Cytoskeleton Flashcards
What is the cytoskeleton?
A network of filaments providing structural integrity to the cell
The cytoskeleton is used for…
…transportation within the cell
The cytoskeleton allows movement of …
… the cell and cellular projections
What is the cytoskeleton responsible for?
cellular polarity
The cytoskeleton is not always…
…permanent, can be rapidly remodelled even within permanent structures
Protofilaments are made up of …
…smaller subunits
protofilaments are built by…
…repetitive assembly of small soluble proteins
Protofilaments are weak…
…non-covalent interactions between monomers
Polymerisation and depolymerisation can be used to …
…do mechanical work
Distribution and behaviour regulated by …
…associated ‘accessory proteins’
Protofilaments are controlled by…
…extracellular and intracellular signals
Filaments are made of …
…protofilaments
Lateral bonds between protofilaments hold …
…filaments together
Arrangement depends on …
…the filament type
The eukaryotic cytoskeleton has …
…three major components
The eukaryotic cytoskeleton has three major components which are:
Microfilaments
Microtubules
Intermediate filaments
What colour are microfilaments?
Red
What colour are Microtubules?
Green
Narrowest type of microfilament?
7nm diameter
Microfilaments are …
…Actin monomers (G-actin), globular polypeptide
Microfilaments are polymers of…
…F-actin
Microfilaments are ATP/ADP…
…binding sites
How do microfilaments assemble?
Assemble head to tail, giving polarity
Two parallel protofilaments in a…
…right-handed helix
Microfilaments are crosslinked by …
…accessory proteins to form bundles, or networks
Polymerisation of microfilaments initiated by …
…actin related proteins (ARP)
Plus end of microfilaments gains more …
…monomers than it loses
Minus end of microfilaments loses …
…more monomers than it gains
Microfilaments have a […] structure, known as […]
Microfilaments have a DYNAMIC structure, known as TREADMILLING
ARPs found at …
…end of actin polymers, and can bind to side of other fibres, creating a web.
Examples of parallel bundles of microfilaments?
Microvilli
Muscle
Examples of mesh of microfilaments?
Lamellepodia
Actin-myosin interactions cause…
…contraction of the ring, resulting in separation of daughter cells.
Villi and Fibrin link …
…the actin fibres into tight bundles of 20-30 fibres
Myosin I connects…
… the actin to the plasma membrane
What is attached to the end of microfilaments?
A cap of proteins is attached to the end of microfilaments.
Actin microfilaments run…
…the entire length and support each microvillus
Cross linking actin-binding proteins link…
…microfilaments to eachother and to the plasma membrane
Pathogen is detected by …
…surface receptors.
Signals are transmitted into…
…the cell to modify actin arrangement.
Cell moves towards location of …
…strongest signal, up a concentration gradient (chemotaxis).
What are microtubules made from?
Made from α-tubulin, β-tubulin heterodimer subunits
Microtubules involve…
…GTP/GDP binding.
HOw many protofilaments in microtubules?
13
Different types of interactions in microtubules?
Longitudinal α-β interactions
Lateral α-α and β-β interactions
Structure of microtubules?
Very stiff and straight
What is required in microtubules to start polymerisation?
nucleation
GTP bound dimers added to …
… + end
GTP hydrolysed in …
…polymer
GTP hydrolysis of terminal dimers causes a …
…change in shape of protofilaments -catastrophe
Microtubules are insulated by…
…γ-tubulin at - end
Wheres the microtubule-organising centre located on animal cells?
in centrosome in animal cells
How do microtubules grow?
Grow outwards, from centre of cell
Microtubules are used to do what?
Used to organise position of organelles
Microtubules can determine…
…cellular polarity eg. Epithelial cells centrosome is near apical membrane
Three types of microtubule involved in mitosis:
Aster microtubules
Polar microtubules
Kinetocore microtubules
Whats the red layer in microtubules?
flagella
Whats the blue layer in microtubules?
movement
Function of intermediate filaments?
- Mechanical stability
- Provide mechanical resistance to external stresses, eg erythrocyte deformation
The type of intermediate filament depends on…
…location
Intermediate filaments are not found in all cell types or all animals, only in…
…‘squishy’ animals.
Intermediate filaments details:
- α helix, forms parallel dimer, then staggered antiparallel tetramer
- Many disulphide bridges between cysteine molecules
- No nucleoside binding
- No polarity
- Rope-like
- Tough, form protective covering
How many classes of intermediate filament proteins?
1) Keratin
2) Vimentin and vimentin-related
3) Neurofilaments
4) Nuclear lamins
Function of keratins?
Organelle positioning, cell shape, and integrity
Function of vimentin and vimentin related and neurofilaments?
Regulate axon diameter, and axon growth
Function of nuclear lamins?
Structural function and transcription regulation
Where are keratins found?
in epithelia
Where are vimentin and vimentin related found?
in connective tissue, muscle cells, and neurological cells.
Where are neurofilaments found?
in nerve cells.
Where are nuclear lamins found?
in all animal cells.
Keratin intermediate filaments strengthen …
… the epithelium
Keratin attach to…
…desmosomes and hemidesmosomes
α-Keratin based intermediate filaments form …
…protective coverings on mammals
The cytoskeleton allows cells to …
- move
- divide
The cytoskeleton maintains…
…cell shape and intracellular organisation
Cytoskeleton provides…
…mechanical strength
Cytoskeleton acts as a…
…intracellular road network, for transport within the cell
Myosins- At least 18 types, almost all …
…move towards + end
How many types of myosin?
18
Myosin II involved in …
…muscle contraction
Myosin V involved in…
…vesicle/organelle transport
Myosin I anchors…
…actin bundles to membrane in microvilli
How many families of kinesins?
at least 14 families
kinesins move towards…
… + end
Kinesins carry…
…membrane enclosed organelles or bind other microtubules
Dyenins move towards…
… - end
Dyenins are the…
…fastest
Function of Cytoplasmic dyenin?
vesicle trafficking and golgi localisation
Axonemal dyenins drive…
…movement of cilia and flegella
ATP is hydrolysed to…
…ATP is hydrolysed to
ADP disassociates from …
…head
In the Prokaryotic cytoskeleton, homologues of all three components found in ….
…bacteria
In the Prokaryotic cytoskeleton, FtsZ polymerises into…
…ring
In the Prokaryotic cytoskeleton, MreB (and Mbl) serve as…
…scaffold for cell wall synthesis
In the Prokaryotic cytoskeleton, there are no…
…molecular motors
No molecular motors is thought to…
… limit cellular complexity and size