Glycoproteins and Glycosylation Mechanisms

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Questions and Answers

What percentage of a glycoprotein's weight is typically comprised of oligosaccharides?

5-10%

20-25%

10-15% (correct)

15-20%

Which amino acid is involved in N-Linked glycosylation?

Threonine

Asparagine (correct)

Serine

Glutamine

In which organelle does O-Linked glycosylation take place?

Golgi apparatus (correct)

Nucleus

Ribosome

Mitochondria

What is the role of dolichol phosphate in N-Linked glycosylation?

It binds activated sugars and enables flipping. Signup and view all the answers

What can result from dysfunction in lysosomal targeting of glycoproteins?

Lysosomal storage diseases Signup and view all the answers

Which of the following structures are glycosaminoglycans (GAGs) primarily known for?

Structural support and lubrication Signup and view all the answers

What type of linkages does O-Linked glycosylation involve?

Hydroxyl groups of serine or threonine Signup and view all the answers

Which of the following best describes the basic structure of glycosaminoglycans (GAGs)?

Long unbranched polysaccharides Signup and view all the answers

What is the primary function of glycoproteins?

Cell signaling and surface interactions Signup and view all the answers

Which amino acid is notably involved in N-Linked glycosylation?

Asparagine Signup and view all the answers

What triggers the endocytosis of glycoproteins into lysosomes?

Cell surface interaction Signup and view all the answers

What role do lysosomal glycosidases play in glycoprotein degradation?

Remove sugars from glycoproteins Signup and view all the answers

Which of the following is a characteristic of glycosaminoglycans?

Long and linear structure Signup and view all the answers

What is a common function of proteoglycans in connective tissue?

Cell adhesion Signup and view all the answers

What is a consequence of lysosomal hydrolase deficiencies?

Lysosomal storage diseases Signup and view all the answers

In Hurler syndrome, what is primarily accumulated in the body due to the disorder?

Excess glycosaminoglycans Signup and view all the answers

Which enzyme deficiency is associated with Inclusion-cell disease (I-cell disease)?

Hydrolytic enzymes Signup and view all the answers

What is the first sugar removed during glycosaminoglycan degradation?

Last moiety added Signup and view all the answers

Which characteristic describes Hyaluronan, a type of glycosaminoglycan?

Contains 25,000 disaccharide units Signup and view all the answers

What effect do lysosomal storage diseases have on the nervous system?

Change in cell signaling Signup and view all the answers

What is the first step in the assembly of glycosaminoglycans on proteins?

Tetrasaccharide added Signup and view all the answers

What is a common symptom of I-cell disease?

Severe developmental delays Signup and view all the answers

Which class of biogenic amines includes compounds like serotonin and tryptamine?

Aromatic and heterocyclic Signup and view all the answers

What is the rate limiting step in catecholamine synthesis?

Tyrosine hydroxylation Signup and view all the answers

Which cofactor is essential for the enzyme tyrosine hydroxylase?

Tetrahydrobiopterin Signup and view all the answers

How are biogenic amines primarily synthesized?

Decarboxylation of amino acids Signup and view all the answers

Which of the following functions is NOT associated with biogenic amines?

Production of enzymes Signup and view all the answers

What role do monoamine oxidases (MAO) play in the body?

Degrade biogenic amines Signup and view all the answers

Which statement about biogenic amines degradation is true?

Amine oxidases are involved in their breakdown. Signup and view all the answers

Which co-substrate is required for the degradation of biogenic amines by monoamine oxidases?

S-adenosyl-L-methionine Signup and view all the answers

What is a common consequence of monoamine oxidase A deficiency?

Build-up of neurotransmitters Signup and view all the answers

Which substance can potentially build up due to vitamin B12 deficiency?

Histamine Signup and view all the answers

What type of biogenic amine is cadaverine classified as?

Aliphatic monoamine Signup and view all the answers

Which biogenic amine is synthesized from tryptophan?

Serotonin Signup and view all the answers

What is the primary role of agmatine as a biogenic amine?

Neurotransmission Signup and view all the answers

Which of the following biogenic amines plays a significant role in the fight or flight response?

Epinephrine Signup and view all the answers

Study Notes

Glycoproteins

Proteins covalently linked to oligosaccharides or polysaccharides
10-15% oligosaccharide in weight by mass

Amino Sugars

Sugar molecules with amino and acetate groups
Example: N-acetylglucosamine (GlcNAc)

N-Linked Glycosylation

GlcNAc is added to the amide nitrogen of an asparagine (Asn) residue
Asn-X-Ser/Thr consensus sequence required where X is any amino acid except proline
Glycosylation occurs within the ER lumen

O-Linked Glycosylation

N-acetylgalactosamine (GalNAc) and other saccharides are addedto the hydroxyl group of serine (Ser) or threonine (Thr) residues
Glycosylation occurs within the Golgi lumen

N-Linked Glycosylation Assembly and Modification

Dolichol phosphate is a lipid carrier that spans the ER membrane
Dolichol phosphate binds to activated sugars
Dolichol phosphate facilitates the "flipping" of sugars across the ER membrane
Oligosaccharyltransferase is a glycosyltransferase that adds sugars to proteins within the ER lumen

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Description

Explore the fascinating world of glycoproteins and their glycosylation processes in this quiz. Test your understanding of N-linked and O-linked glycosylation, including the roles of amino sugars and the cellular mechanisms involved. Ideal for students studying biochemistry and molecular biology.