Extracellular Matrix (ECM)

Question 1

What is the ECM?

Answer 1

ECM is a 3D network of proteins and molecules surrounding and supporting the cells and tissues.

Created by cells.

Question 2

Is the ECM small and mat-like in the connective tissue or the epithelial tissue?

Answer 2

Epithelial tissue

Question 3

What is the structure of the ECM in the tendon for high tensile strength?

Answer 3

rope-like

Question 4

Two reasons why ECM is important?

Answer 4

1. structural
2. cell behaviour (cues given from ECM substrate to cells)

Question 5

Which cell type secretes the ECM in connective tissues?

Answer 5

fibroblasts

Question 6

Which type of fibroblasts form cartilage?

Answer 6

chondroblasts

Question 7

Which type of fibroblast forms bone?

Answer 7

osteoblasts

Question 8

What are the three major classes of ECMs?

Answer 8

1. proteoglycans and glycosaminoglycans (GAGs)
2. fibrous proteins
3. glycoproteins

Question 9

Which ECM class are these proteins found in?
- hyaluronan
- perlecan
- decorin
- aggrecan

Answer 9

proteoglycans and glycosaminoglycans (GAG)

Question 10

Which ECM class are these proteins found in?
- type IV collagen
- fibrillar collagen

Answer 10

fibrous proteins

Question 11

Which is the largest class of ECM proteins?

Answer 11

glycoproteins

Question 12

Which ECM class are these proteins found in?
- laminin
- nidogen
- fibronectin

Answer 12

glycoproteins

Question 13

How many ECM proteins do mammals have?

Answer 13

300

Question 14

What are the two types of ECM assemblies distinguished between tissues?

Answer 14

• Basal lamina (basement membrane)
• Connective tissue

Question 15

Where do you find basal laminae?

Answer 15

it underlies all epithelial and surrounds some non-epithelial cell types incl.
- multinucleated muscle fibre in skeletal muscle
- entire length of myelin sheath

Question 16

What is the primary function of the basal membrane?

Answer 16

Provide mechanical stability

Question 17

What are some other functions the basement membrane may have?

Answer 17

Selective filter
Determines cell polarity
Can influence cell behaviour
Highway for cell migrations

Question 18

What is carcinoma?

Answer 18

cancer of the epithelial cell

Question 19

How do cancer cells eat through the basement membrane?

Answer 19

Express matrix metalloproteases - enzymes capable of degrading ECM proteins

Question 20

What are the interwoven networks of the basal laminae?

Answer 20

1. Laminin network
2. Perlecan network
3. Type IV collagen

Question 21

Which mesh-works does nidogen bind to in basement membrane?

Answer 21

Laminin
Type IV collagen

Question 22

How do cells interact with type IV collagen and laminin on basement membrane?

Answer 22

via intern heterodimers

Question 23

What are the primary organisers of the basal lamina sheet?

Answer 23

Laminin

Question 24

What are the three subunits of laminin? What shape do they make?

Answer 24

alpha chain
beta chain
gamma chain

crucifix shape

Question 25

How many genes encode for laminin?

Answer 25

11

Question 26

Basal epithelial cells are attached to basement membrane. What attaches them?

Answer 26

Hemidesmosomes

Question 27

What are hemidesmosomes?

Answer 27

Cell-matrix junctions that help anchor the epithelial cells to the basement membrane

Question 28

What diseases can mutations in hemidesmosome proteins lead to?

Answer 28

severe skin blistering diseases

Question 29

What family of proteins does collagen belong to?

Answer 29

fibrous proteins

Question 30

Which tissue type secretes collagen in large quantities?

Answer 30

connective tissue

Question 31

How many chains of alpha polypeptide are there in collagen?

Answer 31

3 in left handed helix

Question 32

What is the triplet series in collagen's alpha chain?

Answer 32

glycine - x - y x usually is proline y usually is hydroxyl proline

Question 33

How many genes code for collagen alpha chains?

Answer 33

42

Question 34

Which types of collagens do we find in connective tissue/ECM?

Answer 34

fibril forming collagen fibril-associated collagen

Question 35

Which collagen is an essential part of hemidesmosomes?

Answer 35

transmembrane collagen

Question 36

Which type of collagen is found in basal laminae?

