The cytoskeleton Flashcards

1
Q

what is the function of a skeleton?

A

function- allows the cell to keep its shape and modifies the shape due a response to environmental cues. Also controls intracellular movement of organelles

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2
Q

what are the general features of a cytoskeleton?

A

The cytoskeleton is a complex network made of 3 different polymers:

-microtubules
-intermediate filaments
-actin filaments.

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3
Q

What is the function of the polymer microtubules?

A

microtubules:
-organelle positioning
-intracellular transport

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4
Q

what is the function of the polymer intermediate filaments

A

intermediate filaments:
-mechanical strength

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5
Q

what is the function of actin filaments?

A

actin filaments:
-cell shape
-organelle shape
-cell migration

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6
Q

definition of accessory proteins

A

accessory proteins- assist in the function of other proteins

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7
Q

what do accessory proteins regulate?

A

accessory proteins regulate:
-site and rate of filament formation
-polymerisation/depolymerisation
-function

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8
Q

what is the structure and function of microfilaments/actin filaments?

A

Structure:
-helical polymers made of ACTIN
-flexible, organised into 2D networks and 3D gels

Function:
-cell shape
-organelle shape
-cell migration

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9
Q

what is the structure and function of intermediate filaments?

A

structure:
-heterogenous group of filamentous proteins (different types of proteins that forms filaments)
-rope like structure

function:
-gives mechanical strength to the cell

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10
Q

what is the structure and function of microtubules?

A

structure:
-hollow tubes made of TUBULIN
-rigid, long straight

function:
-organelle positioning
-intracellular transport
-cell movement

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11
Q

what is the structure of Actin filaments?

A

Actin filaments:
-twisted chains of monomers of the protein actin (G-actin) this chaoin constitutes the filamentous form of F-actin
-thinnest class of cytoskeleton filaments
-presents structural polarity
-associated with a large number of actin binding proteins

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12
Q

How are F-actin filaments formed?

A

F-actin can grow by addition of actin monomers (G-actin) at either end

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13
Q

what is the length o the filament determined by?

A

The length of the filament is determined by:
-concentration of G-actin
-presence of Actin Binding proteins

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14
Q

What are G-actin levels controlled by?

A

G-actin levels are controlled mainly by 2 ABPs:

-Profillin- facilitates actin polymerization
-Thymosin b4- prevents the addition of actin monomers to F-actin

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15
Q

What is the role of Actin Bundling proteins and Cross-linking proteins?

A

Actin Bundling Proteins- Keeps F-actin in parallel bundles (as the microvilli observed in epithelial cells)

Cross linking proteins- maintains F-actin in a gel like meshwork

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16
Q

What is the role of F-actin severing proteins and Motor proteins (Myosin)?

A

F-actin severing proteins:
-break F-actin into smaller filaments

Motor proteins (Myosin):
-transport of vesicles and/or organelles through actin filaments

17
Q

Describe the structure and function of skeletal muscle?

A

structure:
-arranged in a para-crystalline array integrated with different ABPs

function- interaction with myosin motors allow muscles to contract

18
Q

describe the structure of non muscle cells

A

structure:
-cell cortex: forms thin sheath beneath the plasma membrane
-associated with myosin to form a purse string ring.

19
Q

explain cell migration in the actin filaments

A

-the cell pushes out protrustions at its front.
-actin polymerisation
-these protrustions adhere to the surface
-integrins (link the actin filaments to the extracellular matrix)

20
Q

describe the structure of intermediate filaments (IF) ?

A

intermediate filaments:
-toughest of the cytoskeleton filaments
-ropelike with many long strands twisted together
-intermediate size (8-12nm)
-forms a network

21
Q

what is each unit of immediate filaments made of?

A

each unit is made of:
-N-terminal globular head
-C-terminal globular tail
-Central elongated rod-like domain

22
Q

What are 2 types of intermediate filaments?

A

1) Cytoplasmic
2) nuclear

23
Q

what does a nuclear intermediate filament form?

A

nuclear intermediate filaments:

-nucleur lamins in all nucleated cells

23
Q

what do cytoplasmic intermediate filaments form?

A

cytoplasmic intermediate filaments form:

-keratins in epithelia
-vimentin and vimentin-related in connective tissue, muscle cells and neuroglial cells
-neurofilaments in nerve cells

24
explain the role of intermediate filaments binding proteins (IFBP)
IFBP stabilizes and reinforces IF into 3D networks
25
list examples of IFBP
Examples IFBP: -Fillagrin: binds keratin filaments into bundles -Synamin and Plectin: binds desmin and vimentin -link IF to the other cytoskeleton compounds Plakins:
26
what is the function of the IF in the cytoplasm?
IF- tensile strength: this enables the cell to withstand mechanical stress so they can stretch
27
what are the functions of the intermediate filaments in the nucleus?
functions of intermediate filaments in the nucleus: -present in all nucleated eukaryotic cells -forms mesh rather than rope-like structure -line in the inner face of nuclear envelope allows it to strengthen and provide attachment sites for chromatin -disassemble and reform at each cell division as nuclear envelope
28
what is the structure of microtubules?
structure of microtubules: -hollow tubes made up of the protein tubulin -relatively stiff (25nm) -each filament is polarised -assemble/disassemble in response to the cells needs
29
definition of microtubule organising centre (MTOC)
MTOC- specialised protein complexes from where the assembly of tubulin starts
30
what are the functions of microtubules?
INTRACELLULAR TRANSPORT: -act like railway tracks on which molecular motors run -different motors for different cargoes -directionality of filaments is vital ORGANISES POSITION OF ORGANELLES: -provides polarisation of cells -directionality of filaments is vital