Extracellular Matrix

Question 1

ECM provides ?

Answer 1

Support, strength, framework and protection

Question 2

What is the difference in ECM between animals and plants ?

Answer 2

In animals:

• Strong
• Agile
• Motile
• Flexible

In plants:

• Weak
• Fragile
• Rigid
• Thin

Question 3

Plant cell strength comes from ?

Answer 3

Cell wall

Question 4

Cell walls composed of ?

Answer 4

Polysaccharides

Question 5

Mainly composed of ?

Answer 5

Cellulose (inner layers) and pectin (outer layers)

Question 6

Help to maintain and control?

Answer 6

Internal osmotic swelling

Question 7

What is the most abundant organic macromolecule on earth ?

Answer 7

Cellulose

Question 8

Cellulose microfibrils arranged in ?

Answer 8

Crisscross lattice interwoven with other polysaccharides and structural proteins

Question 9

What does this arrangement provide ?

Answer 9

Tensile strength and resists compression

Question 10

Orientation of cellulose microfibrils dictates direction of ?

Answer 10

Cell growth and elongation

Question 11

Membrane attached microtubules guide ?

Answer 11

Location of enzyme complexes for cellulose formation

Question 12

Cytoskeleton controls ?

Answer 12

Plant shape and tissue modelling

Question 13

Connective tissue contains ?

Answer 13

Most ECM

Question 14

Highly varied tissues, varying from ?

Answer 14

Hard (bone), flexible (tendons), rubber (cartilage) or soft (jelly-like substance in eyes)

Question 15

Explain ECM - Fibroblasts ?

Answer 15

• ECM laid down by fibroblasts
• Elongated, spindle-shaped cells
• Attach to and secrete collagen
• Cancer-associated fibroblasts (CAFs) contribute to malignancy

Question 16

Fibroblasts scattered amongst ?

Answer 16

ECM

Question 17

Explain ECM - Collagen ?

Answer 17

• 20 collagen genes in mammals
• Encode different collagen types
• Constitute ~25% protein mass in mammals
• Long, stiff triple helical structure
• Collagen molecules can assemble into polymers = collagen fibrils
• Collagen fibrils can pack together further = collagen fibers

Question 18

Explain Collagen synthesis (ECM) ?

Answer 18

• Collagen synthesis completed outside of cell
• Precursor procollagen made inside cells and secreted by exocytosis
• Procollagen contains peptide extensions that prevent collagen microfibril formation
• Enzymes called procollagen proteinases cut terminal extensions
• Collagen formed and assembled only in the extracellular space

Question 19

Explain Collagen organisation ?

Answer 19

• Collagen deposition must be coordinated for proper connective tissue function
• Collagen deposited then rearranged by fibroblasts
• Fibroblasts crawl over collagen fibers compacting and aligning

Question 20

Ehlers-Danlos Syndrome (EDS) collection of ?

Answer 20

Rare inherited conditions affecting connective tissue

Question 21

What does EDS lead to ?

Answer 21

Stretchy skin, hypermobility in joints

Question 22

What do serious cases cause?

Answer 22

Vasculature weakness

Question 23

Is there a treatment available for EDS ?

Answer 23

No treatment available, lifestyle management, physiotherapy

Question 24

Cells do not attach well to ECM – instead use ?

Answer 24

A collagen-fibronectin-integrin axis

Question 25

Fibronectin secreted by ?

Answer 25

Fibroblasts – one part binds collagen, other part binds cell

Question 26

Cell attaches to fibronectin through ?

Answer 26

Receptor proteins called integrins