Glycoproteins

Question 0

Where are glycoproteins located?

Answer 0

Anchored to the extra cellular surface by lipid ceremide or a protein

Question 1

Five locations of glycoproteins

Answer 1

Cell surface receptors 
Blood group determinants
Collagen 
Fibronectin
Protective barrier

Question 2

What is unique about the structure of mucins?

Answer 2

Negatively charged sialic acid (NANA)

Question 3

What is the function of mucins?

Answer 3

Occupy large space trap water act as protective barrier

Question 4

What is unique about the structure of the oligosaccharide part of glycoproteins?

Answer 4

Mix of d-hexoses, NANA, and L-fucose (C6 has a methyl group)

Question 5

What attaches the oligosaccharide to the protein?

Answer 5

Either an N-glycosidic link (through the amide group of asparagine) or o-glycosidic (OH group of Ser or Thr)

Question 6

O linked oligosaccharides in glycophorin are linked to ser and thr by what?

Answer 6

linking protein is GalNAc (N-acetylgalactosine)

Question 7

What is the characteristic disaccharide attached to hydroxylysine?

Answer 7

Glucose galactose

Question 8

What are the two broad types of N-linked oligosaccharides

Answer 8

Complex oligosaccharides (GlcNAc, L-fucose, NANA)
High mannose oligosaccharides (man)

Question 9

What is the common structure in mammalian N linked oligosaccharides?

Answer 9

Linked to the amide nitrogen of Asn

         Fuc                            Man
            |                            / Asn--GlcNAC--GlcNAc--Man
                                        \
                                          Man

Question 10

Where is the origin of the amine in UDP-Glucosamine?

Answer 10

Glutamine!

Question 11

What is the final step?

Answer 11

CMP-NANA

Question 12

What is the significance of NANA in the synthesis of glycoproteins?

Answer 12

When NANA is present oligosaccharide has a negative charge

Question 13

Where does synthesis of o linked glycosides occur?

Answer 13

Protein made in rER and Glycosylated in golgi. Sugar added one at a time.

Question 14

How does GLycosylation begin?

Answer 14

Transfer of GalNAc onto ser or thr OH group

Question 15

How does synthesis of N-linked glycosides differ from O-linked?

Answer 15

Chain made separately in ER and attached to protein (instead of being added one at a time at Golgi)
Dolichol and dolichol phosphate are necessary!

Question 16

What is the first step in biosynthesis of n-linked glycosides?

Answer 16

Protein synth in rER and enters lumen!

Question 17

What is the second step of N-linked glycosides?

Answer 17

Lipid linked oligosaccharide made with dolichol attached through a pyro phosphate linkage to an oligosaccharide with GlcNAc mannose and glucose

Question 18

What is the third step of N-linked glycoside biosynthesis?

Answer 18

Sugars added to dolichol by Membrane bound glycosyltransferases

Question 19

What is the fourth step of N linked glycoside biosynthesis?

Answer 19

Oligosaccharide transferred to protein by protein oligosaccharide transferase (in ER)

Question 20

5th step in n-linked glycoside biosynthesis?

Answer 20

Removal of specific mannosyl and glucosyl residues as glycoproteins moves through ER

Question 21

6th step In biosynthesis of N-linked glycosides?

Answer 21

Completed in Golgi as either complex or high mannose

Question 22

7th step of biosynthesis of N-linked glycosides?

Answer 22

Final processing

Question 23

What is the inability to degrade GAGs or glycoproteins known as?

Answer 23

Mucoploysaccharidosis!

Question 24

What is the inability to degrade sphingolipids known as?

Answer 24

Sphingolipidosis?

Question 25

What targets n-linked glycoproteins for lysosomes?

Answer 25

Mannose 6 phosphate

Question 26

What deficit is there in I cell disease?

Answer 26

Lack the ability to phosphorylate mannose residues

Lysosomal enzymes found in plasma (secreted instead of targeted)