What is the primary function of the cytoskeleton?
To provide structural support and shape to the cell.
p.1
Cell Motility Mechanisms
How does the cytoskeleton contribute to cell motility?
By facilitating movement through dynamic reorganization of its components.
What are the main components of the cytoskeleton?
Microtubules, actin filaments, and intermediate filaments.
p.1
Actin Filaments and Cell Morphology
What role do actin filaments play in cell motility?
They enable cell movement by polymerizing and forming structures like lamellipodia and filopodia.
p.41
Cell Motility Mechanisms
What do cells follow to move in a specific direction?
The concentration gradient of a single chemical.
p.25
Role of Calcium in Muscle Contraction
What role does calcium play in muscle contraction?
Calcium triggers the contraction of actin and myosin filaments.
p.5
Microtubules Structure and Function
What are protofilaments in microtubules?
Head-to-tail arrays of tubulin dimers arranged in parallel.
p.31
Intermediate Filaments and Mechanical Strength
How do actin filaments compare to microtubules in terms of rigidity?
Actin filaments are more rigid but also rupture easily.
p.51
Intermediate Filaments and Mechanical Strength
What do intermediate filaments provide to cells?
Robust mechanical resistance.
p.51
Actin Filaments and Cell Morphology
What role do actin and myosin filaments play in cells?
They allow cells to form different morphologies.
p.29
Intermediate Filaments and Mechanical Strength
What is the primary function of intermediate filaments?
To integrate cells into a mechanical network.
p.22
Myosin Filaments and Cell Contraction
What role do myosins play in cells?
They generate changes in cell shape and transport vesicles and organelles.
Which analogy best describes the cytoskeleton's function?
It acts like a wire, providing structure and support.
p.38
Cell Motility Mechanisms
What is cell motility?
The ability of cells to move and navigate through their environment.
p.8
Microtubules Structure and Function
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.
p.40
Cell Motility Mechanisms
What ability do metastatic cells use to spread to other organs?
Their crawling ability to escape from localized cancer.
p.17
Actin Polymerization and Regulation
What happens to ATP during actin filament polymerization?
ATP is hydrolyzed to ADP.
p.51
Cell Motility Mechanisms
How does coordinated actin polymerization contribute to cell movement?
It pushes forward the cell membrane to drive cell motility.
p.12
Microtubules Structure and Function
What does an immunofluorescence micrograph show in liver epithelial cells before taxol treatment?
The microtubule organization before the addition of taxol.
p.13
Microtubules Structure and Function
How do kinesins and dyneins move along microtubules?
Using their globular heads.
p.31
Intermediate Filaments and Mechanical Strength
What are the mechanical properties of microtubules?
Easily deformed and rupture.
p.11
Microtubules Structure and Function
How do antimitotic drugs affect microtubules?
They disrupt microtubule function, inhibiting cell division.
p.33
Intermediate Filaments and Mechanical Strength
Which class of intermediate filaments is the largest?
Keratin, with approximately 50 members.
p.49
External Signals in Actin Polymerization
What role do external signals play in actin polymerization?
They control the location of actin polymerization via activation of ARP2/3.
p.21
Intermediate Filaments and Mechanical Strength
What do dense, parallel arrays of actin filaments provide?
Increased mechanical strength.
p.40
Cell Motility Mechanisms
What systems do metastatic cells enter to spread cancer?
The lymphatic or circulatory system.
p.5
Microtubules Structure and Function
What determines the direction of movement in microtubules?
The polarity of microtubules (plus and minus ends).
p.12
Microtubules Structure and Function
What is Taxol (Paclitaxel) used for?
It is a drug that affects microtubule organization.
p.20
Cofilin and Actin Filament Recycling
How does cofilin affect the dynamics of actin filaments?
By severing filaments, cofilin increases the number of free barbed ends for polymerization.
p.23
Myosin Filaments and Cell Contraction
What is muscle myosin similar to?
Myosin that transports organelles.
p.36
Intermediate Filaments and Mechanical Strength
What triggers the blisters in epidermolysis bullosa simplex?
