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BIO130 > 2.5: Interactions Between Cells and their Environment > Flashcards

2.5: Interactions Between Cells and their Environment Flashcards

1
Q

epithelial cells interact with each other and the extracellular matrix (ecm) through _______ to form ______

A

junctions, tissues

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2
Q

state the function of tight junctions

A

seals neighboring cells together in an epithelial sheet to prevent leakage of extracellular molecules between them; helps polarize cells

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3
Q

state the function of adherens junctions

A

joins an actin bundle in one cell to a similar bundle in a neighboring cell

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4
Q

state the function of desmosomes

A

joins the intermediate filaments in one cell to those in a neighbor

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5
Q

state the function of gap junctions

A

forms channels that allow small, intracellular, water-soluble molecules, including inorganic ions and metabolites to pass from cell to cell

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6
Q

state the function of hemidesmosome

A

anchors intermediate filaments in a cell to the basal lamina

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7
Q

how are gap junctions different from channels

A

Diff from channels bc channels connect cytosol and extracellular space
Gap junctions connect cytosol to cytosol

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8
Q

in polarized epithelial cells: are junctions arranged in a specific order or random

A

specific order

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9
Q

state the two cell-cell anchoring junctions (Attaching neighbouring cells to each other)

A

adherens junction, desmosome

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10
Q

state which is the cell-ecm anchoring junction (anchoring cell to the basal lamina)

A

hemidesmosome

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11
Q

what is the purpose of the adhesion belt

A

to connect a cell to the nearby ones

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12
Q

what is the purpose of the sealing strand (tight junction belt)

A

All along the cell forming the seal between cell on left and right and front

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13
Q

what is the visible difference between adhesion belt and sealing strand in a diagram

A

sealing strand is like criss cross and wider, adhesion belt is tighter

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14
Q

which membrane proteins do tight junctions prevent from mixing

A

the apical and basolateral membrane proteins

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15
Q

tight junctions form __________

A

sealing strands (tight junction belt)

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16
Q

which 2 transmembrane proteins (4 transmembrane domains weaving back and forth on the membrane) are tight junctions composed of

A

occludin and claudin

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17
Q

t/f tight junctions can block the movement of molecules from either side

A

true

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18
Q

are occludin and claudin only able to bind to itself

A

yes. only occludin-occludin and claudin-claudin on neighboring cells

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19
Q

regarding claudin and occludin, are they required in both cells? and what part of the cell do they interact with?

A

yes required in both cells, extracellular domain in one cell interacts with extracellular domain in neighbouring cell

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20
Q

transmembrane proteins link to _____________ inside the cel

A

cytoskeleton

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21
Q

anchoring junctions are able to provide what to the epithelium

A

mechanical strength

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22
Q

cell-cell anchoring junctions (adherens junctions, desmosomes) link cytoskeletons of ______________

A

neighboring cells

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23
Q

cell-ecm anchoring junctions (hemidesmosome) link cytoskeleton to ____________

A

basal lamina

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24
Q

for transmembrane adhesion proteins: what do the extracellular and intercellular domains interact with?

A

extracellular domains interact with adhesion proteins of neighbouring cells (side) or the ecm (bottom). intracellular domains interact with linker proteins

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25
Q

what is the role of intracellular linker proteins

A

cytosolic proteins, link transmembrane adhesion proteins to cytoskeletal filaments

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26
Q

each anchoring junction has specific ________________ and _____________

A

transmembrane adhesion proteins and intracellular linker proteins

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27
Q

_____________ forms an adhesion belt (encircles the inside of the plasma membrane)

A

adherens junctions

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28
Q

what are cadherins and their purpose

A

cadherins are transmembrane adhesion proteins. cadherin proteins from neighbouring cells interact with each other, and intracellular linker proteins link cadherin proteins to actin filaments

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29
Q

what protein forms adherens junctions when concentrated at sites of cell-cell interactions

A

form adherens junctions

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30
Q

compare and contrast between desmosomes and hemidesmosomes

A
  • both link to intermediate filaments eg keratin, intermediate filaments provide the most structural strength
  • desmosomes linked to keratin filaments and connect to a neighbouring cell
  • hemidesmosomes anchor keratin filaments to the basal lamina (type of ecm)
31
Q

what filaments provide the most structural strength

A

intermediate filaments

32
Q

describe desmosomes: eg what are they, where are they found, what proteins form it

