TLC - L4 - Extracellular matrix

Question 1

What are cell junctions?

Answer 1

Microscopic spaces between cells.

Question 2

What is the matrix?

Answer 2

Extracellular environment.

Question 3

What is the Basal Lamina?

Answer 3

Noncellular layer of ground substance lying just under epithelial surfaces.

Question 4

What is the function of the extracellular matrix?

Answer 4

• Determines properties of connective tissues.
• Provides ‘scaffold’ for tissue integrity.

Question 5

What’s the difference between connective tissue and extracellular matrix?

Answer 5

Connective tissue contains extracellular matrix + cells.

Question 6

How does the extracellular matrix influence cells?

Answer 6

By influencing:

• Shape.
• Migration.
• Proliferation.
• Function.
• Behaviour.
• pattern of development.

Question 7

How do cells influence the extra cellular matrix?

Answer 7

By influencing:

• Type of ECM produced.
• ECM turnover.

Question 8

What kind of relationship exists between cell and matrix?

Answer 8

Dynamic reciprocity.

Question 9

What controls extra cellular matrix organisation?

Answer 9

Cytoskeletal orientation.

Question 10

Is it possible for cells to both synthesize and degrade their own matrix?

Answer 10

Yes.

Question 11

What are the 2 main components of extra cellular matrix?

Answer 11

• Glysosaminoglycans (GAGs).
• Fibrous proteins.

Question 12

What are glycosaminoglycans (GAGs)?

Answer 12

Type of proteoglycan - Polysacharides covalently linked to protein.

Question 13

What are the main roles of fibrous proteins?

Answer 13

• Structural.
• Adhesive.

Question 14

Name 3 features of glycosaminoglycans (GAGs)?

Answer 14

• Un-branched.
• Composed of repeated disaccharides.
• Hydrophilic (negativeely charged).

Question 15

What’s the function of Glycosaminoglycans (GAGs)?

Answer 15

• Produces turger.
• Resist compression forces.

Question 16

What 2 alternating molecules make up the glycosaminoglycans (GAGs)?

Answer 16

• Uronic acid.
• Amino sugar.

Question 17

What’s the most simple form of glycosaminoglycan?

Answer 17

Hyaluronan.

Question 18

In what tissues is hyaluronan present?

Answer 18

In all tissues at different concentrations.

Question 19

What feature decides hyaluronans function?

Answer 19

Molecular weight.

Question 20

What are 3 functions of hyaluronan?

Answer 20

• Space filler.
• Facilitates cell shape-changes.
• Lubricant.

Question 21

What are the 2 components of a proteoglycans?

Answer 21

• Protein core.
• Glycosaminoglycan side chains.

Question 22

What kind of linkage exists between hyaluronan and proteglycans?

Answer 22

Ionic Linkage.

Question 23

What enzyme was injected to degrade the protein core in the proteoglycans in rabbit ears?

Answer 23

Papain.

Question 24

What is the most abundant animal protein?

Answer 24

Collagens.

Question 25

Why do **collagens** have **high tensile strength**?

Answer 25

* Long, inflexible **triple helix**. * **Covalent** cross-linked.

Question 26

How many different **alpha-chains** exist?

Answer 26

25

Question 27

What are **collagen fibres** core **function**?

Answer 27

Resist **tension.**

Question 28

What do **fibril-associated molecules** that are attached to collagen fibrils do?

Answer 28

Maintains **random organisation** of fibres.

Question 29

What is fibronectin?

Answer 29

A very **adhesive** **glycoprotein** used to pann for stem cells.

Question 30

What roles does **fibronectin** play?

Answer 30

* Adhesion. * Migration. * Growth. * Differentiation.

Question 31

What kind of molecules regulate the **activity of signalling molecules**?

Answer 31

Proteoglycans.

Question 32

How do proteoglycans **regulate** the activity of signalling molecules?

Answer 32

Binding **proteolytic enzymes** and **inhibitors**

Question 33

What does **syndecan** do?

Answer 33

Increases cell proliferetion.

Question 34

What is **syndecan**?

Answer 34

Family of **proteoglycans**.

Question 35

What **synthesizes** the **basal lamina**?

Answer 35

Cells for which it forms a base.

Question 36

What's the function of the **basal lamina**?

Answer 36

* **Seperates** different cell layers. * **'Scaffold'** for cell differentiation. * Molecular filter.

Question 37

What are the **2** main **functions** of **cell junctions**?

Answer 37

* Act as a **barrier** to water, solutes and cells. * Create an **integrated** view of environment.

Question 38

What are the **3 classes** of **cell junction**?

Answer 38

* Tight junction. * Anchoring junction. * Gap junction.

Question 39

What do **tight junctions** do?

Answer 39

Seal cells into a **sheet** and **prevent leakage** of molecules across sheet.

Question 40

What do **anchoring junctions** do?

Answer 40

**Mechanically** attach cells to their **neighbours** or to their extra cellular matrix.

Question 41

What do **gap junctions** do?

Answer 41

Allow **chemical** and **electrical signals** (ions) to pass between communicating cells.

Question 42

Can **tight junctions** **regulate their permeability**?

Answer 42

Yes.

Question 43

What are the **2** classes of **anchoring junctions**?

Answer 43

* Actin-dependant. * Intermediate filament-dependant.

Question 44

What is a **connexon** structure?

Answer 44

Controlled gap junction.

Question 45

How many **connexin sub-units** does a **connexon structure** contain?

Answer 45

6

Question 46

Why do **electrically excitable cells** have **gap junctions**?

Answer 46

* Synchronise cell populations. * Spread electrical signals rapidly.

Question 47

Why do **non-excitable cells** have **gap junctions**?

Answer 47

* Propagate responses (cAMP flow). * Supply positional information. * Coordinate development.