Sugars and Polysaccharides Chapter 8 Lecture 9 1

Saccharide Classification 2 Emperical Formula: C m (H 2 O) n The generic name indicates aldo- or keto- origin, carbon chain length and –ose Common name for a carbohydrate in biochemistry How many chiral carbons are in a 3 carbon aldose (Glyceraldehyde) How about a 3 carbon ketose (dihydroxyacetone) How many stereoisomers are possible in each case? 2 n

Saccharide Classification 3 Fisher Projections show linear form of a sugar According to the Fisher Convention, D or L is determined by stereocenter farthest away from carbonyl L  OH points left GlucoseFructose Glucose and fructose are isomers. Are they tautomers?

Aldoses 4 Epimers – If only One sterocenter changes.

Ketoses 5 Ketone at C2 is most common form

Saccharide Background 6 It is commonly more useful to visualize sugars as cyclic molecules Cyclization occurs through the formation of hemiacetals or hemiketals (Alcohols react with aldehydes or ketones to form hemiacetals or hemiketals)

Saccharide Background 7 We most commonly see 5 (furanose) and 6 (pyranose) member rings hexoketosepentoaldose hexoaldose Will these be furanose or pyranose?

Anomers 8 Anomeric Carbon

Sugars are NOT planar 9 Glucose Which form will be the most stable for glucose epimers? Mannose = C2 Gulose = C3 Galactose = C4

Anomeric Carbon 10 The carbon in position 1 can exist in two different forms:  and . “It’s always better to  e up”

Glycosidic Bonds 11 Polymerization of saccharides occurs through glycosidic bonds 

Saccharide Background 12 Modest differences in glycosidic linkage can have profound influences Starch – fuel source for humans Cellulose – not useful for humans

Reducing Sugars 13 Aldehyde groups can reduce mild oxidizing agents: Tollen’s Test

Modified Sugars 14 Deoxy sugars Amine Substituted for OH Other OH Substitutions

Oxidized Sugars 15 Aldehyde  Carboxylic Acid Aldonic Acid (aldose root name + onic acid) Uronic Acid (aldose root name + uronic acid) Primary Alcohol  Carboxylic Acid

Sugar Modifications 16 Vitamin C (Ascorbic Acid): L-sugar C2 epimer of glucose C2-C3 double bond Oxidized C1 Cyclic form is a furanose Important constituent of glycolipids and glycoproteins (this is the N of H1N1 fame) It’s derivatives are commonly called Sialic Acids

Common Disaccharides 17

Starch 18 Building Block - amylose But NOT a just a 2D chain

Other cool sugars 19 Commonly used for osteoarthritis treatment Important component in synovial fluid

Cellular Enclosure 20 All organisms have a cell membrane – primary component of protection All bacteria and plants have cell walls Some bacteria have an Outer Membrane These organisms have smaller cell walls and periplasmic spaces

Cellular Enclosure 21

Bacterial Cell Wall 22 The bacterial cell wall is a peptidoglycan Building Block:  -N-acetylmuramic acid-(1,4)-N-acetylglucosamine (  -NAM-(1,4)-NAG)

Bacterial Cell Wall 23 In E. coli : Peptide  alanine – diaminopimelic acid - glutamic acid - alanine Covalent crosslink between NAM-NAG polymers DAP

Plant Cell Wall 24 In plants: NO peptide! Building block is cellulose

Plant Cell Wall 25 In plants: NO peptide! Building block is cellulose Network of H-bonds stabilize the 3D structure

Plant Cell Wall 26 Cellulose polymers collapse into cellulose mibrofibrils which interact to form cellulose fibers

Plant Cell Wall 27 Pectin is used to ‘glue’ together the cellulose fibers Substrate of pectate lyase

Glycoproteins 28 N-Linked – Vast majority have NAG  -linked to amide N of Asn O-Linked – Most common is  - galactosyl-(1-3)-  -NAG-Ser/Thr Glycoproteins tend to be secreted. Don’t participate in protein structure

Glycoproteins 29 Glycosyl transferases: enzymes that add sugars Present in the Golgi Glycosidases (glycosyl hydrolases) Remove monosaccharide units

ABO Blood System 30

ABO Blood System 31

ABO Blood System 32