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VP Exam 2 > Cell bio- cytoskeleton > Flashcards

Cell bio- cytoskeleton Flashcards

1
Q

What are the three components of a cytoskeleton

A

actin filaments
microtubules
intermediate filaments

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2
Q

actin filaments

A

determine the shape of a cell and are necessary for locomotion

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3
Q

mictotubules

A

determine the positions of membrane-enclosed organelles, direct intracellular transport and form mitotic spindle

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4
Q

intermediate filaments

A

provide mechanical strength

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5
Q

microtubules structure

A

hollow. polymer of the protein tubulin= heterodimer of alfa-tubulin and beta-tubulin

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6
Q

alfa-tubulin

A

GTP molecule that is trapped and never hydrolyzed

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7
Q

beta-tubulin

A

GTP bound that is exchangeable with GDP

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8
Q

dynamic instability

A

process of microtubules to grow and shrink.

influenced by the binding and hydrolysis of GTP on the beta-tubilin

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9
Q

Microtubule organizing center (MTOC)

A

centrosome= origination or microtubules

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10
Q

Microtubule-associated proteins (MAPs)

A

move along microtubules bringing transport vesicles to target organelles in the cell

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11
Q

two types of MAPs

A 
kinesin= travels toward plus end
Dynein= travels toward minus end
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12
Q

Functions of MAPs (2)

A

Move organelles and vesicles in the cell

move vesicles with pigments (melanosomes) in the skin

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13
Q

Flagella

A

used to move cells in a liquid environment

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14
Q

cilia

A

move fluid above a cell

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15
Q

Actin structure

A

2 parallel protofilaments in helix

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16
Q

Actin filaments grow and shrink

A

polymerization of ATP= grow depolymerize= shrink

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17
Q

two forms of actin crosslink

A 
bundle-forming= parallel
gel-forming= weave
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18
Q

actin-associated proteins (3)

A 
Kinsein= moves to plus end
dynein= moves to negative end
myosin= muscle contraction
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19
Q

Sarcomere structure

A

Z-disk= separates sarcomers
Dark band= myosin
Light band= actin filaments

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20
Q

tropomyosin

A

bind to actin to prevent myosin from binding when CA2+ is absent, is removed with Ca2+

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21
Q

Intermediate filament characteristics

A

no polarity, no ATP or GTP, no movement, no motor proteins

associated with cell-cell junctions to strengthen the cells and epithelia

22
Q

intermediate filament structure

A

16 dimers= 32 coiled monomers

23
Q

types of intermediate filament proteins in vertebrate cells (2)

A 
nuclear= Lamina A,B,C
epithelial= Type 1 keratins (acidic), type 2 keratins (basic)
24
Q

majority Intracellualr ions (2)

A

K+

H+

25
Q

majority extracellualr ions (4)

A

Na+
Cl
Mg2+
Ca2+

26
Q

Permeability of lipid bilayer

A

permeable: hydrophobic molecules
semipermeable: small and large uncharged polar molecules
nonpermeable: ions

27
Q

membrane potential

A

the membrane potential of an unstimulated cell= resting

28
Q

electrochemical gradient

A

combination of membrane potential and concentration gradient of the solute

29
Q

7 ways a protein can associate with the plasma membrane

A
  1. single alfa helix
  2. multiple alfa helicies
  3. rolled-up bets sheet (beta barrel)
  4. attached only to one layer (with one hydrophobic face)
  5. attached to the membrane by covalently bound lipid chain
  6. via an oligosaccharide
  7. attached to other proteins (inside or outside the cell)
30
Q

transporter structural features (5)

A

built from 10+ alfa helicies (transmembrane domains)
binding sites are located midway through the membrane
show two different states (inward-open and outward-open conformation)
binding sites are accessible by passageways from only one side of the membrane at one time
could work in reverse direction if ion and solute gradients were adjusted

31
Q

two examples of transmembrane proteins

A 
Na/glucose cotransporter (SGLT)
glucose transporter (GLUT)
32
Q

two main classes of membrane transport proteins

A

channels and transporters (carriers)

33
Q

channels

A

form pores for specific solutes (ions, water, ammonia)

weakly interact with the solute

34
Q

transporters

A

bind the specific substrate (solute) to be transported

undergo a series of conformational changes

35
Q

4 typed of ion channels

A 
voltage-gated (na+ Channel)
ligand-gated extracellular
(nicotinergic receptor)
ligand-gated intracellular
mechanically gated  (inner ear mechanosensitive channel)
36
Q

passive transport

A

transports sown a concentration gradient

occurs spontaneously by diffusion

37
Q

active transport

A

require energy ans ia mediated by transporters

moves solutes against its concentration gradient

38
Q

passive diffusion

A

molecule dissolves in the phospholipid bilayer, diffuses across it, then dissolves in the qa solution at the other side
no membrane proteins are involved
direction is determined by the relative concentration inside and outside the cell
net flow= down concentration gradient: high to low concentraiton

39
Q

facilitated diffusion

A

direction determined by relative concentrations inside and outside the cell
no external source of energy
passage is mediated by proteins that enable the transported molecule to cross the membrane without interacting with hydrophobic interior (allows passage of polar molecules)

40
Q

classification of active transporters (2)

A

direction: uiport, symport, antiport
energy: primary, secondary, tertiary

41
Q

uniporters

A

passive transport of only one molecule

42
Q

symporters

A

coupled transporters of 2 molecules in the same direction (co-transporters)

43
Q

antiporters

A

transport of a second molecule in the opposite direction

44
Q

secondary active transporters

A

driven by a gradient that has been generated by a primary active transporter

45
Q

tertiary active transporters

A

driven by a gradient by a secondary active transporter

46
Q

example of primary active transporter

A

Na+, K+ ATPase
3 na+ molecules exit while 2 k+ molecules enter the cell
use ATP

47
Q

example of secondary active symporter

A

sodium glucose cotransporter (SGLT)
one glucose with 2 Na+ are transported inside the cell
transports glucose against concentration gradient

48
Q

examples of secondary active antiporters (2)

A

sodium/calcium exchanger (NCX) and sodium/proton exchanger (NHE)
transport against CA and H gradient

49
Q

example of tertiary active transporter

A

proton/peptide symporter

50
Q

aquporins

A

specific water channels

for cells that secrete or reabsorb high amounts of water= more efficient

VP Exam 2 (10 decks)

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