A
  • formed by desmoglein, desmocollin
  • desmosomes are transmembrane adhesion proteins, specific cadherin family members (nonclassical)
  • intracellular linker proteins link desmoglein and desmocollin to keratin filaments inside the cell (like desmosomes are in between the two cells and then they link to linker proteins that are in the cells which have the keratin anchored to the linker on the cell inside)
33
Q

can desmoglein and desmocollin only bind to themselves

A

they can bind to themselves are each other

34
Q

what composes hemidesmosomes and where do they bind

A

integrins, bind to laminin in the basal lamina (ecm) – intracellular linker proteins link integrins to keratin filaments inside the cell

35
Q

differ between the role of intracellular linker proteins with desmosomes and hemidesmosomes

A

desmosomes: intracellular linker proteins link desmoglein and desmocollin to keratin filaments inside the cell
hemidesmosomes: link integrins to keratin filaments inside the cell

36
Q

gap junctions allow for __________ between cells

A

communication

37
Q

what are gap junctions composed of and describe the order of organization

A

1 subunit = connexin
6 connexin = form connexon (hemichanell)
2 connexons = intracellular channel (goes perpendicular to plasma membranes)

38
Q

around what size if the gap of gap junctions

A

2-4 nm

39
Q

for gap junctions: how do they couple cells, selectivity, what is allowed passage and what isn’t, any gating?

A
  • couple cells electrically (ions) and metabolically – cytosolic connections
  • not very selective as to what passes through: allows ions and metabolites <1000 daltons
  • passes through: cAMP, nucleotides, glucose, amino acids
  • not pass: macromolecules, proteins, nucleic acids
  • are gated - can be open or closed by extracellular or intracellular signals
40
Q

does dopamine open or close gap junctions

A

close

41
Q

does a dramatic increase in cytosolic ca2+ open or close gap junctions

A

close

42
Q

does membrane damage open or close gap junctions

A

membrane damage leads to ca2+ leaking into damaged cells = gap junctions close as to prevent the loss of metabolites from adjacent cells

43
Q

describe intracellular junctions in plant cells

A
  • lack cell junctions in animal cells
  • plants surrounded by cell walls: hold cells tgt and provide mechanical strength
  • plasmodesmata: intercellular junctions, allow for communication between cells, but need to cross cell wall (diff structure from gap junctions)
44
Q

what is the name of the cytoplasmic channels in plant cells and describe it

A

plasmodesmata - continuous plasma membrane and er across plasmodesmata

45
Q

explain intercellular movement in plant cells

A
  • plasmodesmata
  • small soluble molecules move freely (<1000 daltons) eg sugar, ions, other essential nutrients
  • controlled trafficking of large complex molecules under specific conditions: gating for proteins and regulatory RNAs
46
Q

explain the gating of plant plasmodesmata

A

gating: eg blocking movement of large complex molecules
ex: enhanced callose (plant polysaccharide) deposition controls permeability through reversible callose deposition – between two cells, callose makes the opening smaller which prevents any movement and also leads to pressure induced displacement (blocking the entrance) on the opposite cell that callose is on

47
Q

compare and contrast between epithelial tissues and connective tissues

A

epithelial:
- eg intestinal lining, skin epidermis
- cells closely associated
- cells are attached to each other w junctions and adhesions
- limited ecm (thin basal lamina)
- cytoskeletal filaments provide resistance to mechanical stress
connective tissue:
- eg skin dermis, bone, tendon, cartilage
- cells are rarely connected
- cells attached to matrix
- plentiful ecm
- ecm provides resistance to mechanical stress

48
Q

what are the 3 classes of macromolecules in the ecm

A
  1. glycosaminoglycans (gags) and proteoglycans
  2. fibrous proteins - collagens, elastin
  3. glycoproteins - laminin, fibronectin
49
Q

________ is the primary component in connective tissues

A

ecm

50
Q

does the composition of ecm lead to different properties of tissues

A

yes

51
Q

describe gags (glycosaminoglycans)

