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44 Cards in this Set

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Monosaccharides
-building blocks of polysaccharides
-aldehyde or ketone derivatives of straight chain polyhydroxyalcohols (aldose or ketose)
-differ in number of carbon atoms and in arrangement of H and O atoms attached to carbons
Simplest monosaccharides:
contain 3 carbons and are called trioses; the aldehyde triose is called glyceraldehyde and the ketone triose is called dihydroxyacetone
Monosaccharides form polysaccharides by which bonds?
glycosidic bonds
Carbohydrate functions
-source of energy; glucose is the primary fuel (starch in plants and glycogen in animals)
-structural components (cellulose, chitin, peptidoglycan)
-mediate recognition events (oligosaccharides on cell surfaces)
-protective functions (biofilms on bacteria; hylauronic acid --> glycosaminoglycan)
The most abundant sugars in nature are composed of how many carbons?
five and six membered rings
Aldoses are ______ sugars because:
aldoses are reducing sugars because they have a free aldehydic group; some ketoses can also be reducing sugars because they can isomerize to aldoses
Oxidation of the Carbonyl Group in Monosaccharides:
one of the OH groups can be oxidized to a carbonyl group via Tollens Reagent, Ag(NH3)2, which is an oxidizing agent
Oxidation of an aldose produces a:
lactone
Sugar Alcohols:
produced by the reduction of the carbonyl group; also called alditols; not full sugars b/c they are missing C=O; two examples are the sweeteners, xylitol and sorbitol
Reduction of a hydroxyl group on a sugar results in:
a deoxy sugar; one example is fucose, where the CH2OH was reduced to a CH3
Esterification of Monosaccharides produces:
sugar esters; many of these reactions take place between sugar and ATP, where one of the H off the OH is replaced with a phosphate group, forming a negatively charged sugar
T/F: glycosidic bonds can be hydrolyzed back to the alcohols
true
What happens to anomeric carbon in during formation of polysaccharides?
a new chiral carbon is created
How do linear monosaccharides form cyclic structures?
the OH on the second to last carbon (next to the terminal CH2OH)attacks the carbonyl carbon; 5 or 6 membered rings will form preferentially; either the alpha or beta anomer will form
Difference b/w alpha and beta anomers?
alpha: OH on anomeric carbon is pointing down
beta: OH on anomeric carbon is pointing up
Uronic Acids:
have a COOH instead of a CH2OH, which can ionize to become negative
Amino Sugars:
an amino group is substituted for one of the OH on the sugars
Two components of bacterial cell walls:
N Acetyl-B-D-glucosamine
N Acetylmuramic acid
Oligosaccharides are made up of between ___ to ___ sugars.
A polysaccharides is made up of at least ___ sugars.
Oligosaccharides are made of 2-20 sugars; polysaccharides are made up of at least 20 sugars
Homopolysaccharide:
Heteropolysaccharide:
-polysacc made of one sugar
-polysacc made of of 2+ sugar
Cellulose:
-structural polysaccharide
-plant cell walls
-homopolysaccharide (glucose)
-Beta (1--4) linkages
Chitin:
-structural polysaccharide
-insect exoskeleton
-homopolysaccharide (GlcNAc)
-Beta (1--4) linkages
-similar to cellulose
Chitosan:
chemically deacelyated chitin that is more soluable and used for drug delivery
Starch:
-storage polysaccharide
-heteropolysaccharide (alpha-amylose & amylopectin)
*alpha-Amylose
*amylopectin
*linear chain; alpha(1--4) linkages
*branched polysaccharide (24-30 residues); alpha(1--4) and alpha(1--6)
alpha-Amylase:
beta-Amylase:
Debranching Enzymes:
endoglycosidase
exoglycosidase
cut branch points
Glycogen:
-storage polysaccharide
-similar to amylopectin except is more highly branched
-found in liver, skeletal muscle; NOT found in heart/brain
-contains glycogenin protein at heart of every molecule
-linear chains; alpha (1--4)
-branches; alpha(1--6)
Glycosaminoglycans:
linear unbranched chains of repeating disaccharide units; one sugar is N-acetylhexosamine and other is uronic acid; one or both sugars can be sulfated
-adopt highly extended helical conformations
-high density of negative charges attract cations/water
Proteoglycans:
-85-95% carb by weight
-glycosaminoglycan usually found covalently attached to protein
-glycosidic linkage w/ Ser OH
-found in extracellular matrix organization
-"Aggrecan" = cartilage proteoglycan
-"Heparin/HS" bind antithrombin III
Hyaluronic acid = viscous
Peptidoglycan:
-bacterial cell walls
-polysacc of alternating NAM and NAG residues
-tetrapeptide linked to NAM via lactate moiety
-peptidoglycan chains are parallel and covalently cross linked through peptide side chains
Penicillin:
-affects peptidoglycan synthesis
-inhibitor of transpeptidase that cross links peptidoglycan strands
-results in cell lysis
-contains thiazolidine ring fused to B-lactam ring
Penicillinase:
cleaves amide bond of B-lactam ring
Glycoproteins:
-protein with little bit of carbohydrate
-synthesized via glycosyltransferases
N-linked Glycoproteins:
-glycosylation occurs cotranslationally, during protein synthesis in ER
-oligosaccharide is linked to asparagine side chain via amide linkage
-diff types depending on ER/Golgi processing
-High mannose and GlcNAc
O-linked Glycoproteins:
-glycosylation occurs post translationally
-oligosaccharide linked to OH of Ser/Thr via glycosidic bond
N v O linked:
-amide v glycosidic
-co v post translationally
-asp v ser/thr
Oligosaccharide Effect on Protein 3D Conformation:
-stiffens peptide backbone
-limits conformational freedom of polypeptide chain
-stabilize folded conformation
Oligosaccharide Effect on Protein Solubility and Stability:
shields protein from proteases
Oligosaccharide Effect on Protein Localization:
-recognition process aid in taking protein to designated location
examples: M6Phosphate-M6 Phosphate Receptor; Asialoglycoprotein receptor
Oligosaccharide Effect on Protein Function:
glycoprotein hormones: FH, LSH, TSH, hCG; tissue plasminogen activator
Lectins:
proteins that recognize carbohydrates
Examples of Protein/Carb Interactions:
viral infection
fertilization
cell adhesion, differentiation and growth
Selectins:
-glycoproteins that recognize specific carb structures
-mediate binding b/w leukocytes and endothelial cells
-3 types: P, E, L
-sialyl Lewis epitope recognized by selectins
Biomosiamose
-inhibits selectin by mimicking the structure of the sialyl Lewis; contains a mannose instead of fucose ring