Glycobiology

Question 1

what is glycobiology?

Answer 1

the study of structure, function and biology of carbohydrates also called glycans.

Question 2

What is the basic structual unit of glycans?

Answer 2

Monosaccharides

Question 3

what is the difference between an aldose and ketose sugar?

Answer 3

aldose is a monosaccharide that has an adlehyde group and ketose has a ketone.

Question 4

what carbons can the anomeric centres for the monosacchride ring be found on aldo and keto sugars?

Answer 4

C1 for aldose and C2 for ketose.

Question 5

How are monosacchrides typically joined?

Answer 5

by glycosidic linkage of hydroxyl groups at the anomeric centre.

Question 6

What is a glycosphingolipid?

Answer 6

lipids with a carbohydrate attached by glycosidic bond.

Question 7

Why are glycans known as secondary gene products?

Answer 7

they are not encoded for directly in the genome

Question 8

what are intrinsic functions performed by glycans?

Answer 8

provide structural components - cell walls, extracellular matrix.

modifying protein properties- solubility, stability

Question 9

what are the extrinsic functions resulting from glycan-lectin interactions?

Answer 9

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.

Question 10

What can occur due to the incorrect linkage of glycans?

Answer 10

Anaphylaxis.

Question 11

what do exoglycosidases and endoglycosidases do?

Answer 11

degrade the glycans by cleaving the sugar chains at the outer terminal end or internally.

Question 12

What are the stages of N linked glycan attachement?

Answer 12

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.

Question 13

what is UGGT?

Answer 13

part of the Endoplasmic reticulums quality control system for glycoprotien folding. increases the poitental for correctly folded glycoprotiens.

Question 14

What do viruses use glycosylation for?

Answer 14

to hide from the immune system.

Question 15

What simple exteriments can show if a protein is glycosylated?

Answer 15

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.

Question 16

In stage 1 of N glycan biosynthesis what is the name of the lipid that the glycan gets assembled on found on the membrane?

Answer 16

Dolichol phosphate

Question 17

What is a mucin domain?

Answer 17

Area where there is heavy O linked glycosylation

Question 18

what is used to analyse the whole glycome?

Answer 18

Ultra high performance liquid chromatography

Question 19

What are the steps in UPLC?

Answer 19

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.

Question 20

what is the bond that forms between monosacirides?

Answer 20

glycosidic linkage

Question 21

what are the steps involved in the synthesis of the oligosacciride precurosor?

Answer 21

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.