ECM

Question 1

define the ECM

Answer 1

a complex network of secreted macromolecules in the extracellular space

Question 2

The 4 categories of substances found in the ECM are

Answer 2

• organic fibrillar matter
• organic non-fibrillar matter
• ions
• water

Question 3

organic fibrillar matter means

Answer 3

elastin, fibrillin, laminin, fibril-forming collagens

Question 4

organic non-fibrillar matter means

Answer 4

fibronectin, proteoglycans, and lattice forming collagens

Question 5

ions in the ECM are bound to

Answer 5

negatively charged GAG

Question 6

ECM macromolecules are synthesized by

Answer 6

cells of mesenchymal origin such as: fibroblasts, sm cells, chondroblasts, osteoblasts, epithelial cells

Question 7

fibronectin and laminin are

Answer 7

structural glycoproteins

Question 8

collagens account for x% of total protein mass

Answer 8

30%

Question 9

functions of the ECM

Answer 9

• provide support and anchoring for cells
• regulates polarity, differentiation, adhesion, migration, proliferation
• acts as organiser for tissue growth, regeneration, maintenance of tissue structure
• provides for inter-cellular exchange of metabolites, ion, water

Question 10

the amount of ECM is a constant?

Answer 10

No, it varies depending on tissue types, developmental stage, pathological status

Question 11

collagen is produced by

Answer 11

fibroblasts, osteoblasts, chondroblasts

Question 12

the basic unit of collagen is

Answer 12

tropocollagen, which is a triple helix formed by 3 alpha polypeptide chains, enriched in glycine and Pro,HydroxyPro. They do not contain Cys, Trp

Question 13

each tropocollagen alpha chain has x aa

Answer 13

1000

Question 14

how many types of collagen are there

Answer 14

28

Question 15

which direction is the helix turn of one of the tropocollagen alpha chains

Answer 15

left-handed helical structure

Question 16

what direction is the helix turn once all three alpha chains are bound together

Answer 16

right handed triple helix

Question 17

the repeated aa sequence of collagens is

Answer 17

glycine, proline, hydroxyproline. (The side chains of the Pro/Hyp form lateral interactions with other triple helices)

Question 18

the H bonds in the CTH are between

Answer 18

NH2 group of Gly residues on one chain, and the CO group of the Pro/Hyp residues on neighbouring chains

Question 19

what collagen types are fibril forming

Answer 19

1, 2, 3, 5, 11

Question 20

most common types of collagen are

Answer 20

1: skin, tendon, heart, bone
2: cartilage
3: reticular CT
4: forms basal lamina, epithelium secreted layer of basement membrane
5: cell surfaces, liver, cornea, mucosa

Question 21

list the types of non-fibrillar collagens

Answer 21

• network forming (4, 8, 10)
• facit (9, 12, 14, 16, 19)
• anchoring collagens (7)
• short chains (8, 10)
• multiplexin (15, 18)
• macit (13, 17)

Question 22

how are type 1 collagens structured

Answer 22

each triple helix is displaced by 1/4 length (35nm) from its neighbour This is called a quarter staggered array. This helps form the banded pattern of collagen.

Question 23

how are type 1 collagen fibrils assembled?

Answer 23

it is determined by chain recognition sequence in the C - propeptide

Question 24

descemets membrane in the cornea is made of what type of collagen

Answer 24

VIII

Question 25

the basement membrane of glomerulus of kidney is formed by

Answer 25

type IV

Question 26

anchoring collagens connect x to y

Answer 26

epithelium to stroma

Question 27

beaded filament forming collagens form

Answer 27

structural links with cells, are type VI, it is crosslinked into tetramers that assemble into microfibrils

Question 28

elastin is found in what tissues

Answer 28

arteries, lungs, bladder, skin, elastic ligaments, cartilage

Question 29

how many genes are present for elastin

Answer 29

one, it contains Gly, Val, modified Ala and Pro. tropoelastin does not contain hydroxylysine nor is it glycosylated

Question 30

note

Answer 30

The lysines are involved in intermolecular crosslinking, while the week interactions between valine residues in the hydrophobic domains impart elasticity to the molecule. • Tropoelastin is highly cross-linked to form insoluble complexes.

Question 31

what does lysyl oxidase do

Answer 31

converts amine groups of lysine to form reactive aldehydes, this results in spontaneous formation of desmosine cross links

Question 32

structure of elastin

Answer 32

is made of elastin fibers (made of a core region enriched in elastin proteins surrounded by microfiber sheath)