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Structure + Function 1 > Cells alive 3- cytoskeleton > Flashcards

Cells alive 3- cytoskeleton Flashcards

1
Q

what are the functions of the cytoskeleton?

A
  • support
  • movement
  • resistance to mechanical forces
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2
Q

what are the 3 types of filaments in a cytoskeleton?

A

-microfilaments
- intermediate filaments
- microtubules

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3
Q

what are the monomers in microfilaments?

A

actin

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4
Q

what size are microfilaments

A

v small: 5-9nm

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5
Q

what are microfilaments made of and how are they assembled?

A

made of globular proteins called actin which assemble into two stranded helical polymers

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6
Q

where do you find microfilaments?

A

they are dispersed through the cell but concentrated beneath the cortex

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7
Q

how are microfilaments distributed?

A

the actin anchors to the mesh proteins in the cortex and distribute like a web

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8
Q

what is the function of microfilaments?

A

cell shape and motility

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9
Q

are microfilaments dynamic?

A

yes

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10
Q

what is the size of intermediate filaments?

A

10nm diameter (hollow tube)

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11
Q

are intermediate filaments more or less dynamic than microfilaments?

A

less

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12
Q

what is the structure of intermediate filaments?

A

extended alpha-helical regions wind together into dimers which then associate into tetramers, these wind together to form rope-like fibres

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13
Q

what is a dimer?

A

2 joined monomers

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14
Q

what is a tetramer

A

4+ subunits

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15
Q

give examples of intermediate filaments

A

keratins in epithelial cells
desmin in muscle cells

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16
Q

what is the function of intermediate filaments?

A

mechanical support of cell structures

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17
Q

what is the size of microtubules?

A

25nm in diameter

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18
Q

what are microtubules made of?

A

globular proteins called tubulin

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19
Q

what is the minimal subunit of microtubules?

A

dimer of alpha beta subunit

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20
Q

how is tubulin formed?

A

alpha and beta tubulin subunits dimerise to form tubulin

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21
Q

what is the structure of microtubules?

A
  • long and straight
  • one end (-) is attached to a microtubule organising centre (MTOC) while the other end (+) grows and shrinks
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22
Q

what protein “walks” along the microtubule

A

motor proteins

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23
Q

are intermediate filament monomers globular?

A

no

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24
Q

typically microtubules are attached to one point within the cell; what is it called?

A

microtubule organising centre

25
Q

true or false…Monomers are added to the filaments of the cytoskeleton by covalent interactions.

A

false

26
Q

within the cytoskeleton what is the concentration at which the rate of monomer addition equals the rate of removal known as?

A

The critical concentration

27
Q

Microtubules and actin filaments have a fast growing and a slow growing end. Name 2 mechanisms by which this is achieved

A
  • conformation change
  • nucleotide hydrolysis
28
Q

Name one toxin or drug which affects the assembly or disassembly of the cytoskeleton.

A

vincristine

29
Q

Which of the following are examples of cytoskeletal motor proteins?
- tublin
- dynein
- actin
- myosin
- kinesin

A
  • dynein
  • myosin
  • kinesin
30
Q

what are the cytoskeletal elements to these motor proteins
- dyneins
- myosins
- kinesins

A

dyneins = microtubules
kinesins = microtubules
myosins = actin filaments

31
Q

Put the following in order:

Myosin head bound to actin filament…

ATP hydrolysed

Myosin head changes shape to move forwards

Phosphate released and mysoin reattaches to actin

Myosin releases actin

ADP released and conformation change (power stroke)

Myosin binds ATP

A
  1. myosin binds ATP
  2. myosin releases actin
  3. ATP hydrolysed
  4. myosin head changes shape to move forwards
  5. phosphate released and myosin reattaches to actin
  6. ADP released and conformation change (power stroke)
32
Q

Name two organelles which are held in position by the actions of motor proteins on microtubules.

