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Fundamentals of Science I > The Cytoskeleton > Flashcards

The Cytoskeleton Flashcards

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1
Q

What is the function of the cytoskeleton?

A

Keep its shape and modify it in response to environmental cues.

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2
Q

What is the cytoskeleton made of?

A
  • Microtubules
  • Intermediate Filaments
  • Actin Filaments
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3
Q

What is the function of microtubules?

A

Organelle Positioning

Intracellular Transport

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4
Q

What is the function of intermediate filaments?

A

Mechanical Strength

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5
Q

What is the function of actin filaments?

A

Cell Shape
Organelle Shape
Cell Migration

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6
Q

How are polymers of the cytoskeleton formed?

A

Monomers join together.

However, it is NOT covalently linked.

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7
Q

What does accessory proteins regulate?

A
  • Site / Rate of filament formation.
  • Polymerization / Depolymerization.
  • Function
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8
Q

What is the cytoskeleton described as being?

A

Dynamic = because it can regulate itself really well and can change its structure really well.

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9
Q

What are cytoskeleton binding polymers?

A

Group of proteins which control everything.

= Binds to specific parts of the cytoskeleton.

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10
Q

What are microfilaments made of?

A

Helical Polymers made of actin and is flexible.

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11
Q

What are intermediate filaments made of?

A

Heterogenous Group of filamentous proteins which has a rope like structure.

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12
Q

What are microtubules made of?

A

Made of hollow tubes known as tubulin.

= Rigid / Long Structure.

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13
Q

What is the structure of actin filaments?

A

Twisted chains of G - Actin and F - Actin.

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14
Q

What are the 3 isoforms of G - Actin and where are they found?

A

Alpha Actin = Muscle Cells
Beta Actin = Non - Muscle Cells
Gamma Actin = Non - Muscle Cells

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15
Q

What does actin filaments present?

A

Structural Polarity.

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16
Q

What determines the length of a filament?

A
  • Concentration of G- Actin.

- Presence of Actin - Binding Proteins.

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17
Q

How can actin filaments (f - actin) grow in length?

A

With G - Actin monomers being added on at either end.

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18
Q

How are G - Actin Levels controlled?

A

Profilin = Facilitates Actin Polymerisation.

Thymosin B - 4 = Prevents addition of actin monomers to F - actin.

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19
Q

What is Actin - Bundling Proteins?

A

Keeps F - Actin in parallel bundles.

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20
Q

What is Cross - Linking Proteins?

A

Maintains F - Actin in gel - like meshwork.

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21
Q

What is F - Actin Severing Proteins?

A

Breaks F - Actin into smaller filaments.

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22
Q

What is a motor protein?

A

Transport of vesicles and / or organelles through actin filaments.

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23
Q

How do actin filaments work in the skeletal muscle?

A

Interaction with myosin allows muscle contraction.

24
Q

What are the 4 types of non - muscle cells?

What is the function of each of theses?

A

Microvilli = wafts bacteria / unidentified objects.
Contractile Bundles = Allows contraction of cells.
Lamellipodia Filopodia = Helps cells to move around.
Contractile Ring = Cells need to divide.
The bundle of actin / myosin allows the final step of cytokinesis to occur.
Therefore, the cell splits into two.

25
Q

What does the cell cortex do?

A

Form a thin sheath beneath the plasma membrane.

26
Q

What process is the actin - myosin ring involved in?

A

Cytokinesis.

HELPS THE CELL TO SPLIT INTO 2

27
Q

Explain the procedure of cell migration.

A

Cell pushes out protrusions (lamellipodia filopodia) = Actin Polymerisation.
The protusions adhere to the surface.
Integrins (link the actin filaments to the extracellular matrix surrounding the cell).
Cell contraction and retraction of the rear part of the cell.

28
Q

How do intermediate filaments form a network?

A

Throughout the cytoplasm, joining upto the cell - cell junctions and the surrounding nucleus.
Known as desmosomes

29
Q

What is the size of intermediate filaments?

A

8 -12 nm.

30
Q

What is the structure of intermediate filaments?

A

Ropelike with many long strands twisted together in order to make different subunits.

31
Q

What is each unit of intermediate filaments made of?

A

1) N - terminal globular head.
2) C - terminal globular tail.
3) Central elongated rod - like domain.

32
Q

What do the intermediate filaments combine in order to form?

A

Units form stable dimers.

33
Q

What do the 2 dimers combine in order to form?

A

Combine in order to form a tetrameter.

34
Q

What is the structure of a rope-like filament?

A

8 tetramers

which is essentially 16 dimers.

35
Q

What are the two main categories of intermediate filaments?

A
  • Cytoplasmic

- Nuclear

36
Q

What are the substances within the cytoplasmic intermediate filaments and where are they found?

A

Keratins = Epithelia
Vimentin and Vimentin - related = Connective Tissue / Muscle Cells / Neurological Cells.
Neurofilaments = Nerve Cells.

37
Q

What are the substances within the nuclear filaments and where are they found?

A

Nuclear Lamins = All nucleated cells.

38
Q

What is an intermediate filaments binding protein?

A

Mainly linkers of IF structures.

They stabilise `and reinforce infilaments into 3D networks.

39
Q

What are 3 examples of intermediate filaments binding proteins?

A

Fillagrin = Binds keratin filaments into bundles.
Synamin and Plectin = binds to desmin and vimentin.
Plakins = Keep the contact between desmosomes of epithelial cells.

40
Q

What is the function of intermediate filaments in the cytoplasm?

A

Tensile Strength = Enables the cells to withstand mechanical stress (to stretch!).

41
Q

How is structural support created by?

A
  • Creates deformable 3D structural framework.

- Reinforces cell shape and fixes organelle localisation.

42
Q

What happens when the tensile strength is removed?

A

The structure of intermediate filaments breaks.

43
Q

Where are the intermediate filaments in the nucleus found?

A

Present in ALL nucleated eukaryotic cells.

44
Q

What kind of structure is formed from intermediate filaments?

A

Mesh structure.

45
Q

What is the structure of microtubules?

A

Hollow tubes made up from protein TUBULIN.

46
Q

What is the name of the main micro - organisation centre of the tubules?

A

Gamma - Tubulin.

47
Q

What is the microtubule organising centre (MTOC)?

A

Specialized protein complexes from where assembly of tubulin starts.

48
Q

What is the most common MTOC?

A

Centrosome

contains y - tubulin ring which initiates the microtubule growth

49
Q

What is the function of microtubules?

A
  • Intracellular Transport.

- Organises position of organelles.

50
Q

What are the two protein molecules?

A 
Dynein = Moves cargo towards the minus ends of the microtubules  
Kinesin = Moves cargo towards the plus ends of the microtubules
51
Q

Where does the microtubules work the hardest?

A

Rhytmic beating of cilia and flagella.

52
Q

Describe the structure of a axoneme.

A

9 pairs of microtubules around 2 central microtubule.

53
Q

What does dynein drive?

A

Bending of cilia and flagella.

54
Q

What controls the assembly of axoneme?

A

Basal body at the base of the tubule.

55
Q

What are the rapid changes in cell shape associated with?

A

Dynamic Cytoskeleton.

Fundamentals of Science I (45 decks)

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