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The stereochemical relationships, shown in Fischer projection, among the D -aldoses with three to six carbon atoms.

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Presentation on theme: "The stereochemical relationships, shown in Fischer projection, among the D -aldoses with three to six carbon atoms."— Presentation transcript:

1 The stereochemical relationships, shown in Fischer projection, among the D -aldoses with three to six carbon atoms.

2 The stereochemical relationships among the D -ketoses with three to six carbon atoms.

3 The reactions of alcohols with (a) aldehydes to form hemiacetals and (b) ketones to form hemiketals. These reactions are freely reversible in aqueous solution.

4 Cyclization of hexoses: anomerization

5 The anomeric monosaccharides  - D -glucopyranose and  - D - glucopyranose, drawn as both Haworth projections and ball-and- stick models

6 Conformations of the cyclohexane ring (a) in the boat conformation and (b) in the chair conformation

7 The two idealized chair conformations of  - D -glucopyranose 4C14C1 1C41C4 more stableless stable

8 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

9 The reversible oxidation of L -ascorbic acid to L -dehydroascorbic acid lactones

10 N-Acetyl-neuraminic (sialic) acid in its linear and pyranose forms an  -ketoacid

11 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

12 Common disaccharide: sucrose

13 Common disaccharide:  -lactose

14 Common disaccharide:  -maltose

15 Common disaccharide:  -isomaltose

16 Common disaccharide:  -cellobiose

17 Electron micrograph of the cellulose fibers in the cell wall of the alga, Chaetomorpha melagonium

18 Primary structure of cellulose:......  - D -glucopyranosyl-(1,4)-  - D -glucopyranosyl-......

19 Proposed structural model of cellulose Extensive H-bonding network (intra- and interchain: responsible for the rigidity of cellulose fibers

20 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

21  -Amylose: D -glucose residues are linked by  -(1  4) bonds (red)......  - D -glucopyranosyl-(1,4)-  - D -glucopyranosyl-......

22  -Amylose: this regularly repeating polymer forms a left-handed helix.

23 Amylopectin: Primary structure near one of it’s  (1  6) branch points (red)

24 Amylopectin showing its bushlike (compact, globular) structure (glucose residues at branch points indicated in red) Glycogen is amylopectin-like but with greater branching

25 Photomicrograph showing the glycogen granules (pink) in the cytoplasm of a liver cell

26 N-Linked oligosaccharides: all N-glycosidic protein attachments occur through a N-acetyl-  - D - glucosamine–Asn bond to Asn–X–Ser/Thr

27 N-Linked oligosaccharides: N-linked oligosaccharides usually have the branched (mannose) 3 (NAG) 2 core shown

28 N-Linked oligosaccharides: some examples of N-linked oligosaccharides

29 The microheterogeneous N-linked oligosaccharide of RNase B has the (mannose) 5 (NAG) 2 core shown

30 Some common O-glycosidic attachments of oligosaccharides to glycoproteins (red): blood group antigens (glycophorin)

31 Disaccharide repeating units of the common glycosaminoglycans (proteoglycans): connective tissue; cartilage

32 X-ray fiber structure of Ca 2+ hyaluronate Hyaluronidase: a glycosidase that cleaves the  -(1,4) linkages of hyaluronic acid

33 Proteoglycans: (a) Electron micrograph showing a central strand of hyaluronic acid. (b) Bottlebrush model of the proteoglycan aggrecan.

34 Model of oligosaccharide dynamics in bovine pancreatic ribonuclease B (RNase B)

35 Schematic diagram comparing the cell envelopes of (a) gram- positive bacteria and (b) gram-negative bacteria

36 Chemical structure of peptidoglycan of bacteria: the repeating unit of peptidoglycan

37 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

38 Structure of penicillin: inhibits bacterial cell wall biosynthesis

39 Enzymatic inactivation of penicillin

40 Structure of teichoic acid Other bacterial cell wall antigenic groups

41 Unusual monosaccharides occur in the O-antigens of gram- negative bacteria; are subject to rapid mutational alteration (new bacterial strains)

42 END

43 The surfaces of a normal mouse cell as seen in the electron microscope.

44 The surfaces of a cancerous cell as seen in the electron microscope.

45 Scanning electron micrograph of tissue from the inside of a human cheek.

46 Properties of some proteoglycans


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