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BMS100 test 1 > Plasma membrane and signaling > Flashcards

Plasma membrane and signaling Flashcards

1
Q

what are some extracellular signals the plasma membrane responds to? what do extracellular signal need?

A

-plasma membrane respond to many extracellular signals
–> growth factors and anti growth factors
–> signals that change cell activity (hormones, neurotransmitters)

extracellular signals need a receptor expressed to respond to the signal (hormone)

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2
Q

what 3 domains do most receptors have?

A
  1. hydrophobic domains: that extend through the lipid bilayer (i.e. alpha helix)
  2. extracellular domain: that binds the the message (i.e. hormones)
  3. intracellular domain: that amplifies signal
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3
Q

what do most signals involve?

A

most signals involve binding of chemical (signal) to a high-affinity protein receptor on the cell membrane –> a signal that’s propagated into the cytosol

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4
Q

water soluble hormone signalling pathway

A
  1. water soluble hormones are membrane insoluble. they bind to membrane receptors
  2. the binding activates G protein
  3. the activated G protein activates adenylyl cyclase
  4. adenylyl cyclase catalyses the conversion of ATP to cAMP, the secondary messenger in this pathway
  5. cAMP activates protein kinases
  6. protein kinases phosphorylate proteins in the cytoplasm. this activated these proteins, allowing them to alter cell activity.
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5
Q

what do membrane proteins do?

A

link cell membrane to cytoskeleton or to extracellular structure (ECM, other cells) and junctions

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6
Q

cell-cell junctions vs. cell-matrix junctions

A

cell-cell junctions: (from most apical to basal)
tight junctions
adherens junctions
desmosomes
gap junctions

cell-matrix junctions:
hemidesmosomes
actin-linked cell matrix junctions

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7
Q

cytoskeleton

A

microtubules
microfilaments
intermediate filaments

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8
Q

extracellular structures

A

tight junctions
desmosomes
hemidesmosomes
adherens junctions

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9
Q

tight junctions

A

-seperate apical from basal
-selective and “leak proof” or less selection
-regulates movement across membranes and other epithelial cells

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10
Q

anchoring junction- desmosomes

A

-intracellular component: plaque formed of molecules that are associated with cadherins
–> intermediate filaments (cytoskeleton) bind plaques

-extracellular component: cadherins on 1 cell interact with cadherins on neighbouring cells

-structural integrity for a wide range of cells and tissues

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11
Q

anchoring junction- hemidesmosomes

A

-similar to desmosomes, but extracellular components involves integrin proteins
–> plaque still binds to intermediate filaments

-the integrin commonly binds the basement membrane/ basolateral
-how epithelial cells stay anchored to basements membrane and underlying connective tissue

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12
Q

what protein and cytoskeleton component are part of desmosomes?

A

cadherins and intermediate filament

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13
Q

what protein and cytoskeleton component are part of hemidesmosomes?

A

intern and intermediate filament

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14
Q

anchoring junction- adherens junction

A

-have plaque to connect to:
–> another cell: cadherins
–>basement membrane: integrins
-connect with microfilaments formed from actin (cytoskeleton)

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15
Q

what protein and cytoskeleton component are part of adherens junctions?

A

cadherins (connect to other cell)
integrins (connect to basement membrane)
-microfilaments

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16
Q

functions of the cytoskeleton

A

-cellular movement: move through space (i.e. fibroblast) or perform work and change shape (i.e. muscle cell)

-organize cell components/organelles: mitosis, meiosis, shuttle organelles and residues

-cell structure: strength (skin), shape (absorptive surfaces)

-communication: intracellular signals to regulate growth

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17
Q

microtubules function and molecule

A

-traffic organelles and cell division
-organization of overall cell structure
-cell movement
–>tubulin

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18
Q

microfilaments function and molecule

A

-cell movement
-structural organization of plasma membrane
–> actin

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19
Q

intermediate filaments function and molecules

A

-overall structural integrity of the cell
–> keratins and desmin

20
Q

3 characteristics of cytoskeleton

A
  1. dynamic: filament subunits (monomers, heterodimers) build themselves into polymer strands –> once monomers reach critical [ ] and interact with nucleating factors –> polymer forms
  2. tightly regulated: filament assembly and disassembly –> intracellular signals
    -govern structure and formation of polymers
  3. generate force: proteins interact with strands of cytoskeleton;
    -move cell or organelles along the axis of the strands
    -generate power or motion in cells through contraction
21
Q

microfilaments- actin

A

-monomer: G actin
-polymer: F actin
-nucleating factors stimulate formation of F-actin:
–> formin: linear arrangements
–> ARP 2/3 complex: mesh like nets

-when F-actin is formed, it spontaneously degrades
-each G-actin has ATP bound
-over time G-actin hydrolyzes ATP to ADP, which makes it more likely that it will “fall off” the F actin strand

-F-actin stability depends on a number of factors:
–>[ ] of G-actin
–>”caps” that can be applied to F-actin that prevent disassembly (tropomodulin- capping protein)
–>proteins that increase or decrease rate G-actin hydrolyzes ATP
–>nucleating factors or inhibitory factors that modify the formation of F-actin (i.e. formin, ARP2/3)

