What happens to intermediate filaments as force increases?
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They become less flexible and start resisting the force.
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What happens to intermediate filaments as force increases?
They become less flexible and start resisting the force.
Why are intermediate filaments considered more mechanically robust?
Because they respond differently to forces compared to microtubules or actin filaments.
What are intermediate filaments?
A family of proteins with tissue-specific expression.
What ability do metastatic cells use to spread from localized cancer?
Their crawling ability.
What is the primary function of intermediate filaments?
To provide tensile strength.
What are the two types of motor proteins that move along microtubules?
Kinesins and dyneins.
What happens after nucleation in actin polymerization?
Monomers are added to either end of the filament.
What is the natural source of Taxol?
The Pacific yew tree (Taxus brevifolia).
What is a key characteristic of intermediate filaments?
Easily deformed and don’t rupture, maintaining cell integrity.
What are the three main components of the cytoskeleton?
Microtubules, actin filaments, and intermediate filaments.
What role does the ARP2/3 complex play in actin filament formation?
It nucleates filament formation to overcome the lag phase.
What is the primary function of neutrophils?
To chase bacteria through tissues or across a substratum.
What is the first step of actin polymerization?
Nucleation, where dimers and trimers are formed.
What interactions does the actin cytoskeleton stabilize?
Interactions between cells and between cells and the ECM.
What is the growth direction of actin filaments?
Actin filaments grow from their plus ends.
What are some examples of organizing centers for microtubules?
Centrosome, poles of a mitotic spindle, and basal body of a cilium.
How do intermediate filaments respond to low forces?
They will stretch.
What is the primary role of stabilizing proteins in actin filaments?
To prevent depolymerization and maintain filament integrity.
Name a common stabilizing protein for actin filaments.
Tropomyosin.
What is the role of cofilin in actin dynamics?
Cofilin severs actin filaments, promoting turnover and remodeling.
What type of actin associates with the rapidly growing barbed end?
Actin bound to ATP.
What is muscle myosin similar to?
Myosin that transports organelles.
What is one of the main functions of microtubules?
Maintenance of cell shape.
What role do capping proteins play in actin filament stabilization?
They bind to the ends of filaments to prevent further polymerization or depolymerization.
What is the function of WASp in actin polymerization?
WASp links external signals to the regulation of actin polymerization.
What is the lag phase in actin polymerization?
It is a delay in the polymerization of new actin filaments from existing ones.
What happens to actin filaments after cofilin severs them?
Severed filaments can lead to increased nucleation and polymerization of new actin filaments.
What happens in the presence of a high concentration of capping protein?
Cells form many short actin filaments.
How do microtubules contribute to cell division?
They form the mitotic spindle, which separates chromosomes during mitosis.
What is the role of ARP2/3 in neutrophils?
It triggers the growth of a branched network of actin filaments.
What role do actin filaments play in cell morphology?
They support and modify cell morphology.
How do kinesins and dyneins move along microtubules?
Using their globular heads.
What do microtubules usually grow out from?
An organizing center.
What type of tubulin is found at the plus end of a microtubule during disassembly?
GDP-bound tubulin.
What can happen to actin filaments when necessary?
They can be broken down.
Where are keratins prominently found?
In skin and hair.
What are intermediate filaments?
Intermediate filaments are a type of cytoskeletal component that provide structural support to cells.
How do monomers behave at the plus end of actin filaments?
Monomers are readily incorporated into the plus end.
What proteins are involved in generating short, branched filaments?
ARP2/3 and capping protein.
What does the ARP2/3 complex resemble?
Actin dimers.
What type of receptors do neutrophils contain?
Receptors that bind to bacterial peptides with formyl groups.
What happens when WASp is activated?
It associates with ARP2/3 and activates it, triggering actin polymerization.
What happens to the lag phase in the presence of preformed filaments?
There is no delay in actin polymerization.
What role does γ-tubulin play in microtubule assembly?
It helps in initiating microtubule assembly in the centrosome.
How does the cell recycle old actin filaments?
By severing them and allowing them to depolymerize.
What unique structures do neurons have to relay signals?
Long processes called axons and dendrites.
What does an immunofluorescence micrograph show?
The microtubule organization in liver epithelial cells.
How do antimitotic drugs affect microtubules?
They disrupt microtubule dynamics, which is crucial for cell division.
What is cell motility?
The ability of cells to move and navigate through their environment.
What do bipolar myosin filaments generate?
Force of contraction.
What role do myosins play in cells?
They generate changes in cell shape and transport vesicles and organelles.
How do actin filaments contribute to cell motility?
They polymerize and form structures that push the cell membrane forward.
How do intermediate filaments assemble?
