Glycobiology Flashcards
what is glycobiology?
the study of structure, function and biology of carbohydrates also called glycans.
What is the basic structual unit of glycans?
Monosaccharides
what is the difference between an aldose and ketose sugar?
aldose is a monosaccharide that has an adlehyde group and ketose has a ketone.
what carbons can the anomeric centres for the monosacchride ring be found on aldo and keto sugars?
C1 for aldose and C2 for ketose.
How are monosacchrides typically joined?
by glycosidic linkage of hydroxyl groups at the anomeric centre.
What is a glycosphingolipid?
lipids with a carbohydrate attached by glycosidic bond.
Why are glycans known as secondary gene products?
they are not encoded for directly in the genome
what are intrinsic functions performed by glycans?
provide structural components - cell walls, extracellular matrix.
modifying protein properties- solubility, stability
what are the extrinsic functions resulting from glycan-lectin interactions?
Directing trafficking of glycoconjugates intraceullular and extracellularly.
mediating and modulating cell adhesion of cell- cell and cell-matrix interactions.
mediating an modulating signalling intracellular and extracellularly.
What can occur due to the incorrect linkage of glycans?
Anaphylaxis.
what do exoglycosidases and endoglycosidases do?
degrade the glycans by cleaving the sugar chains at the outer terminal end or internally.
What are the stages of N linked glycan attachement?
1) synthesis of lipid linked precursor oligosaccharide
2) en bloc transfer to protein
3) processing - trimming of sugar resides, modification of branch structure, addition of terminal sugar residues
4) secreted from the golgi and then delivered to the plasma membrane.
what is UGGT?
part of the Endoplasmic reticulums quality control system for glycoprotien folding. increases the poitental for correctly folded glycoprotiens.
What do viruses use glycosylation for?
to hide from the immune system.
What simple exteriments can show if a protein is glycosylated?
Use baterial enzyme peptide N-glycosidase F that cleaves most N linked glycans from attached asparagine.
analyse with SDS PAGE to show if protein has glycans or not.
In stage 1 of N glycan biosynthesis what is the name of the lipid that the glycan gets assembled on found on the membrane?
Dolichol phosphate
What is a mucin domain?
Area where there is heavy O linked glycosylation
what is used to analyse the whole glycome?
Ultra high performance liquid chromatography
What are the steps in UPLC?
1) run proteins on SDS gel
2) take the band that corresponds to protein that want to analyse and put into an epindorth (mini test tube thing)
3) add PNGaseF to cut the glycans from protein releasing them into solution
4) add florescence label (procainamide) that binds to the reducing end of the glycan
5) Run on the UPLC.
what is the bond that forms between monosacirides?
glycosidic linkage
what are the steps involved in the synthesis of the oligosacciride precurosor?
Starts in cytoplasm where the glycan is assembled on a lipid called dolichol phosphate. has 2GlcNAc added. then 5 manose added.
then it gets flipped into the ER lumen where a further 4 manoses are added.