Answer 36

network-forming collagen

Question 37

Which type of collagen forms a network/sheet?

Answer 37

type IV collagen

Question 38

What is the difference between fibril forming collagen vs type IV collagen?

Answer 38

fibril forming collagen is more rigid and elongated

Question 39

What is the function of the neuromuscular junction (NMJ)?

Answer 39

The NMJ relays signals between the axon terminal of a motor neuron and a skeletal muscle fiber, allowing muscle contraction

Question 40

What happens to the motor nerve cells when a skeletal muscle injury cuts a nerve?

Answer 40

The motor nerve cells connected to the muscle fiber degenerate.

Question 41

Why is the basal lamina around the neuromuscular junction able to direct nerve regeneration?

Answer 41

Unique composition of basement membrane different to that of the surrounding muscle Guides nerve (but not muscle) regeneration

Question 42

What do motor neurone axons deposit at at NMJ?

Answer 42

the neurotransmitter acetylcholine (ACh).

Question 43

What do muscle cells deposit at the NMJ?

Answer 43

laminin

Question 44

What is the main component of ground substance?

Answer 44

glycosaminoglycans (GAG)

Question 45

Which cell secretes and remodels the ECM in connective tissue?

Answer 45

fibroblast

Question 46

Are the long unbranched polysaccharide chains negative or positively charged?

Answer 46

highly negatively due to sulphates and carboxyl groups on sugars

Question 47

Are GAGs hydrophilic or hydrophobic?

Answer 47

hydrophilic

Question 48

What are the four types of GAGs?

Answer 48

1. Hyaluronic acid 2. Chondroitin sulphate 3. Heparin sulphate 4. Keratan sulphate

Question 49

What is created when GAGs bind to a core protein?

Answer 49

proteoglycan

Question 50

Which GAG does not form a proteoglycan?

Answer 50

hyaluronic acid

Question 51

Where and what synthesises hyaluronic acid?

Answer 51

Hyaluronan synthase enzyme On the plasma membrane

Question 52

Where are the GAGs bound to core proteins?

Answer 52

Golgi apparatus

Question 53

What is added to a serine on the core protein?

Answer 53

tetrasaccharide

Question 54

What makes up the proteoglycan Aggrecan?

Answer 54

Chondroitin sulfate Keratan sulfate Core protein

Question 55

Are decorin and perlecan GAGs or proteoglycans?

Answer 55

proteoglycans

Question 56

Which protein type can act as reservoirs due to their binding of signalling molecules?

Answer 56

proteoglycans

Question 57

Which GAG forms a hydrogel?

Answer 57

hyaluronic acid

Question 58

What does hyaluronic acid molecules attract (due to their negative charge)? Hint: not water

Answer 58

A cloud of positively charged sodium ions

Question 59

What does the cloud of positively charged sodium ions surrounding hyaluronic acid attract?

Answer 59

Water

Question 60

What is a medical application of hyaluronic acid?

Answer 60

Inject hyaluronic acid into knee joint of those with cartilage damage. Hydrogel forms in knee and eases symptoms from grinding.

Question 61

Organisation of collagen fibrils. Fill in gaps: Precursor alpha chain Proollagen triple helix (loose ends) Collagen molecule ? Collagen fibre

Answer 61

Collagen fibril

Question 62

How do the three alpha chains assemble into a procollagen?

Answer 62

via pro collagen peptidase

Question 63

Lysyl oxidase (LOX) deaminates lysine and hydorxylysine residues on collagen. Causes reactive aldehyde groups. What type of links are formed from this?

Answer 63

covalent links

Question 64

Which are larger and stronger, collagen fibrils or collagen fibres?

Answer 64

collagen fibres

Question 65

Which type of collagen helps form fibres from fibrils?

Answer 65

Fibril-associated collagens

Question 66

What is a main function of collagen fibrils/fibers?

Answer 66

Resistance against tensile stress (stretch)

Question 67

How does scurvy come about?

Answer 67

Vitamin C deficiency Less hydroxyproline Collagen triple helix cannot form

Question 68

What coils does elastin protein consist of?

Answer 68

alternating hydrophobic (random coils) and hydrophilic (alpha helical) domains

Question 69

Which tissues is elastin prominent in?

Answer 69

Ones that need to be elastic. E.g., artery Dermis