-mucsle cell: stable, parallel actin fibres, generate force, strong anchor

-fibroblast: “crawl” to deposit collagen/ ECM; meshes, fibres, filopodium

-use myosin as motor

22
Q

microtubules

A

-protein monomer= tubulin
-alpha and beta= form dimers
-alpha beta dimers organize into helical tube
-positive end= alpha
-negative end = beta
–> polarity

-beta monomers hydrolyze a nucleotide triphosphate –> cleave GTP to GDP and Pi

-after GTP cleaved, dimer “falls off” microtubule= dynamic instabilty

-microtubule organizing centre (MTOC):
-made of 2 centrioles that form the centrosomes
-centrioles made of microtubules –> tubulin triplet (9x3)
-microtubules radiate off MTOC –> cellular scaffoling
-put cell structures at specific spots
-determine cell polarity (i.e. lumen vs basement membrane)

-cellular movement: rotate and move in whip like fashion
–> cilia: sperm cells
–> flagella: respiratory mucosa

-cell divide; MTOC splits and pulls chromosomes to new daughter cells

-singalling: the primary cilium; senses important stimuli in extracellular environment to help with cell localization or function

-use kinesins and dynes and motors

23
Q

microfilaments, microtubules and cellular motors (which proteins do they use)

what do molecule motors use for energy?

A

-f-actin and microtubules form a network of dynamic filaments that “molecular motors” can move along (i.e. train tracks)
-f-actin: myosin protein- “walk” along microfilaments= cell contract

-microtubules: dynein and kinesin proteins walk along microtubules and cause “whipping” of cilia and flagella
-dyneiens and kinesins move in opposite directions along microtubules

–> molecular motors use ATP to move

24
Q

intermediate filaments

A

-stability
-long proteins with alpha helix confirmation that coils round other monomers to form dimers coil (“coiled-coil”)
-more stable than actin and tubulin –> dont hydrolyze GTAP or ATP so dont dissociate easily
i.e. lamina, keratins, vimetins (desmin), neurofilaments

alpha helical monomer –> coiled-coil dimer –> staggered tetramer of 2 coiled-coil dimers –> lateral association of 8 tetramers

25
Q

types of intermediate filaments

A

lamins: a network of filaments just under the nuclear membrane

keratins: epithelial cells, hair, nails; strong, modified to limit water permeability

neurofilaments: intermediate filaments found around neurons

vimentin family (vimentin, desmin, GFAP): confer stability and structure to;
-many mesenchymal cells
-muscle cells, some epithelial cells
-glial cells (brain cell)

26
Q

cytoskeleton in an idealized epithelial cells

A

-actin filaments for shape of microvilli
-desmins for strength across cell (intermediate filaments)
-microtubule + and - end for polarity of cell

27
Q

what is the difference between hemidesmosomes and desmosomes and what is the similarity?

A

desmosomes form intracellular plaque with cadherins

hemidesmosomes form intracellular plauque with integrins

both plaques still bind with intermediate filaments

28
Q

tight junctions vs desmosomes vs hemidesmosomes vs adherns junctions proteins/plaque

A

tight junctions: none
desmosomes: cadherins
hemidesmosomes: integrins
adherns junctions: cadherins and integrins

29
Q

tight junctions vs desmosomes vs hemidesmosomes vs adherns junctions cytoskleton connection

A

tight junctions: none
desmosomes: intermediate filaments
hemidesmosomes: intermediate filaments
adherns junctions: microfilaments

30
Q

compare the different molecules used in: microtubules, microfilaments and intermediate filaments

A

microtubules: tubulin

microfilaments: actin

intermediate filaments: keratins, desmin

31
Q

which cytoskeletal structures (microtubules, microfilaments and intermediate filaments) help with cell movement (AKA cellular motors)?

A

microtubules and microfilaments

32
Q

where can you find intermediate filaments, microtubules and actin filaments

A

intermediate filaments- all throughout cell

microtubules: going up and down with + and - end

actin microfilaments: along borders and in microvilli for movement

33
Q

what structure do intermediate filaments form?

A

alpha helix –> coiled-coil dimers

34
Q

what protein in microtubules acts as a cellular motor?

A

dyneins and kinesins

35
Q

what protein in microfilaments acts as a cellular motor?

A

myosin

36
Q

what nucleating factors stimulate the formation of F-actin in microfilaments

A

formin (linear) and ARP 2/3 complex (mesh like nets)

37
Q

what types of cells are microfilaments found in?

A

muscle cells - parallel actin fibres, generate force

fibroblasts - filopodium “crawl”, meshes of actin fibres

38
Q

what is a capping protein that can be applied to F-actin on microfilaments to prevent its disassembly?

A

“caps” that can be applied to F-actin that prevent disassembly (tropomodulin- capping protein)

39
Q

what do G-actin hydrolyze to become F-actin?

A

ATP

40
Q

what makes up microtubules?

A

alpha beta tubulin dimers

41
Q

what do beta monomers on microtubules hydrolyze?

A

GTP

42
Q

+ and - end on microtubules

A

+ end= alpha
- end= beta
on tubulin dimers

43
Q

which cytoskeletal structure has polarity/ a positive and negative end?

A

microtubules; alpha beta dimer of tubulin

44
Q

what is it called when a beta monomer cleaves GTP to GDP and Pi on a microtubule

A

dynamic instability

45
Q

what is made of 2 centrioles that forms the centrosome for microtubules

A

microtubule organizing centre (MTOC)

BMS100 test 1 (24 decks)

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