyceraldehyde(L) (D) (L) (D) N (# of Cs) Name Example3triose4tetrose5pentose6 hexoseFor sugars with >1 asymmetric (chiral) carbon, D & L refer to chiral C furthest from aldehyde (or ketone) & correspond to D & L glyceraldehyde# of sterioisomers = 2n where n = # of chiral C’sEpimer: sterioisomers that differ in configuration at only one chiral centerCarbohydrates- General Review•Introduction and definition monosaccharides•Aldoses and Ketoses•Cyclic glycosyl residues, Haworth Projections•Modified monosaccharides•Glycosidic bond•Disaccharides•Polysaccharides•Peptidoglycans•Proteoglycans•Glycoproteins3xxxxxxxxxFig. 11-1 Structure of the 3-6 carbon D-aldoses(blue are the most common)You must memorize the structure of all the sugars marked with an asterix!**Fig. 11-1 (aldoses continued)***Fig 11-1 (aldoses continued)****Fig 11-2 Fisher projections of the 3 to 6 carbon D-ketoses (blue structures are most common)xxxxxxxx**Fig. 11-2 (ketoses continued)**Fig 11-2 (ketoses continued)*4Basis for Cyclization of Aldoses and KetosesFig. 11-3 Reaction of an alcohol with:(a) An aldehyde to form a hemiacetal(b) A ketone to form a hemiketal Formation of a hemiacetalFormation of a hemiketalCarbohydrates- General Review•Introduction and definition monosaccharides•Aldoses and Ketoses•Cyclic glycosyl residues, Haworth Projections•Modified monosaccharides•Glycosidic bond•Disaccharides•Polysaccharides•Peptidoglycans•Proteoglycans•Glycoproteins(a) Pyran and (b) Furan ring systems(a) Six-memberedsugar ring is a “pyranose”(b) Five-memberedsugar ring is a “furanose”Fig 11-4 Cyclization of D-glucose to form glycopyranoseFig. 11-4 (cyclization of D-glucose, continued)Haworth Projection• Reaction of C-5 hydroxyl with one side of C-1 gives α, reaction with the other side gives β*** anomeric carbonAldoses where Cn(n ≥ 5) or ketoses (n ≥ 6) yield cyclic hemiacetals (or hemiketals) in solution6 member ring = pyranose5 member ring = furanoseanomeric C = most oxidized C of cyclic monosaccharide. It is chiral (i.e. α or β) = anomeric configuration*** In solution the ring & linear from of monosacchardiesare in equilibrium! Example: D-glucose at 31°C 64% β-D-pyranose36% α-D-pyranose< 1% furanose or linear5Cyclization of D-ribose to form α- and β-D-ribopyranose and α- and β-D-ribofuranoseContinued on next slide(Cyclization of D-ribose continued)Continued next slide(Cyclization of D-ribose continued)31°C at equilibrium21.5%58.5%6.5% 13.5%<1% open chainFigure 11-5 The anomeric monosaccharides α-D-glucopyranose and β-D-glucopyranose, drawn as both Haworth projections and ball-and-stick models.Page 359Conformations of MonosaccharidesFigs. 11-6 & 11-7 Conformations of β-D-ribofuranoseTen possible envelope & ten possible twist conforma-tionsFig 11-6 Conformations of β-D-glucopyranose(b) Stereo view of chair (left), boat (right)Haworth projection Chair conformationBoat conformation2 possible conformations (generally more stable)6 possible conformations*Axial substituent: perpendicular to plane of ring** Equatorial substituent:parallel to planeof ring************6Fig 11-6 Conformations of β-D-glucopyranose• Top conformer is more stable because it has the bulky hydroxyl substituents in equatorialpositions(less steric strain) Carbohydrates- General Review•Introduction and definition monosaccharides•Aldoses and Ketoses•Cyclic glycosyl residues, Haworth Projections•Modified monosaccharides•Glycosidic bond•Disaccharides•Polysaccharides•Peptidoglycans•Proteoglycans•GlycoproteinsDerivatives of Monosaccharides• Many sugar derivatives are found in biological systems• Some are part of monosaccharides, oligosaccharides or polysaccharides• These include sugar phosphates, deoxy and amino sugars, sugar alcohols and acidsYou must know these abbreviations for selected monosaccharides and their derivativesSugar PhosphatesSome important sugar phosphatesDeoxy Sugars• In deoxy sugars an H replaces