MCBG - Post-Translational Modification (Secretory Pathway)

Question 1

What sort of secretion is collagen?

Answer 1

Constitutive

Question 2

What sort of secretion is insulin?

Answer 2

Regulated

Question 3

Give some examples of proteins delivered via the constitutive secretory pathway.

Answer 3

Immunoglobulins, albumin, prohormones, collagen, fibronectin, laminin, receptors

Question 4

Give some examples of proteins delivered via the regulated secretory pathway.

Answer 4

Insulin, glucagon, beta-endorphin, ACTH, alpha-MSH, beta-lipotropin, trypsin

Question 5

Where does the word “collagen” come from?

Answer 5

Greek “kolla” meaning glue

Question 6

True or false - collagen is the most abundant protein in the body.

Answer 6

True - 25%-35% of all proteins

Question 7

Which cells produce collagen?

Answer 7

Fibroblasts

Question 8

How many polypeptide chains make up tropocollagen?

Answer 8

3 alpha polypeptide chains, each roughly 1000 aa long

Question 9

True or false - collagen has a glycine in every fourth position along each alpha chain?

Answer 9

False - it’s every third position

Question 10

Give some characteristics of the triple helix structure of collagen.

Answer 10

• non-extensible
• non-compressible
• high tensile strength

Question 11

Why is glycine the only amino acid that could be in the alpha chain in collagen?

Answer 11

Only amino acid with side chain small enough

Question 12

The basic pattern of the alpha chain is this:

(Gly-X-Y)n

What is X usually?

Answer 12

Proline or hydroxyproline, can also be some Y positions

Question 13

What shape is tropocollagen?

Answer 13

300nm rod-shaped

Question 14

How are the alpha chains linked?

Answer 14

H-bonds

Question 15

What does prolyl hydroxylase require to work?

Answer 15

Vitamin C and Fe2+

Question 16

What is the result of having weak tropocollagen triple helices due to insufficient vitamin C?

Answer 16

Scurvy

Question 17

How does prolyl hydroxylase strengthen the triple helices?

Answer 17

Hydroxylates residues, leading to formation of more H-bonds

Question 18

What does lysyl oxidase require to work?

Answer 18

Vitamin B6 and Cu2+ ions

Question 19

What does lysyl oxidase do?

Answer 19

Forms covalent cross-links between tropocollagens.

Question 20

Why is tropocollagen secreted before final processing occurs?

Answer 20

It is too big and would destroy the cell if it were assembled within it

Question 21

Which disorder can arise due to mutation in collagen or lysyl oxidase deficiency?

Answer 21

Ehlers-Danlos Syndrome (EDS)