Presentation on theme: "The stereochemical relationships, shown in Fischer projection, among the D -aldoses with three to six carbon atoms."— Presentation transcript:
The stereochemical relationships, shown in Fischer projection, among the D -aldoses with three to six carbon atoms.
The stereochemical relationships among the D -ketoses with three to six carbon atoms.
The reactions of alcohols with (a) aldehydes to form hemiacetals and (b) ketones to form hemiketals. These reactions are freely reversible in aqueous solution.
Cyclization of hexoses: anomerization
The anomeric monosaccharides - D -glucopyranose and - D - glucopyranose, drawn as both Haworth projections and ball-and- stick models
Conformations of the cyclohexane ring (a) in the boat conformation and (b) in the chair conformation
The two idealized chair conformations of - D -glucopyranose 4C14C1 1C41C4 more stableless stable
D -Glucono- -lactone and D -glucurono- -lactone are, respectively, the lactones of D -gluconic acid and D -glucuronic acid. aldonic aciduronic acid Oxidized Monosaccharide Derivatives
The reversible oxidation of L -ascorbic acid to L -dehydroascorbic acid lactones
N-Acetyl-neuraminic (sialic) acid in its linear and pyranose forms an -ketoacid
The acid-catalyzed condensation of - D -glucopyranose with methanol to form an anomeric pair of methyl D -glucopyranosides (Fischer glycosidation); furanosides also form under these conditions
Common disaccharide: sucrose
Common disaccharide: -lactose
Common disaccharide: -maltose
Common disaccharide: -isomaltose
Common disaccharide: -cellobiose
Electron micrograph of the cellulose fibers in the cell wall of the alga, Chaetomorpha melagonium
Primary structure of cellulose:...... - D -glucopyranosyl-(1,4)- - D -glucopyranosyl-......
Proposed structural model of cellulose Extensive H-bonding network (intra- and interchain: responsible for the rigidity of cellulose fibers
Primary structure of chitin:...... - D -GlcNAc-(1,4)- - D -GlcNAc-...... A structural motif similar to that of cellulose: thus, similar physical properties (structure-function correlations) OO
-Amylose: D -glucose residues are linked by -(1 4) bonds (red)...... - D -glucopyranosyl-(1,4)- - D -glucopyranosyl-......
-Amylose: this regularly repeating polymer forms a left-handed helix.
Amylopectin: Primary structure near one of it’s (1 6) branch points (red)
Amylopectin showing its bushlike (compact, globular) structure (glucose residues at branch points indicated in red) Glycogen is amylopectin-like but with greater branching
Photomicrograph showing the glycogen granules (pink) in the cytoplasm of a liver cell
N-Linked oligosaccharides: all N-glycosidic protein attachments occur through a N-acetyl- - D - glucosamine–Asn bond to Asn–X–Ser/Thr
N-Linked oligosaccharides: N-linked oligosaccharides usually have the branched (mannose) 3 (NAG) 2 core shown
N-Linked oligosaccharides: some examples of N-linked oligosaccharides
The microheterogeneous N-linked oligosaccharide of RNase B has the (mannose) 5 (NAG) 2 core shown
Some common O-glycosidic attachments of oligosaccharides to glycoproteins (red): blood group antigens (glycophorin)
Disaccharide repeating units of the common glycosaminoglycans (proteoglycans): connective tissue; cartilage
X-ray fiber structure of Ca 2+ hyaluronate Hyaluronidase: a glycosidase that cleaves the -(1,4) linkages of hyaluronic acid
Proteoglycans: (a) Electron micrograph showing a central strand of hyaluronic acid. (b) Bottlebrush model of the proteoglycan aggrecan.
Model of oligosaccharide dynamics in bovine pancreatic ribonuclease B (RNase B)
Schematic diagram comparing the cell envelopes of (a) gram- positive bacteria and (b) gram-negative bacteria
Chemical structure of peptidoglycan of bacteria: the repeating unit of peptidoglycan
Chemical structure of peptidoglycan: the S. aureus bacterial cell wall peptidoglycan Note the pentaglycine cross-linkages between the chains Lysozyme: a glycosidase that cleaves the -(1,4) linkages of peptidoglycans
Structure of penicillin: inhibits bacterial cell wall biosynthesis
Enzymatic inactivation of penicillin
Structure of teichoic acid Other bacterial cell wall antigenic groups
Unusual monosaccharides occur in the O-antigens of gram- negative bacteria; are subject to rapid mutational alteration (new bacterial strains)
The surfaces of a normal mouse cell as seen in the electron microscope.
The surfaces of a cancerous cell as seen in the electron microscope.
Scanning electron micrograph of tissue from the inside of a human cheek.