Organic Components

Question 1

carbohydrates may be added to protein to make glycoproteins (post-translational modification). The sugar can be O-linked or N-linked.
What is the difference between O and N-linked sugars.

Answer 1

O-linked= sugar added to SERINE or THREONINE residues within mucin polypeptide.

N-linked= sugar added to AMIDE NITROGEN of ASPARAGINE within mucin polypeptide when in the consensus sequence: Asp- other aa-threonine/ serine

Question 2

are o-linked or n-linked sugars found in saliva

Answer 2

both BUT o-linked glycoproteins are more abundant

Question 3

all N-linked sugars have a common cor structure. what is this

Answer 3

3 mannose, attached to 2 GlcNAc(N-acetyl-glucosamine), attached to asparagine, further sugars attached to this

Question 4

another word for sialic acid

Answer 4

N-acetyl-nueuraminate

Question 5

an abundant glycoprotein found in saliva are mucins. what is the structure of a mucin monomer

Answer 5

carboxyl and amino terminal are rich in CYSTEINE residues, can form cross-links via sulphide side chains
in centre, there is 10-80 aa repeat sequence. high in serine and threonine aa therefore saturated with o-linked sugars.