Cytoskeleton Flashcards
Why do cells need a cytoskeleton
Cells need to be strong and dynamic
Why don’t plant cells move
Because they have a cell wall
What are the 3 core filament proteins in the cytoskeleton
Actin microfilaments
microtubules
Intermediate filaments
What is this a cross section of
Actin microfilament
What is this a cross section of
Microtubule
Around 25nm in diameter
What is this a cross section of
Intermediate filaments
What are the characteristics of actin microfilaments
What are the characteristics of microtubules
What are the characteristics of intermediate filaments
Label this diagram of an actin microfilament
Actin Microfilaments :
Mictrotubules:
Intermediate filaments:
Why are filaments used for strength in a cell
Why are filaments made up of subunits
What is the structure of intermediate filaments and how is its structure formed
What happens if something goes wrong with intermediate filaments
Lead to disease e.g amyotrophic lateral sclerosis
What are the characteristics of the bacterial cytoskeleton
What are some different examples of microfilaments in a cell and what do they do
What are the characteristics of actin
What characteristic does microfilaments have
They are dynamic
What are the phases of dynamic filament
What is the critical concentration
What is nucleation needed for
Neede to facilitate growth
It brings G actin together to form oligomers
Using a diagram, describe the process of treadmilling
What is treadmilling
What happens when ATP vinds to actin
The conformation of actin changes
This changes the affinity in the filament
What is the rate of ATP/ADP addition at the plus and minus ends of the microfilament
Rate of ADP addition is slower than ATP addition at both ends of the microfilament
ADP not readily added to the plus end
The rate if loss of ADP actin is greater than the rate of addition of ATP at the minus end, but at the plus end loss of ADP actin is faster than at the minus end
Where does ADP actin tend to end up in a microfilament
Tends to end up in older parts of the filament
Using a diagram, explain the concept of critical concentration
Treadmilling occurs when the concentration of free subunits is between the critical concentrations for the two ends
Plus End Critical Concentration :The concentration of monomers required for polymerization at the plus end.
Minus End Critical Concentration : The concentration of monomers required for polymerization at the minus end
Is above Cc+, the filament will grow at the plus end.
Is below Cc- , the filament will shrink at the minus end.
Is between Cc+ and Cc- , treadmilling can occur, where the filament grows at the plus end and shrinks at the minus end.
Critical Concentration: Describes the equilibrium concentration of free monomers required for no net growth or shrinkage at a filament end.
What are nucleators and why are they needed
Nucleators are proteins or complexes that facilitate the formation of new actin filaments or microtubules, a process known as nucleation
They are needed because spontaneous nucleation takes too long (as it relies on diffusion)
What are the two main types of nucleators and what are their main roles
What is the role of ARP 2/3
ARP= actin related proteins
They can act as a starting point for nucleation as they have a similar structure to Actin
How does ARP 2/3 help produce microfilaments
It holds the minus ends and allows the plus ends to grow
Why is growth of the branches (daughter filaments) important for a cell
They produce a force that pushes the plasma membrane forward at the leading edge of motile cells
(Cells need it to move)
What is the role of formins
They provide a template for the growing plus ends of microfilaments
2 actin subunits are held by formin
How does formin work to help nucleation/ filament formation
What are actin binding proteins and what do they do
What are the proteins involved in controlling the growth of microfilaments
What are filament severing proteins and what do they do
What is the role of filamin
What do filament binding proteins do. Name two types and what they do
What is the role of microtubules
What is the structure of microtubules
How does microtuble nucleation occur
What is the microtubule organising centre
How are microtubules organise themselves from the centrosome
What do centrosomes contain
-they contain a centriole pair
What are microtubules able to do if they are severed from their centriole
How does microtubule treadmilling work
What is dynamic instability and how does it occur
involves the rapid switching between phases of microtubule growth (polymerization) and shrinkage (depolymerization).
Beta tubulin binds GTP before polymerizing onto the growing end of a microtubule.
The β-tubulin subunit of the dimer hydrolyzes GTP to GDP after incorporation into the microtubule lattice.
Tubulin bound to GTP (GTP-tubulin) is more stable and promotes microtubule growth, while tubulin bound to GDP
(GDP-tubulin) is less stable and promotes depolymerization
A growing microtubule typically has a “GTP cap” at its plus end (the rapidly growing end), where GTP-tubulin dimers are added faster than GTP is hydrolyzed to GDP.
The presence of this GTP cap stabilizes the microtubule and promotes further growth.
If the rate of GTP hydrolysis exceeds the rate of GTP-tubulin addition, the GTP cap is lost, exposing GDP-tubulin. This destabilizes the microtubule and leads to rapid depolymerization or shrinkage.
Rescue: The switch from shrinkage to growth can occur if enough GTP-tubulin dimers are incorporated to re-establish the GTP cap, stabilizing the microtubule and allowing it to start growing again.
Draw a diagram to represent how dynamic instability and catastrophe occurs
Draw a graph to show how length of the microtubule varies over time
Why may dynamic instability be useful for a cell
What are 2 types of microtubule binding proteins and what do they do
What does MAP2 and tau do
How is tau targeted in Alzheimer’s
What are microtubule stabilising proteins and give an example
What do katanins do
Makes disassociation of microtubules more likely
How does katanin work
What drugs can be used to perturb the cytoskeleton
How can cell wall formation be guided by microtubules - draw a diagram to help explain this
What is the role of microtubules in cell division
Why is diffusion not enough for transport around the cell
What are the 3 main classes of motor proteins
How are energy and force produced for motor proteins
What kind of motor protein does prokaryotes have
They have a bacterial flagella
What are the 2 ways in which motor proteins are anchored
If elastic force exceeds resistance the track or motor will move (depending on which is anchored)
So if motor is anchored the track will move and vice Vera’s
What structures are conserved in motor proteins
Which class of motor protein is this
Kinesin
What class of motor protein is this
Cytoplasmic dynein
What class of motor protein is this
Myosin V
How do kinesins and dyneins work
Describe the structure of kinesins
Describe the structure of dynein
How do dyneins move across microtubules
As dynein-1 moves along an MT, ATP hydrolysis in the AAA+ ring of each monomer generates a series of conformational changes, which detach the monomer from the MT and reorient its linker domain to produce a net step toward the minus end
What is the function of dyneins
What is this a cross section of
How do ciliary dyneins cause the cilia to bend
How does dynein and Kinesin work together
Draw a diagram to show how kinesins and dyneins work in a cell
How does influenza hijack the cytoskeleton
What are the characteristics of the myosin superfamily
What is the structure of myosin
How do myosin motors produce force and move along the actin filament
What is the structure of actin and myosin in muscles
What happens when myosin goes wrong
What is the role of myosin motors in cell division
