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BIOL 2321 - Cell Biology > Extracellular Matrix > Flashcards

Extracellular Matrix Flashcards

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1
Q

T or F: tissues are made up solely of living cells

A

FALSE! most of the material in our bodies is made from the ECM secreted by living cells

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2
Q

What things in our bodies is the ECM a large component of?

A

bones

cartilage

tendons

ligaments

cornea

exoskeletons in arthropods

the ‘jelly’ part of jellyfish

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3
Q

What does the ECM contribute to?

A

mass, strength, shape and form of organs

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4
Q

what 2 things is the ECM composed of?

A

proteins and polysaccharides

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5
Q

How do the components of the ECM assemble to make the ECM?

A

proteins and polysaccharides assemble into an organized meshwork

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6
Q

In addition to being packing material and a glue to hold cells together, what other functions does the ECM have?

A

it provides biochemical and mechanical signals that regulate the activities of the cell

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7
Q

T or F: every ECM has the same function

A

false! the function depends on the specific components present

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8
Q

what two cells are components of the outer layers of human skin (aka epithelium)?

A

epidermal cells

dermal cells

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9
Q

Describe how epidermal cells are situated to one another

A

they are tightly packed to one another and to an underlying ECM layer (basement membrane)

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10
Q

Describe the basement layer

A

a layer of ECM under the epidermal cells of the epithelium which they pack tightly to

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11
Q

T or F: epidermal cells have an extensive ECM

A

false - they do have ECM but not as much as dermal cells

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12
Q

Describe how dermal cells situate themselves to one another

A

they are located below the epidermis and are loosely packed with few cell-cell connections but a lot of ECM between

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13
Q

T or F: dermal cells have a lot of cell-cell connection and therefore not much ECM

A

false!! few cell-cell connections - they are loosely packed and therefore have lots of fibrous ECM between them

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14
Q

The dermis region consists of what type of tissue? what does this mean?

A

connective tissue

means there’s a lot more ECM present than cells

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15
Q

What do many dermal cells of dermis connective tissues have?

A

cell-surface receptors

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16
Q

What is the function of the cell-surface receptors in the dermis connective tissue?

A

they secrete the ECM and allow communication between the intra- and extracellular environments

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17
Q

List 7 components of the ECM

A

glycocalyx

basement membrane (basal lamina)

collagen

elastin

proteoglycans

fibronectins

integrins

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18
Q

Where would a glycocalyx be located?

A

around every cell

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19
Q

Describe the glycocalyx

A

a network of sugars made of glycoproteins and glycolipids embedded in the membrane (sugars facing outwards) that were synthesized in the ER and processed in the Golgi

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20
Q

What are the 2 components of the glycocalyx?

A

glycoproteins

glycolipids

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21
Q

What are the 3 functions of the glycocalyx?

A

gives each cell an identity that can be recognized by other cells in the body

provides some mechanical protection

mediates cell interactions (with other cells or ligands)

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22
Q

What is another name for the basement membrane?

A

basal lamina

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23
Q

Describe the basement membrane/basal lamina

A

a thin, tough, flexible continuous sheet of matrix molecules beneath every epithelial tissue

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24
Q

T or F: the basal lamina is a continuous layer beneath epithelial cells

A

true

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25
Q

How thick is the basal lamina?

A

50-200 nm

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26
Q

What is the main component of the basal lamina?

A

collagen protein

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27
Q

What type of organisms have basal lamina?

A

all multicellular animals

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28
Q

What type of cells is the basal lamina mostly associated with?

What other cells can the basal lamina surround?

A

associated with epithelial cells

but can also surround individual fat cells, muscle cells, and Schwann cells

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29
Q

What are the 4 functions of the basement membrane/basal lamina?

A

separates epithelial cells from the underlying or surrounding connective tissue

provides mechanical support for epidermal cells

creates water-tight barrier to molecular passage

provides a scaffold for regenerating cells if skin is damaged

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30
Q

What results from genetic defects in the basal lamina?

A

the epidermis detaches from the dermis which can cause severe and painful blisters

can also cause some muscular dystrophy (muscles degenerate later in life)

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31
Q

What are the 5 components of connective tissues?

A

collagen

elastin

proteoglycans

fibronectins

integrins

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32
Q

Describe collagen

A

huge protein fibres made of thousands of individual collagen molecules

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33
Q

Where does the assembly of collagen fibres occur?

A

outside the cell

34
Q

How thick can collagen fibres be?

A

up to 100 nm

35
Q

What is the main function of collagen?

A

to provide a structural framework for the ECM

36
Q

How many different types of collagen are there throughout the body?

A

28

37
Q

Approximately how much of all the protein in your body is collagen?

A

1/4

38
Q

Describe the structure of collagen and how it packs together to make fibres

A

a triple helix (3 tightly wound chains around each other)

these triple helices are packed into repeating rows in staggered alignment

39
Q

What is the function of collagen?

A

collagen fibre is very strong and flexible to provide the structure and strength for tissues

40
Q

T or F: collagen is strong and rigid

A

False, it is strong and flexible

41
Q

How does elastin compare to collagen?

