Extracellular matrix

Question 1

Define the extracellular matrix

Answer 1

The ECM refers to a complex network of macromolecules that are synthesised, secreted and assembled by the cells

Question 2

Do all tissues comprise of the same ECM

Answer 2

No. They may have similar compositions but it all depends on the tissue function

1) Bones = Calcified
2) Cornea = Transparent
3) Tendon = Rope- like
4) Blood = Fluid

Question 3

What are the two main functions of the ECM

Answer 3

1) Provides structural support
- Adhesive scaffold
- mechanical strength

2) Plays a role in cell signalling

Question 4

What are the 4 major macromolecules found in the ECM

Answer 4

1) GAGs = Glycosaminoglycans

2) Proteoglycans

3) Fibrous proteins : Collagen and Elastin

4) Adhesive Glycoproteins
- Fibronectin
- Laminin

Question 5

Describe the structure of GAGs

Answer 5

• These are long unbranched polysaccharides
• They contain repeating disaccharide units
  eg) Amino suagrs and Uronic acid
• They are highly negatively charged

Question 6

What are the properties of GAGs

Answer 6

1) They are strongly hydrophylic

2) They form hydrated gels

3) They occupy large extracellular volume

Question 7

State the function of GAGs

Answer 7

1) They resist compressive forces
2) Attract Na+
3) They allow rapid diffusion of molecules

Question 8

What is hyaluranate

Answer 8

• These are the simplest GAGs
• They contain extremely long chains
• They do not contain sulphate suagrs
• They are not covalently attatched to a protein

Question 9

List the functions of hyaluranate

Answer 9

1) Act as space fillers
2) Used for tissue repair
3) Joint lubrication

Question 10

Describe the structure of proteoglycans and describe its synthesis process

Answer 10

• They contain a core protein and GAG chain
• They are synthesised in teh ribosomes and golgi apparatus

1) The protein is made in the ribosome
2) GAG chain is made in the golgi apparatus
3) The proetoglycans are excreted by exocytosis into the ECM

Question 11

Fibrous Proteins Collagen: Describe its features

Answer 11

• The most abundant ECM protein
• Rich in glycine and proline
• Triple helical

Question 12

List the types of collagen

Answer 12

1) Type 1 = Skin, Tendon and Bone

2) Type 2 = Cartiledge

3) Type 3 = Blood vessels and skin

4) Type 4 = Basal lamina

5) Type 5= Skin anchoring

6) Type 6/7 = fibril associated collagen

Question 13

Describe the different ways that collagen is organised in different tissues

Answer 13

1) In mamamlian skin = wickerwock pattern

2) In tendons = parallel bundles

3) Cornea and bone = Layered orthogonal arrays

Question 14

Fibrous Proteins: Elastin
Describe the structure

Answer 14

• Tropoelastin secreted
• Extensively cross-linked
• Forms elastic fibres and sheets

Question 15

Elastin : State the function

Answer 15

1) allows tissue to recoil and stretch

2) Works with collagen

Question 16

What is the basal lamina

Answer 16

The basal lamina is a specialised ECM sheet that seperates the epithelium from the connective tissue.

Question 17

List the major components of the basal lamina

Answer 17

1) Laminin
2) Type 4 collagen
3) Nidogen
4) Perlecan

Question 18

List the functions of the basal lamina

Answer 18

1) Mechanical support
2) selective support
3) Controls:
- cell polarity
- differentation
- survival

Question 19

Adhesive Glycoproteins Fibronectin : State the features

Answer 19

• There are loads of them in the ECM
• They have multiple binding domains such as : Collagen , intergrins and other ECM proteins

Question 20

function of fibronection

Answer 20

helps attatch cells to ECM