lecture 13 - the Extra cellular matrix

Question 1

What is a definition of the extra cellular matrix?

Answer 1

extracellular matrix (ECM) any substance produced by cells and secreted into the extracellular space within the tissues.

Question 2

What is the primary function of the ECM?

Answer 2

ECM provides physical support for cells and a linkage between different cells or tissues

Question 3

What is another function of the ECM?

Answer 3

Cell Motility – it forms a substrate on which cells can move and furthermore it provides cues that guide the direction of movement

Question 4

What is the basic cellular organisation In animals?

Answer 4

• epithelial tissue

- connective tissue

Question 5

What is the general composition the ECM?

Answer 5

• consists of scattered cells
• consists of collagen fibers (protein) cross-linked by accessory proteins in a matrix of proteoglycans (protein + polysaccharides)

Question 6

What is the scant ECM?

Answer 6

• consists of layers of cells closely bound to one another to form protective sheets

Question 7

What are the layers of the ECM?

Answer 7

• epithelial cells
• basal lamina
• collagen

Question 8

What is the purpose of the basal lamina?

Answer 8

provides a base for the cells to sit on and acts as a molecular sieve and substrate for migrating cells

Question 9

What is the ECM in plants?

Answer 9

The cell wall

Question 10

What is the composition of the cell wall?

Answer 10

consists of cellulose fibers (polysaccharide) cross-linked with hemicellulose in a matrix of highly branched polysaccharides (e.g. Pectin)

Question 11

How does the ECM differ between plants and animals?

Answer 11

plants contain polysaccharide fibres animal ECM has fibres made of protein whilst Animal ECM contains COLLAGEN & ELASTIN

Question 12

How many genes are in mammals which make up the collagen in the body?

Answer 12

42 different genes

Question 13

What proportion of the body does the % of collagen make up?

Answer 13

25%

Question 14

How is collagen formed?

Answer 14

• single collagen polypeptide chain
• triple- stranded collagen molecule
• collagen fibril

Question 15

What are the 5 steps of collagen formation steps within the cells?

Answer 15

1. • synthesis of a pro - alpha chain
     2 .- hydroxylation of selected prolines and lysines
2. • glycosylation of selected hydroxylysines
3. • self assembly of three pro- alpha chains
     5.- pro collagen triple helix formation

Question 16

What are collagen helical regions composed of?

Answer 16

composed of Gly-X-Y repeats, where X and Y can be any AA, but usually Pro and HydroxyPro, and less commonly Lys and HydroxyLys

Question 17

What does elastin do?

Answer 17

• provides elasticity to tissues

Question 18

How is elastin composed?

Answer 18

composed of large filaments with lots of random coils that can be compared to springs

Question 19

How is elastin connected?

Answer 19

by cross-linked Lysine or hydroxylysines

Question 20

What happens when elastin fibres are relaxed?

Answer 20

coiled up

Question 21

How is the ECM similar to the ECM in plants?

Answer 21

most of the matrix consists of polysaccharides

Question 22

What is the name of the polysaccharide in plants in the ECM?

Answer 22

pectin

Question 23

What is the name of the polysaccharide in animals?

Answer 23

Glycosaminoglycans

Question 24

What are the 3 different types of GLYCOSAMINOGLYCANS?

Answer 24

hyaluronan, chondroitin sulphate, heparan sulphate

Question 25

What is different about hyaluronan?

Answer 25

• does not form covalent cross linking

Question 26

What are glycosaminoglycans made of

Answer 26

Disaccharide = glucoronic acid or iduronic acid, and N-acetylglucosamine or N-acetylgalactosamine

The disaccharide is repeated along the chain .

Question 27

What do the types of connective tissue exist due to variation?

Answer 27

the relative proportion of fibres to cells within the ECM

the number and proportion of different cell types within the ECM

. the proportion and arrangement of the fibres in the ECM

the composition of the non-fibrous component of the ECM

Question 28

Who was Mr Morris and what was his symptoms?

Answer 28

• had very stretchy skin
• Connective tissue of the dermis is affected
• The component that stops it stretching too far is collagen. - Collagen is rigid won’t stretch too much
• The elastin fibres go much further than the collagen

Question 29

Why did Mr Morris’s collagen not form?

Answer 29

Failure of conversion of lysine to hydroxylysine by lysyl hydroxylase OR failure to cleave off propeptide termini
=> fibrils and fibres don’t form

Question 30

What does areolar connective tissue do in the body?

Answer 30

cushions the organs in out body . Made up of elastin and collagen, helps to encase internal organs

Question 31

What is adipose tissue made up of?

Answer 31

• collagen 3 and reticular fibres

Question 32

What are tendons and ligaments made up of?

Answer 32

• Dominant feature is not the cells but the collagen fibres

Question 33

What is the dermis of the skin made up of?

Answer 33

• collagen fibres and fibroblast nuclei

- collagen must be organised in a more variable way due to the skin being able to move more

Question 34

What is elastic collagen made up?

Answer 34

• elastin fibres

Question 35

What is different about bone?

Answer 35

Mineralised matrix , calcium rich cystal matrix that is crucial for bond strength

Question 36

What is the mechanism for scurvy?

Answer 36

Scurvy due to lack of Vit C (Ascorbic acid) essential cofactor for propel hydroxyls that make hyrdoxyPro and which needed for crosslinking of collagen fibres

Question 37

What are the symptoms of scurvy?

Answer 37

lack of nromal fibrils leads to fragility and bleeding and teeth loss, etc

Question 38

What does Fibrodysplasia ossificans progressiva

do?

Answer 38

Muscle and connective tissue like tendons are gradually replaced by bone (ossified