A
  • long, linear, chains of repeating disaccharide
  • highly negatively charges (attract na+ and h2o)
  • form hydrated gels which resist compression and fills space
  • most gags synthesized inside cell and released by exocytosis
52
Q

what is the key geature of hyaluronan and describe it

A

key feature: amino sugar
- simple gag
- long chain of repeating disaccharide subunits (up to 25000)
- hyaluronan is spun directly from cell surface by plasma membrane enzyme complex
- in the picture it says 300 nm and (8x10^6)

53
Q

apart from hyaluronan, give an example of a gag and is key feature

A

heparin - SO3 attached to CH2O and NH

54
Q

describe proteoglycans

A
  • subclass of glycoproteins
  • protein with at least one sugar side chain which must be a gag
  • typically, more extensive addition of sugars (can be up to 95% of total weight)
55
Q

describe the structure and properties of collagen (fibril forming collagen as the typical collagen)

A
  • fibrous protein
  • provides tensile strength
  • resist stretching
  • 3 chains wound around each other in a triple helix - assemble into ordered polymers to form collagen fibrils (fibrils can pack tgt into collagen dibers)
56
Q

collagen is secreted as procollagen by _______ (2 answer)

A

fibroblasts (skin, tendon, other connective tissue), osteoblasts (bone)

57
Q

once procollagen is secreted, it is processed into ________, which is assembled into large structures called

A

collagen, collagen fibrils

58
Q

what are the purposes of the extensions on the end of procollagen in a secretory vesicle

A

prevents assembly from inside the cell

59
Q

what cleaves procollagen extensions which then allows it to be become collagen and self assembly into a fibril

A

procollagen proteinase cleaves terminal procollagen extensions

60
Q

connective tissue cells that secrete collagen bind to college in ecm through what (2 answers)

A

integrin (cell surface adhesion receptor) and fibronectin (glycoprotein)

61
Q

differentiate between how fibronectin and integrin conduct their binding

A

fibronectin binds to collagen and integrin on specific binding sites

integrin binds to fibronectin through extracellular domains and binds to adaptor proteins (eg actin filaments) through the intracellular domain

62
Q

state the bond that connects 2 strands of fibronectin

A

disulfide bonds

63
Q

name the responsibilities of elastin in the ecm (connective tissue)

A
  • fibrous protein
  • networks of elastin: gives tissues elasticity, stretch and relax like a rubber band, gives resilience
    other components of ecm: provide strength, prevent tissue from excessive stretching
64
Q

will the basal lamina always be at the base even if epithelial cells come in diff shapes

A

yes - epithelial linings can come in many different shapes and sizes - and the basal lamina will always be at the base (if the epithelial is many layers then the basal lamina will be at the bottom of the layers)

65
Q

ecm is secreted by _______ ______ and influences _______

A

ecm is secreted by epithelial cells and influences cell polarity

66
Q

what is the thickness of the basal lamina (epithelial tissue ecm)

A

very thin, 40-120 nm

67
Q

state the roles of the basal lamina and its implications

A

separates epithelia from underlying tissue, prevent fibroblasts in underlying connective tissue from interacting with epithelial cells yet allows passage of macrophages and lymphocytes

68
Q

the basal lamina is:
the attachment site for ________
anchored by __________
organized by _________

A

the attachment site for epithelia
anchored by hemidesmosomes
organized by laminin

69
Q

laminin (glycoprotein) links integrin (transmembrane adhesion protein) to what

A

links integrin to type IV collagen (fibrous protein)

70
Q

hemidesmosomes anchor epithelial cells to where

A

bassal lamina

71
Q

integrins interact with which glycoprotein to organize the basal lamina

A

laminin

72
Q

explain the components of the plant cell wall (+ their contribution to function)

A
  • main components are cellulose and pectin
  • cellulose microfibrils provide tensile strength
  • pectin fills space and provides resistant to compression
  • also has microtubules attached to the plasma membrane
73
Q

describe the roles and structure of the plant cell wall

A
  • supportive matrix of the plant cell
  • plant cells synthesize cellulose chains at plasma membrane (cellulose synthase complex) and the other cell wall components are synthesized in the golgi and exported by exocytosis
  • when synthesizing, cellulose microfibrils are being added to preexisting wall
74
Q

is the plant cell wall or ecm of animal cells more rigid

A

the plant cell wall

BIO130 (12 decks)

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