Through coiled coil interactions.
Where are neurofilaments located?
In axons.
What is the structure formed by two monomers in intermediate filament assembly?
Parallel dimer.
What is the significance of external signals in cell motility?
They guide the direction and speed of cell movement.
What is a key characteristic of bipolar myosin filaments?
Motors on one side move in the opposite direction to motors on the other end.
At what angle do new filaments grow relative to existing filaments?
Approximately 70 degrees.
In which types of cells are intermediate filaments commonly found?
In epithelial cells, connective tissue cells, and neurons.
What is ARP2/3?
A protein complex that is activated by WASp to promote actin polymerization.
What occurs when calcium concentration increases?
Myosins become active and start pulling on the filaments, causing contraction.
What do dense, parallel arrays of actin filaments provide?
Increased mechanical strength.
What role does calcium play in muscle contraction?
Calcium triggers the contraction of actin and myosin filaments.
What happens to microtubule organization after taxol treatment?
Thick circumferential bundles of microtubules form around the periphery of the cell.
How do actin filaments compare to microtubules in terms of rigidity?
Actin filaments are more rigid but also rupture easily.
How do stabilizing proteins affect actin filament dynamics?
They enhance stability and can regulate filament growth.
How does cofilin affect filament stability?
Cofilin destabilizes actin filaments, leading to their disassembly.
What is the role of the centrosome in relation to microtubules?
It serves as an organizing center from which microtubules extend.
What is the significance of filament severing by cofilin?
It facilitates rapid changes in cell shape and motility.
What role do myosin filaments play in cell motility?
They interact with actin filaments to generate contractile forces.
In what conditions is cofilin activated?
Cofilin is activated in response to signaling pathways that promote actin turnover.
What is the basal body associated with?
A cilium.
What triggers the contraction of actin and myosin filaments?
Calcium.
What do cells use to regulate actin polymerization?
Actin nucleating factors.
How do microtubules facilitate organelle movement?
By providing tracks for organelle transport.
What type of mutations can lead to epidermolysis bullosa simplex?
Mutations in keratin genes.
What happens when receptors on neutrophils bind to bacterial peptides?
They activate ARP2/3, leading to actin polymerization.
What is the effect of low calcium levels on myosin activity?
Myosin is inactive.
Which proteins are used to generate structures like microvilli?
Villin and fimbrin.
How do dendrites and axons compare in length to the cell body?
They can be hundreds of times the length of the cell body.
How do neutrophils locate bacteria?
By tracking and chasing them.
How does the actin cytoskeleton contribute to the plasma membrane?
It provides structural and mechanical support.
What is the structural scaffold that holds all of the cellular organelles in place?
Cytoskeleton.
What is the function of intermediate filaments in cells?
They provide robust mechanical resistance.
How are actin filaments similar to microtubules?
Both are polarized.
What systems do metastatic cancer cells enter to spread to other organs?
The lymphatic or circulatory system.
What is the function of actin filaments in cells?
They provide stability for static structures and allow cells to change shape.
During which phase of the cell cycle does cytokinesis occur?
After mitosis or meiosis.
What is the most important nucleating factor for cell motility?
The ARP2/3 complex.
What is the leading edge in cell motility?
The part of the cell that extends forward in a certain direction.
What determines the direction of movement in microtubules?
The polarity of microtubules (plus and minus ends).
What protein subunits make up microtubules?
Tubulin proteins.
What protein are microtubules made of?
Tubulin.
How does a cell move its backend forward?
By pulling on attachments at the back end to detach them from the substratum.
What happens when defective keratins are expressed in the basal cell layer of the epidermis?
They produce epidermolysis bullosa simplex, causing skin blisters.
What effect does the continuous activation of ARP2/3 have on the cell?
It generates an expanding network of branched filaments that pushes forward the cell membrane.
What is the significance of the short gap between the actin-binding domains of villin and fimbrin?
It allows for the creation of tightly packed, parallel arrays of actin filaments.
What occurs over time to actin in the filament?
Actin hydrolyzes ATP to ADP.
What typically guides the direction of cell movement?
Some external chemical.
What are the mechanical properties of microtubules?
Easily deformed and rupture.
How do metastatic cancer cells move through tissues?
They crawl through tissues and along a substratum.
Which analogy best describes the cytoskeleton's function?
It acts like a 'wire' that supports and organizes the cell.
What are microtubules made of?
Hollow tubes made of globular tubulin subunits.
What is cytokinesis?
The process of cytoplasmic division that occurs at the end of cell division.
What structure do microtubules extend from during mitosis?
The two poles of a mitotic spindle.
What are protofilaments in microtubules?