A

golgi

endoplasmic reticulum

33
Q

Cytoskeletal elements are central to cell motility. Match the form of motility to the element:

  • flagella and cilia
  • muscle contraction
  • cell crawling
  • microvilli in gut

with

actin filaments
microtubules
intermediate filaments

A

flagella and cilia = microtubules
muscle contraction = actin filaments
cell crawling = actin filaments
microvilli in gut = actin filaments

34
Q

What is the order of the three cytoskeletal elements in order of size? (smallest to largest)

A

microfilaments, intermediate filaments, microtubules

35
Q

What is the main role of microtubules?

A

Organelle positioning and intracellular transport

36
Q

Actin filaments and microtubules have fast growing ends. How is this achieved?

A

nucleotide hydrolysis

37
Q

Myosin, Kinesin, and Dynein are examples of what?

A

motor proteins

38
Q

Motor proteins on microtubules hold the following organelle(s) in position:

ER

Golgi

Chromosome

All of the above

A

all of the above

39
Q

What is vincristine?

A

a chemotherapy drug that inhibits tubulin polymerisation

40
Q

What is the default route taken by a protein once it has completed its journey through the Golgi?

A

constitutive exocytosis

41
Q

How are cells protected from their own lysosomal hydrolases?

A

these enzymes only work within a membrane at a specific pH range

42
Q

What coat does your protein need if it wants to go from the ER to the Golgi?

A

COP II

43
Q

What coat does your protein need if it wants to go from the Golgi to the ER?

A

COP I

44
Q

What coat does your protein need if it wants to go from the plasma membrane to the endosome?

A

Clathrin

45
Q

What is the name of the protein that links clathrin to the cargo receptor?

A

adaptin

46
Q

What is the name of the protein that cleaves off the newly formed vesicle?

A

dynamin

47
Q

What is the process via which certain components can be retrieved from the plasma membrane following exocytosis?

A

endocytosis

48
Q

How is myosin moving along actin filaments related to muscle contraction?

A

When a myosin head pulls against actin the sacromere shortens.

It is chains of sacromeres that form myofibrils which bundle together to form muscle fibres that stretch the length of the muscle cell.

49
Q

How do kinesins move along microtubules?

A

It has two globular heads that interacts with the cytoskeleton.

Kinesin moves from the negative end of the microtubule to the positive.

The globular heads use ATP hydrolysis to power the conformation changes that walk the motors along the microtubules.

Each head attahes and releases itself alternately, like moving one foot then the other.

50
Q

How are kinesins moving related to intracellular transport and organisation?

A

The motor proteins are attached to the organelle or vesicle that they are moving so that as the motor protein moves, so does the organelle.

51
Q

What are the types of cellular motility?

A

Cell crawling

Phagocytosis

Microvilli

52
Q

How are microvilli related to cellular motility?

A

Bundles of actin fibres extend to the tip and there are myosins attached to the cell membrane that ‘walk’ along the actin filaments, causing the microvillus to wave.

53
Q

What is it called when filaments polymerise and depolymerase rapidly?

A

nucleation

54
Q

Explain what nucleation is.

A

Hardest part because bonds between subunits need to be broken.

Occurs in lag phase.

55
Q

What occurs in growth phase?

A

elongation

56
Q

At equilibrium, what is the critical concentration?

How do you work it out?

A

The concentration of monomers free in the cytoplasm after elongation

cc = Koff/Kon

cc is often greater at one end, which elongates faster. If the concentration of free monomers drops then this end also depolymerises fastest. This is the plus end.

57
Q

Give 3 examples of how the cytoskeleton can hold a tissue together?

A

Tight junctions seal epithelial membranes and limit the passage of molecules. They contribute to the maintenance of cell polarity

Anchoring junctions (can attach cells to each other using adherins junctions and desmosomes. They can bind cells to the extracellular matrix using local adhesions and hemi-desmosomes

Gap junctions (directly connect cytoplasm of adjacent cells, hollow junction is made from connexins

58
Q

What type of myosin makes muscles contract?

A

myosin II

59
Q

what motor proteins bind to microtubules and where do they move?

A

kinesin moves from - to +
dynein moves + to -

Structure + Function 1 (18 decks)

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