+ BIOL1031 - structural carbohydrate Flashcards
D-glucose
open chain form - chiral
enantiomers of D-glucose
D (made in nature)
L (made in labs)
in cyclic
alpha D-glucopyranose - OH on C1 - down position
beta D-glucopyranose - OH on C1 - up position
glycans
O-glycosidic linkages of monosaccharides polysaccharide - structural carbohydrate
example of disaccharide
maltose - glucose + galactose
a-D-glucopyranosyl(1-4) b-D-glucopyranosyl
cellulose
linear D-glucose (1-4)
from microfibrils and provide structural integrity
hemicellulose
b 1-4 polymer (D-xylopyranose) + side chain - carbohydrate polymer
branched - 500-3000
pectin
mixture of branched polysaccharides
a-(1-4) linked is D-galacturonic acid
agarose
D-galactose linked b (1-4) + glucose = ether bridge (C3 and C6)
very complex polysaccharides - lots of substitution
chitin
N-acetyl glucosamine b (1-4) linked
chitin - found
exoskeleton (insect)
crabs etc
glycosaminoglycans
chondroitin-4-sulphate
keratan-4-sulphate
hyaluronan
glycosaminoglycans - contain
has glucuronic acid with N-acetyl galactosamine/glucosamine with 1-4 and 1-3 linkage
proteoglycan
hyaluronan backbone - monomer contain keratin sulphate and chondroitin sulphate
acetyl glucosamine
glucose + acetyl amino group at C2
carbohydrate polymer
e.g. xylose, galactose etc
bacteria - peptidoglycan
polysaccharide-peptide complex
gram +ve and gram -ve
alternate NAG and NAM linked by tetrapeptides
gram +ve
stops osmotic stress
retain of dye iodine complex - trans dye
gram -ve
thin, single layered between membrane
peptidoglycan tetrapeptide
connected by penta-glycine inter bridge in gram +ve and -ve
NAG
N-acetyl glucosamine
NAM
N-acetyl muramic acid
glycosylation
attachment of oligosaccharide (sugar) to proteins most pass through ER and Golgi (secretory pathway) = glycoprotein
2 types of glycosylation
N-linked
O-linked
N-linked in ER and modified in Golgi
by enzyme - oligosacchoryl transferase
during protein translation
attach to N-acetylglucosamine using asparagine
dolichol
lipid ER membrane holding precursor oligosaccharide
N-linked types
N-acetylglucosamine +NH2 of asparagine
extensively modified in Golgi = complex structure
O-linked
oligosaccharide formed in Golgi
very simple structure linked to Ser, Thr of hydroxyproline
function of glycosylation of protein
protein folding in ER
direct protein
protein function
protein folding in ER
chaperones bond oligosaccharide of partially folded protein
direct protein
lectin guide ER to Golgi and protein sorting on trans Golgi
protein function
improve stability, solubility
oligosaccharide on cell surface interact with lectin - signalling
attachment of FA and lipids example
GPI anchor - help binding to luminal/extracellular surface membrane
GPI
glycosylphosphatidylinositol with terminal carboxyl
lectin
carbohydrate protein cell-to-cell adhesion roles
chaperone in protein folding in ER
calnexin and calreticulin