Head-to-tail arrays of tubulin dimers arranged in parallel.
What activates the signaling pathway in neutrophils for actin polymerization?
Bacterial molecules.
What protein subunits make up microtubules?
Tubulin dimers, consisting of alpha and beta tubulin.
What role do actin filaments play in the cell?
They are involved in cell shape, motility, and division.
How do microtubules contribute to cell division?
They form the mitotic spindle, which separates chromosomes during cell division.
What is the result of actin polymerization triggered by WASp and ARP2/3?
Cell motility.
What role does capping protein play in filament dynamics?
It ensures that the filaments remain short.
What is required for cells to initiate motility related to actin?
Regulation of when and where to polymerize actin.
What happens to myosin activity when calcium levels fall?
Myosins lose activity, releasing the actin filaments and relaxing the cell.
What is the significance of the network formed by intermediate filaments?
It increases the mechanical strength of the cells and tissue, protecting against external stress.
What is the relationship between cell morphology and cell function?
Cell morphology facilitates cell function.
What do cells follow to move in a specific direction?
The concentration gradient of a single chemical.
What are antimitotic drugs used for?
Treatment of human cancer.
What role do actin and myosin filaments play in cells?
They allow cells to form different morphologies.
What ability does the actin cytoskeleton provide to cells?
It allows cells to change their morphology and to move.
What are the main components involved in cell motility?
Actin filaments, myosin filaments, and various signaling pathways.
What is the consequence of destabilization of actin filaments?
It can lead to loss of cell shape and motility.
Which end of actin filaments is the fast-growing end?
The plus end.
What is the significance of metastatic cancer cells' movement?
It allows them to escape localized cancer and spread to other organs.
How do microtubules contribute to cell motility?
Through structures like cilia or flagella.
What structure forms during cytokinesis in animal cells?
The cleavage furrow.
What role do microtubules play during cell division?
They assist in chromosome movements.
What role do attachments between the cell and the substratum play?
They provide something for the cell to push against and stabilize the leading edge.
What happens when one actin monomer associates with ARP2/3?
It forms a stable platform for filament growth.
How does cytokinesis differ in plant cells compared to animal cells?
Plant cells form a cell plate, while animal cells form a cleavage furrow.
What happens when myosin filaments pull on actin filaments attached to different regions of the cell membrane?
The cell contracts at these two regions.
What are intermediate filaments primarily responsible for?
Providing mechanical strength to the cell.
What is cell motility?
The ability of a cell to move and navigate through its environment.
Where do intermediate filaments extend from and to?
From the nucleus to the cell membrane.
What is Taxol (Paclitaxel) used for?
It is a drug that affects microtubule organization.
What is the average speed of neutrophils?
~ 0.1 to 0.2 μm/s.
What happens if GTP is hydrolyzed more rapidly than new subunits are added to a microtubule?
It leads to disassembly and shrinkage of the microtubule.
Is actin polymerization a reversible process?
Yes, actin polymerization is reversible.
Which class of intermediate filaments is the largest?
Keratin, with approximately 50 members.
What role do capping proteins play in actin filaments?
They control the length of actin filaments.
What are microtubules?
Cylindrical structures made of tubulin proteins that are part of the cytoskeleton.
What are the three steps involved in cell motility?
Pushing, attaching, and pulling.
How do actin filaments interact with myosin filaments?
Actin filaments can be used by myosin filaments to generate tension on the cell membrane and cause contraction.
What feature allows muscle myosin to polymerize into filaments?
A longer coiled coil domain.
What are microtubules composed of?
Tubulin protein subunits.
What structure is formed by two antiparallel dimers?
Antiparallel tetramer.
What do mutations in intermediate filaments cause?
Blistering diseases.
What do protofilaments consist of?
Antiparallel tetramers.
What role do microtubules play in intracellular transport?
They serve as tracks for motor proteins like kinesin and dynein to transport cellular cargo.
How can cells specify where actin polymerization occurs?
By controlling the activity and location of nucleating factors.
What supports microvilli in cells?
Parallel arrays of long actin filaments.
What is the primary function of intermediate filaments?
To integrate cells into a mechanical network.
What is the state of actin when it is incorporated into new filaments?
Actin is bound to ATP.
How does coordinated actin polymerization contribute to cell motility?
It pushes forward the cell membrane to drive cell motility.
What role do external signals play in actin polymerization?
They control the location of actin polymerization via activation of ARP2/3.
Why is cell motility dependent on forming short actin filaments?
Because long filaments are less rigid and wouldn’t support the cell membrane.
How does ADP-actin behave compared to ATP-actin?
ADP-actin dissociates more rapidly from filaments than ATP-actin.
