Carbohydrate Structure Flashcards
carbohydrate formula
alpha-D-glucose
beta-D-glucose
beta-D-galactose
alpha-D-galactose
oligosaccharide
between 2-20 sugar units
polysaccharide
> 20 sugar units
aldose
C=O at end of chain
ketose
C=O in middle of chain
triose
3 carbons (glyceraldehyde)
4 carbons
tetrose (erythrose)
pentose
5 carbons; ribose
hexose
6 carbons; glucose
all monosaccharides are _
chiral, except dihydroxyacetone
enantiomers
non-superimposable mirror images (stereoisomers)
pure enantiomer
rotates polarized light
Fischer projection
horizontal is toward reader; vertical is away
perspective formulas
solid line is toward reader; dash is away from reader
Which carbon is designated D or L?
the chiral carbon most distant from the carbonyl group
a molecule with _ chiral centers can have _ stereoisomers
n, 2^n
epimers
two sugars that differ in stereo configuration at only one carbon position
cyclization
intramolecular attack at anomeric C
mutarotation
interconversion of alpha and beta anomers
6 membered ring
pyranose
5 membered ring
furanose
alpha-D-sugars
OH down
beta-D-sugars
OH up
intermolecular attack results in _
di- or polysaccharide
formation of a ring
reaction between aldehyde at C1 and hydroxyl at C5 results in hemiacetal –> hemiacetal carbon becomes new chiral center (anomeric carbon)
formation of di- or polysaccharide
-OH of glucose molecules condenses with hemiacetal of other glucose molecule –> eliminates H2O –> forms O-glycosidic bond
glycosidic bond
between hemiacetal or hemiketal group of a saccharide and -OH of another saccharide
all monosaccharides are _
reducing sugars
oxidation of anomeric C
CHO to COO-
aldehydes can be oxidized to _
carboxylic acids
maltose
glucose + glucose with alpha-1,4 bond
lactose
glucose + galactose by 1,4-beta bond
reducing disaccharides
lactose and maltose
non-reducing disaccharides
sucrose, trehalose
sucrose
fructose + glucose by beta-2,alpha-1 link
trehalose
glucose + glucose with alpha-1,1 linkage
proteoglycans, glycoproteins
polysaccharides with protein attachment
lipopolysaccharides, glycolipids
polysaccharides attached to lipids
polynucleotides
polysaccharides attached to PO4, N-bases
glycogen and starch
alpha-1,4 linkage with alpha-1,6 branches; soluble and soft
starch polysaccharides
amylose (10-20 percent) and amylopectin (80-90 percent)
cellulose
beta-1,4 linkages with no branching; insoluble
glycogen
readily accessible source of stored fuel in animal cells
glycogen storage
stored in cells of liver and muscles; converted to glucose for energy
Why glycogen instead of glucose?
cells would rupture due to osmosis and if [glucose] was always high, it would be hard for cells to uptake glucose when needed
glycoprotein
carbohydrate and covalently linked protein; mono-, di-, or polysaccharides
proteoglycans
subclass of glycoproteins in which carbohydrates are glycosaminoglycans
GAGs
long linear polysaccharides consisting of repeating disaccharide units; contain negatively charged sulfate and carboxylate groups which can bind lots of water
bound water in GAGs
gives them lubricant or cushioning properties for their role in cartilage, tendons, heart valves, etc.
most important GAGs
hyaluronic acid, dermatan sulfate, chondroitin sulfate, heparin, heparan sulfate, keratan sulfate
b-lactam antibiotics (penicillin)
inhibit formation of peptidoglycan cross-links in bacterial cell wall
gram-positive bacteria
outer layer is peptidoglycan cell wall
gram-negative bacteria
have outer membrane around the cell wall
lectins
proteins that recognize and bind to specific oligosaccharide structures
glucose and galactose are _
epimers
