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Cell Biology > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is the cytoskeleton?

A

Network of protein filaments throughout cytoplasm

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2
Q

What are the functions of the cytoskeleton?

A 
Mitosis + Cytokinesis
Traffic 
Support 
Cell shape 
Muscle contraction
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3
Q

What are the 3 types of cytoskeleton filament?

A

Intermediate filaments
Microtubules
Actin filaments

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4
Q

What to intermediate filaments do?

Where are they abundant?

A

Provide tensile strength

Cells subject to mechanical stress e.g. muscle cells

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5
Q

What are the 3 main classes of intermediate filaments?

A

Keratin filaments
- epithelial cells

Vimentin filaments
- connective tissue cells, muscle cells + supporting cells

Neurofilaments
- nerve cells

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6
Q

What are nuclear lamins?

A

Intermediate filaments found just under nucleus membrane

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7
Q

What are intermediate filaments made of?

A

Monomers with a central rod domain + globular region at either end

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8
Q

Describe the construction of an intermediate filament

A
  1. Monomers dimerise
  2. 2 dimers line up to form a staggered tetramer
    (N terminus near C terminus of other dimer)
  3. Tetramers pack together end to end
  4. 8 tetramers twisted into a rope
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9
Q

How do keratins connect neighbouring cells?

A

Indirectly connected to filaments of other cells through desmosomes (cell-cell junctions)

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10
Q

How do keratins indirectly connect cells via desmosomes?

A

Cadherins span the 2 membranes

-> bind the 2 cells together

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11
Q

Give an example of an intermediate filament disorder

A

Epidermolysis bullosa simplex

= keratin cannot form normal filaments in the epidermis
-> skin v susceptible to injury

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12
Q

What is the difference between lamins + laminins?

A

Lamins = cytoskeleton proteins

Laminins = ECM proteins

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13
Q

Why are intermediate filaments v stable, strong + durable?

A

Extensive protein-protein contacts

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14
Q

Describe actin filaments

A

In all eukaryotic cells

Made up of globular monomers that associate head to tail

Unstable w/out associated proteins

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15
Q

When do F-actin filaments form?

A

Spontaneously from G-actin above the critical conc

In the presence of ATP, Mg + K

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16
Q

Describe the polymerisation of actin

A
  1. Actin monotoners in cytosol carry ATP
  2. ATP hydrolysed -> ADP after monomers assemble into filament
  3. ADP replaced with ATP when actin disassembles from filament
17
Q

Which proteins bind to actin to modify its properties?

A 
Monomer binding proteins
Nucleating "
Cross-linking "
Capping "
Bundling "
Motor "
18
Q

What are 2 drugs that act on the actin cytoskeleton?

A

Cytochalasin D

  • binds to +ve end of F-actin
  • > prevents further addition of G-actin

Phalloidin binds F-actin + prevents actin filaments from depolymerising

19
Q

What are the 4 functions of actin?

A

> Mechanical strength + cell shape
Cell crawling
Muscle contraction
Organelle movement

20
Q

What is cortical actin?

A

Actin filaments concentrated in a layer in the cortex

- linked into a meshwork by actin binding proteins

21
Q

What is cell crawling?

A

Filopodia or lammelipodia extend a region of plasma membrane
(driven by actin cytoskeleton rearrangement)

Integrins adhere to ECM

Cells use internal contractions to pull itself forward

22
Q

Which family of proteins do actin dependent motor proteins belong to?

A

Myosin family

23
Q

How does mysosin move along actin filaments?

A

Myosin binds + hydrolyses ATP
-> provides energy
= moves from - to + end

24
Q

Describe microtubules

A

Long, hollow cylinders made of tubulin

Most rigid + straight type of filament

25
Q

How are microtubules assembled?

A

From tubulin made up of a dimer of alpha + beta tubulin

26
Q

What maintains microtubules?

A

Balance between assembly + disassembly:

Cell contains mix of microtubules + free tubulin

Microtubules = unstable = undergo rapid remodelling

27
Q

Where do microtubules grow out from?

A

Centrosomes

microtubule organising centre

28
Q

What controls the growth of microtubules?

A

GTP hydrolysis

29
Q

What controls the growth of microtubules?

A

GTP hydrolysis

If new subunits (which have GTP bound to beta tubuilin) are added quicker than beta tubules hydrolyse GTP
-> GTP cap forms
= growth

GTP hydrolysis faster
-> GTP cap lost
= shrinkage

30
Q

How are microtubules stabilised?

A

By probing the environment in search of interacting proteins

31
Q

What are the 3 functions of microtubules?

A

> Cellular organisation, movement of organelles + cell polarity

> Cell division

> Cilia + flagella

32
Q

What are the motor proteins associated with microtubules?

A

Kinesins

Dynesins

33
Q

What do kinesins and dynesins have in common?

A

Both have 2 ATP binding heads + a tail
Both have ATPase activity

Kinesins move towards +ve end
Dynesins move towards -ve end

34
Q

What enables motor proteins to move along microtubules?

What does the tail attach to?

A

ATP hydrolysis provides energy for conformation changes in the head

-> cycle of binding, release + re-binding

Cargo

35
Q

How do microtubules organise cells?

A

ER pulled outwards along microtubules by kinesins

Golgi apparatus pulled in other direction by dyneins

36
Q

What are 2 drugs that interfere with microtubule assembly?

What affect do both of these drugs have?

A

Colchicine - binds free tubulin + prevents polymerisation into microtubules

Taxol - binds to microtubules + prevents them losing subunits

Both are anti-mitotic

37
Q

What do cilia and flagella contain?

A

Stable microtubules that’s moved by dynein

38
Q

How do cilia move?

A

Repetitive cycle of power stroke then recovery stroke

Bending is driven by Dynein

39
Q

Why do cilia + flagella bend?

A

Nexin links are stable

-> walking of dynein along microtubule causes bending rather than sliding

Cell Biology (23 decks)

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