What is the primary function of microtubules?
To provide structural support and shape to cells, and to facilitate intracellular transport.
What is the function of lamins?
They localize to the inner nuclear membrane.
How is WASp activated?
By receptors in the cell membrane that bind external signaling molecules.
What is the role of the contractile ring in cytokinesis?
It helps to pinch the cell into two daughter cells.
What are some examples of proteins that make up intermediate filaments?
Keratin, vimentin, and neurofilaments.
What role does cofilin play in actin filament dynamics?
Cofilin severs actin filaments leading to depolymerization.
What role do microtubules play in intracellular transport?
They serve as tracks for motor proteins to transport cellular materials.
What does cofilin bind to in actin filaments?
Cofilin binds to the sides of actin filaments and induces a twist.
What is the role of microvilli in enterocytes?
To increase the overall surface area for nutrient uptake.
What happens to ATP during actin filament polymerization?
ATP is hydrolyzed to ADP.
What does muscle myosin lack compared to myosin that transports organelles?
A domain for binding organelles.
What is the primary function of the cytoskeleton?
To provide structural support and shape to the cell.
How do capping proteins affect the growth of actin filaments?
They bind to plus ends and prevent further addition of monomers to stop growth.
What is the process called where ATP-actin is added at the barbed end while ADP-actin dissociates from the pointed end?
Treadmilling.
How do intermediate filaments differ from microtubules and actin filaments?
Intermediate filaments are more stable and less dynamic compared to microtubules and actin filaments.
What stabilizes the minus ends of actin filaments?
Nucleating factors.
What are the components of tubulin dimers?
α-tubulin and β-tubulin.
What generates the force for a cell to move across a surface?
The cell pushes forward a broad section of the plasma membrane.
What is the dynamic instability of microtubules?
The ability of microtubules to rapidly grow and shrink, allowing for cellular adaptability.
What structures do enterocytes form to increase nutrient absorption?
Microvilli.
How does cofilin differentiate between old and new actin filaments?
Cofilin only binds to filaments with actin that is bound to ADP.
What are microtubules?
Cylindrical structures made of tubulin proteins that are part of the cytoskeleton.
What is the primary function of microtubules?
To provide structural support and shape to cells, and to facilitate intracellular transport.
What is the primary function of intermediate filaments?
To provide mechanical strength and stability to cells.
What happens at the minus ends of actin filaments?
They add monomers very slowly and often shrink.
What are some examples of cell contraction?
Contraction of muscle cells, contraction during wound healing, and cytokinesis.
How does ARP2/3 contribute to filament formation?
By nucleating the polymerization of new filaments and binding to the side of existing filaments.
How does the bipolar arrangement of myosin filaments affect contraction?
It allows them to pull on two different actin filaments.
What is the function of myosin filaments?
They interact with actin filaments to facilitate muscle contraction.
What contributes to the tremendous strength of intermediate filaments?
Extensive lateral interactions.
What is the result of actin polymerization in neutrophils?
It pushes the cell membrane towards the source of the bacterial peptides.
What is the function of cofilin in the cell?
To sever old filaments and generate a constant supply of actin monomer for new filament growth.
How do intermediate filaments interact with neighboring cells?
They interact with proteins that bind to the cell membranes of neighboring cells.
How many proteins are in the ARP2/3 complex?
It is a set of proteins, two of which resemble actin.
Why does the cell need a continuous supply of actin monomers?
To polymerize new filaments for pushing forward the cell membrane.
What triggers the skin blisters in epidermolysis bullosa simplex?
Very slight mechanical stress that ruptures the basal cells.
Why do neurons need to provide structural support?
To maintain the structures of axons and dendrites.
In which type of cells are intermediate filaments predominantly found?
In cells that face significant mechanical stress, such as skin cells.
What happens when cofilin induces a twist in the actin filament?
The filament severs, exposing a minus end for depolymerization.
When can cofilin bind to and sever an actin filament?
When most of the filament is actin - ADP.
How does the cytoskeleton contribute to cell motility?
By facilitating movement through dynamic restructuring and interaction with motor proteins.
What role do actin filaments play in cell motility?
They enable cell movement by polymerizing and forming structures like lamellipodia and filopodia.
How many different types of cells are in the human body?
Over 200 different types.
What is the primary function of enterocytes?
To absorb nutrients from the lumen of the intestine and release them to the bloodstream.
What is the primary function of the cytoskeleton?
To provide structural support and shape to the cell.
What are the main components of the cytoskeleton?
Microtubules, actin filaments, and intermediate filaments.
What is the significance of motor proteins in cell motility?
They transport cellular cargo along the cytoskeleton and facilitate muscle contraction.
