Roles of the ER and Golgi Complex in Protein Glycosylation

Question 1

what is glycosylation?

Answer 1

addition of carbohydrate side chains to specific amino acid residues of proteins, usually beginning in the lumen of the ER and completed in the Golgi

Question 2

what are the two types of glycosylation?

Answer 2

N-linked glycosylation

O-linked glycosylation

Question 3

describe N-linked glycosylation.

Answer 3

involves the addition of a specific oligosaccharide unit to the nitrogen atom on the terminal amino group of certain asparigine residues

Question 4

describe O-linked glycosylation

Answer 4

addition of an oiligosaccharide to the oxygen atom on the hydroxyl group of certain serine and threonine residues

Question 5

what are the initial steps of N-linked glycosylation?

Answer 5

on the cytosolic side of the ER membrane

later steps take place in the ER lumen

carbohydrate side chains initially have a common core oligosaccharide: two units of N-acetylglucosamine

nine mannose units

three glucose units

Question 6

what are terminal glycosylations?

Answer 6

modification of glycoproteins in the golgi complex involving removal and/or addition of sugars to the carbohydrate side chains formed by the prior core glycosylation in the ER