Welcome to the CARBOHYRDRATE section of BCMB8020 Please pick up the 5 handouts Before next class please read Class 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 Today 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 Glycoproteins Carbohydrates 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 RNA structural elements in cell walls of bacteria fungi plants exoskeleton of arthropods extracellular matrix of animals cell cell communication signalling Carbohydrates General Review Introduction and definition monosaccharides Aldoses and Ketoses Cyclic glycosyl residues Haworth Projections Modified monosaccharides Individual monomeric units are called monosaccharides CH20 n where n 3 oligosaccharides contain 2 20 monosaccharides disaccharides two linked monosaccharides Glycosidic bond polysaccharides 20 monosaccharides Disaccharides pure mono disaccharides are water soluble colorless in solution sweet Polysaccharides Peptidoglycans Proteoglycans two classes of monosaccharides aldoses ketoses Glycoproteins 1 Glycoconjugate carbohydrate derivative where carbohydrate s are linked to a peptide protein or lipid i e proteoglycans peptidoglycans glycoproteins glycolipids Glycan carbohydrate polymer Sterioisomers compounds with the same molecular formula but different spatial arrangement of their atoms D L sugars differ only in steric arrangement of atoms about central C They are nonsuperimposable 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 molecules Fischer projections of a L and Dglyceraldehyde b dihydroxyacetone Stereo view of L and D glyceraldehyde L N of Cs 3 4 5 6 Name triose tetrose pentose hexose Example D L D Carbohydrates General Review Introduction and definition monosaccharides Aldoses and Ketoses Cyclic glycosyl residues Haworth Projections Modified monosaccharides For 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 s Glycosidic bond Disaccharides Polysaccharides Peptidoglycans Epimer sterioisomers that differ in configuration at only one chiral center Proteoglycans Glycoproteins 2 Fig 11 1 Structure of the 3 6 carbon D aldoses blue are the most common Fig 11 1 aldoses continued You must memorize the structure of all the sugars marked with an asterix xxxxxxxxx Fig 11 2 Fisher projections of the 3 to 6 carbon D ketoses blue structures are most common Fig 11 1 aldoses continued xxxxxxxx Fig 11 2 ketoses continued Fig 11 2 ketoses continued 3 Basis for Cyclization of Aldoses and Ketoses Formation of a hemiacetal Carbohydrates General Review Introduction and definition monosaccharides Fig 11 3 Reaction of an alcohol with Aldoses and Ketoses a An aldehyde to form a hemiacetal Modified monosaccharides b A ketone to form a hemiketal Cyclic glycosyl residues Haworth Projections Glycosidic bond Formation of a hemiketal Disaccharides Polysaccharides Peptidoglycans Proteoglycans Glycoproteins Fig 11 4 Cyclization of D glucose to form glycopyranose a Pyran and b Furan ring systems a Six membered sugar ring is a pyranose b Five membered sugar ring is a furanose Fig 11 4 cyclization of D glucose continued Haworth Projection Aldoses where Cn n 5 or ketoses n 6 yield cyclic hemiacetals or hemiketals in solution 6 member ring pyranose Reaction of C5 hydroxyl with one side of C 1 gives reaction with the other side gives 5 member ring furanose anomeric C most oxidized C of cyclic monosaccharide It is chiral i e or anomeric configuration anomeric carbon In solution the ring linear from of monosacchardies are in equilibrium Example D glucose at 31 C 64 D pyranose 36 D pyranose 1 furanose or linear 4 Cyclization of D ribose to form and D ribopyranose and and D ribofuranose Cyclization of D ribose continued Continued next slide Continued on next slide Figure 11 5 The anomeric monosaccharides Dglucopyranose and D glucopyranose drawn as both Haworth projections and ball and stick models 58 5 21 5 31 C at equilibrium 6 5 13 5 Page 359 Cyclization of D ribose continued 1 open chain Conformations of Monosaccharides Figs 11 6 11 7 Conformations of D ribofuranose Fig 11 6 Conformations of D glucopyranose Axial substituent perpendicular to plane of ring 2 possible conformations generally more stable Ten possible envelope ten possible twist conformations Equatorial substituent parallel to plane of ring Haworth projection 6 possible conformations Chair conformation Boat conformation b Stereo view of chair left boat right 5 Fig 11 6 Conformations of D glucopyranose Carbohydrates General Review Introduction and definition monosaccharides Top conformer is more stable because it has the bulky hydroxyl substituents in equatorial positions less steric strain Aldoses and Ketoses Cyclic glycosyl residues Haworth Projections Modified monosaccharides Glycosidic bond Disaccharides Polysaccharides Peptidoglycans Proteoglycans Glycoproteins Derivatives 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 acids Sugar Phosphates Some important sugar phosphates You must know these abbreviations for selected monosaccharid es and their derivatives Deoxy Sugars In deoxy sugars an H replaces an OH Deoxy sugars 6 Amino Sugars Fig 11 16 Several amino sugars Amino and acetylamino groups are shown in red An amino group replaces a monosaccharide OH Amino group is sometimes acetylated Amino sugars of glucose and galactose occur commonly in glycoconjugates Sialic acids e g neuraminic acid are important in animal glycoproteins formed from ManNAc pyruvate Sugar Alcohols