A

elastin: smaller, not as strong, more resilient

42
Q

Where is elastin found?

A

in elastic tissues like the skin and some cartilages (ex. nose, ear)

43
Q

Describe the structure of elastin

A

smaller, less strong fibres than collagen, but very elastic and resilient

they cross-link to provide strength

44
Q

What is the MAIN function of elastin? What other functions does it have?

A

it provides some strength but the main function is to stretch out and spring back to make tissues more elastic

45
Q

How do elastins pack together?

A

they cross-link into very dense networks

46
Q

Describe proteoglycans

A

small protein fibres with negative charges that are attached to long linear oligosaccharides that fill in the ECM with a porous, hydrated gel

47
Q

Describe glycosaminoglycans (GAGs)

A

repeating sulfonated sugars that compose the oligosaccharides bound to proteoglycans

48
Q

What type of oligosaccharides bind to proteoglycans?

A

repeating sulfonated sugars called glycosaminoglycans (GAGs)

49
Q

What does GAG stand for?

A

glycosaminoglycan

50
Q

Give 3 examples of GAGs

A

chondroitin sulfate

keratan sulfate

hyaluronan/hyaluronic acid

51
Q

What is the function of proteoglycans? How do they achieve their function?

A

they form a porous hydrated gel that fills in the ECM

they can do this because they have many negative charges = good at binding water

52
Q

What type of charge do proteoglycans have? why?

A

negative charges to bind water to make a hydrated gel to fill in the ECM

53
Q

How do proteoglycans arrange themselves to make the porous hydrated gel of the ECM?

A

Many proteoglycans attach to a central long hyaluronic acid GAG strand to form huge aggregates

54
Q

What does hyaluronic acid form?

A

a viscous non-compressible solution

55
Q

Where is hyaluronic acid present? What is its function?

A

in fluid in the cavities of synovial joints to reduce friction during movement

it’s also the jelly-like vitreous humor of your eye

56
Q

What do a lot of glycoproteins have? What is the purpose of this?

A

multiple binding sites that help the cell attach to the ECM components

57
Q

Describe fibronectin

A

a dimeric glycoprotein that functions in many cell-ECM interactions

58
Q

What is the function of fibronectin?

A

to assist in cell-ECM interactions

59
Q

In what ways does fibronectin assist in cell-ECM interactions?

A

binds to cell surface receptors (with RGD sequence)

have other binding domains to bind other molecules (ex. collagen)

help determine cell shape

help determine direction of any cell migration

critical for development

60
Q

What structure does fibronectin have?

A

dimer

2 subunits joined at the C-termini by disulfide bridges and contain similar binding domains

61
Q

what sequence causes fibronectin to bind to cell surface receptors?

A

RGD sequence

62
Q

Use an example to explain why fibronectin is critical for development

A

mutant mice without fibronectin die in early embryonic development

63
Q

Where do the 2 subunits of fibronectin join?

A

at the C-termini via disulfide bridges

64
Q

T or F: the binding domains on the two subunits of fibronectin are different

A

false, they are usually very similar

65
Q

What are 2 major functions of fibronectin?

A

determining cell shape

directed cell migration

66
Q

Describe integrins

A

A family of membrane receptors in animals that bind to ECM molecules

67
Q

Describe the structure of integrins

A

heterodimers with an alpha and beta subunit

globular heads on the EC side that are curled when inactive and straight when active

68
Q

What do integrins have on their EC side?

A

globular heads

69
Q

What conformation do the globular heads of integrins have when they are inactive?

A

curled

70
Q

What conformation do the globular heads of integrins have when they are active?

A

straight

71
Q

What is the main function of integrins? How do they accomplish this?

A

they bind to the cytoskeleton on the cytoplasmic side of the membrane so they can bind to many extacellular molecules and promote ECM adhesion and communication

think: integrin = integrate ECM signals and communicate to inside of cell

72
Q

What would activate an integrin?

A

binding of a ligand (ex. collagen)

they are membrane receptors, so they require a ligand to bind to create a conformational change

73
Q

What is required to induce the straightened conformation of integrins?

A

binding to the cytoskeleton on the cytoplasmic side of the membrane

74
Q

What does the binding of ECM fibres to integrins cause?

A

the activation of kinase cascades in the cytoplasm

75
Q

What binds to integrins to cause kinase cascades in the cytoplasm?

A

ECM fibres

76
Q

What can an integrin binding to an ECM molecule effect?

A

cell survival

growth

migration

differentiation

77
Q

What is the RGD sequence?

A

Arginine-Glycine-Aspartate

78
Q

Where are RGD sequences found?

A

on fibronectin, collagen, and other integrin targets

79
Q

T or F: RGD is the most common sequence where integrin will bind

A

true

80
Q

Describe how blood clotting at injury sites occurs?

A

platelets in blood plasma bind to the fibrinogen ECM proteins with an RGD sequence and then they bind to each other using integrins

81
Q

How can blood clotting be limited?

A

drugs with RGD sequences can prevent the interactions between platelets in blood plasma, fibrinogen, and integrins

BIOL 2321 - Cell Biology (26 decks)

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