ECM

Question 1

What is the extracellular matrix (ECM)?

Answer 1

Materials released to cell exterior that assemble into a 3D extracellular structure

Question 2

What are the main features of ECM?

Answer 2

Fibrous network and gel-like background matrix

Question 3

What do plant ECMs consist of?

Answer 3

Polysaccharide fibres (cellulose

Question 4

What do animal ECMs consist of?

Answer 4

Fibrous protein fibres (e.g. collagen) in a glycosaminoglycan matrix

Question 5

What surrounds all plant cells?

Answer 5

A thick layer of specialised ECM called the cell wall

Question 6

What is the plant cell wall made of?

Answer 6

Carbohydrates and a small amount of proteins

Question 7

What are the main fibrous components of the plant cell wall?

Answer 7

Cellulose fibres crosslinked by hemicellulose

Question 8

What is the plant ECM gel matrix made of?

Answer 8

Negatively charged pectins

Question 9

What role does the plant cell wall play?

Answer 9

Provides rigidity and strength

Question 10

How does turgor pressure affect plant cells?

Answer 10

Osmosis draws water in

Question 11

What happens when plants lack water?

Answer 11

Loss of turgor pressure causes wilting and structural weakness

Question 12

What are some plant parts reinforced with?

Answer 12

Extra cell wall making them stronger and turgor-independent

Question 13

What are the three layers of the plant cell wall?

Answer 13

Primary cell wall

Question 14

What forms the middle lamella?

Answer 14

Fusion of vesicles after cell division

Question 15

What is the primary cell wall?

Answer 15

The first wall synthesized

Question 16

What is the secondary cell wall?

Answer 16

Formed after expansion stops

Question 17

What is the middle lamella made of?

Answer 17

Pectins and some proteins

Question 18

What is pectin composed of?

Answer 18

Chains of galacturonic acid molecules

Question 19

Why is pectin highly hydrated?

Answer 19

Due to high charge and binding with Ca2+ and Mg2+

Question 20

What is the primary cell wall made of?

Answer 20

Cellulose

Question 21

What is cellulose?

Answer 21

A straight glucose polymer forming rigid microfibrils with high tensile strength

Question 22

What is hemicellulose?

Answer 22

A branched sugar polymer that crosslinks cellulose for strength

Question 23

What do proteins in the primary cell wall do?

Answer 23

Remodel wall composition during events like fruit ripening

Question 24

Where is the secondary cell wall located?

Answer 24

Between the plasma membrane and primary cell wall

Question 25

What are components of the secondary cell wall?

Answer 25

Cellulose fibres

Question 26

What is lignin?

Answer 26

Branched aromatic polymer in wood that adds strength

Question 27

What are the three major classes of animal ECM?

Answer 27

Fibrous proteins

Question 28

What is the most abundant protein in mammals?

Answer 28

Collagen

Question 29

What does collagen provide?

Answer 29

Tensile strength and structural support

Question 30

How many types of collagen exist in vertebrates?

Answer 30

Around 28

Question 31

Where is collagen found?

Answer 31

Skin

Question 32

What is the structure of collagen?

Answer 32

Triple-stranded helix of three alpha chains

Question 33

What amino acids are rich in collagen?

Answer 33

Glycine and proline

Question 34

What stabilises the collagen helix?

Answer 34

Hydrogen bonds

Question 35

What are the steps in fibrillar collagen synthesis?

Answer 35

Intracellular: translation

Question 36

Which collagen types are fibrillar?

Answer 36

Type I

Question 37

Where is type IV collagen found?

Answer 37

Basement membrane

Question 38

Functions of type IV collagen?

Answer 38

Structural support

Question 39

What do elastic fibres do?

Answer 39

Provide tissue elasticity and recoil

Question 40

What are elastic fibres made of?

Answer 40

Elastin and microfibrils

Question 41

How do elastin molecules behave?

Answer 41

Extend and contract like a coil

Question 42

What promotes elastin recoil?

Answer 42

Exposed hydrophobic regions during stretch

Question 43

What makes up elastin?

Answer 43

Repeating hydrophobic pentapeptides

Question 44

Why is balance between elastin and collagen important?

Answer 44

Prevents hyperelasticity

Question 45

What are GAGs?

Answer 45

Highly hydrated unbranched polysaccharide chains

Question 46

What is the structure of GAGs?

Answer 46

Repeating disaccharide units of amino sugar + uronic acid

Question 47

What makes GAGs hydrophilic?

Answer 47

Sulphate and carboxyl groups

Question 48

Why do GAGs occupy large volume?

Answer 48

Negative charge promotes extended conformation

Question 49

What are examples of GAGs?

Answer 49

Hyaluronan

Question 50

What is hyaluronan?

Answer 50

Simplest GAG made of identical disaccharide units

Question 51

What sugars make up hyaluronan?

Answer 51

N-acetylglucosamine and glucuronic acid

Question 52

Functions of hyaluronan?

Answer 52

Osmotic pressure maintenance

Question 53

What are proteoglycans?

Answer 53

GAGs covalently linked to protein core

Question 54

What is aggrecan?

Answer 54

A proteoglycan forming aggregates with hyaluronan and link proteins

Question 55

What does aggrecan do?

Answer 55

Binds water to create osmotic pressure and withstand compression

Question 56

How does aggrecan respond to compression?

Answer 56

Water is displaced and returns when relaxed

Question 57

What maintains tissue integrity with aggrecan?

Answer 57

Collagen fibrils

Question 58

What are glycoproteins?

Answer 58

Proteins with short branched sugar side chains

Question 59

What is the function of glycoproteins?

Answer 59

Bind cells and ECM for network structure

Question 60

What is fibronectin?

Answer 60

A multidomain glycoprotein that binds ECM components

Question 61

Functions of fibronectin?

Answer 61

ECM organisation

Question 62

Where is fibronectin used?

Answer 62

Seeded on Matrigel

Question 63

What is laminin?

Answer 63

A heterotrimeric glycoprotein with α

Question 64

Functions of laminin?

Answer 64

Self-assembly