Proteoglycans

Question 0

The GAGs in PGs are poly anions or cations?

Answer 0

Anions

Question 1

What are the component parts of a proteoglycan (PG)?

Answer 1

Core protein, repeating disaccharide, glycosaminoglycan (GAG) made of repeats of an amino sugar and an acid sugar

Question 2

PGs withstand pressure well because they are:

Answer 2

Hydrated with water and bound Na+ causing a swelling pressure

Question 3

How is it that Na+ is attracted to GAGs?

Answer 3

GAGs are negatively charged, so they attract +ive charges such as those in Na+

Question 4

PGs are commonly found in what tissues where resistance to compressive forces would be valuable?

Answer 4

Cartilage

Question 5

Aggregates of PGs are called:

Answer 5

Aggrecan

Question 6

________ proteins are the proteins onto which GAG chains are O-glycosidically liked by serine residues to form PGs.

Answer 6

Core proteins

Question 7

Define GAG.

Answer 7

Repeating disaccharide which forms the “glycan” of proteoglycan.

Question 8

PGs are distinguished by their variable:

Answer 8

GAG chains. Although each chains is a pure repeating disaccharide, the repeated disaccharide determines the name.

Question 9

Which GAG exists as a free GAG, not covalently attached to protein like in a proteoglycan, and is not sulfated?

Answer 9

Hyaluronate (hyaluronic acid)

Question 10

Name 4 GAGs that are covalently attached to proteins through serine and a link trisaccharide, and are sulfated.

Answer 10

Chondroitin sulfate, dermatan sulfate, heparin sulfate, heparin.

Question 11

Name three tissues in which hyaluronic acid is found.

Answer 11

Cartilage, Synovial fluid, vitreous humor

Question 12

What is required for link trisaccharides and GAGs to be added to proteins?

Answer 12

(ASP/GLU-X-SER-GLY) forming a serine O-glycosylation recognition sequence.

Question 13

Link trisaccharides usually link _________ to __________

Answer 13

Proteins to GAGs

Question 14

What is the last step in PG synthesis?

Answer 14

Sulfation of the GAG, adding negatively charged sulfate groups that will attract H2O and Na+

Question 15

Name a shock absorbing PG aggregate found in cartilage.

Answer 15

Aggrecan (a hyaluronic acid molecule)

Question 16

Fibroblast Growth Factor can serve to store ________ __________ to make them readily available for healing and repair when needed (such as after a cartilage tear)

Answer 16

Growth factor

Question 17

Cell surface and extracellular matrix _______________ aid interactions of cell surface adhesive proteins like integrin and Fibronectin to provide fine tuning of matrix-cell interactions.

Answer 17

Proteoglycans

Question 18

Because of their capacity for multiple interactions with other proteins, growth factors and cells, __________ can act as an all purpose, reversible glue.

Answer 18

Proteoglycans

Question 19

Describe the process by which PGs are internalized and catabolized.

Answer 19

Core protein is internalized and can be recycled but the GAG chains are degraded.

Question 20

Mucopolysaccharidoses are caused by:

Answer 20

Defects in recycling of PGs and mucolipids from the cell surface.