Very slight mechanical stress that ruptures the basal cells.
p.14
Microtubules Structure and Function
What is the dynamic nature of microtubules?
They can rapidly grow and shrink, allowing for flexibility in cellular processes.
p.49
External Signals in Actin Polymerization
How is WASp activated?
By receptors in the cell membrane that bind external signaling molecules.
p.32
Intermediate Filaments and Mechanical Strength
How do intermediate filaments assemble?
Through coiled coil interactions.
p.36
Intermediate Filaments and Mechanical Strength
What type of mutations lead to epidermolysis bullosa simplex?
Mutations in keratin genes.
p.17
Actin Polymerization and Regulation
How does ADP-actin behave compared to ATP-actin?
ADP-actin dissociates more rapidly from filaments than ATP-actin.
p.30
Intermediate Filaments and Mechanical Strength
What happens to intermediate filaments as the force increases?
They become less flexible and start resisting the force.
p.16
Actin Polymerization and Regulation
What is the first step of actin polymerization?
Nucleation, where dimers and trimers are formed.
p.32
Intermediate Filaments and Mechanical Strength
What are protofilaments?
Structures formed by the assembly of tetramers.
p.45
Actin Polymerization and Regulation
What is the direction of growth for actin filaments?
Actin filaments grow from their plus ends.
p.7
Microtubules Structure and Function
What are microtubules?
Cylindrical structures made of tubulin proteins that are part of the cytoskeleton.
p.20
Cofilin and Actin Filament Recycling
What type of actin filaments does cofilin preferentially bind to?
Cofilin preferentially binds to ADP-actin filaments.
p.40
Cell Motility Mechanisms
How do metastatic cancer cells move through tissues?
They crawl through tissues and along a substratum.
p.14
Microtubules Structure and Function
What is the main function of microtubules in cells?
To provide structural support and facilitate intracellular transport.
p.31
Intermediate Filaments and Mechanical Strength
What is a key characteristic of intermediate filaments?
Easily deformed and don’t rupture, maintaining cell integrity.
p.6
Microtubules Structure and Function
What are microtubules made of?
Hollow tubes made of globular tubulin subunits.
p.22
Actin Filaments and Cell Morphology
What is the function of actin filaments in cells?
They provide stability for static structures and allow cells to change shape.
p.50
Actin Polymerization and Regulation
What type of receptors do neutrophils contain?
Receptors that bind to bacterial peptides with formyl groups.
p.23
Myosin Filaments and Cell Contraction
What feature allows muscle myosin to polymerize into filaments?
A longer coiled coil domain.
p.36
Intermediate Filaments and Mechanical Strength
What happens when defective keratins are expressed in the basal cell layer of the epidermis?
They produce epidermolysis bullosa simplex, causing skin blisters.
p.21
Actin Polymerization and Regulation
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.
p.27
Cell Motility Mechanisms
What is cytokinesis?
The process of cytoplasmic division that occurs at the end of cell division.
p.20
Cofilin and Actin Filament Recycling
What is the significance of filament severing by cofilin?
It facilitates actin turnover and recycling, essential for cell motility and shape changes.
p.6
Microtubules Structure and Function
What is one of the main functions of microtubules?
Maintenance of cell shape.
p.29
Intermediate Filaments and Mechanical Strength
How do intermediate filaments interact with neighboring cells?
They interact with proteins that bind to proteins in the cell membranes of neighboring cells.
p.5
Microtubules Structure and Function
What role does γ-tubulin play in microtubule assembly?
It helps in initiating microtubule assembly in the centrosome.
p.12
Microtubules Structure and Function
What is the natural source of Taxol?
The Pacific yew tree (Taxus brevifolia).
p.4
Myosin Filaments and Cell Contraction
What is the function of myosin filaments?
They interact with actin filaments to facilitate muscle contraction.
p.19
Actin Polymerization and Regulation
Which proteins are involved in the stabilization of actin filaments?
Capping proteins, tropomyosin, and others.
p.14
Microtubules Structure and Function
What are microtubules primarily composed of?
Tubulin protein subunits.
p.30
Intermediate Filaments and Mechanical Strength
What is the primary function of intermediate filaments?
To provide tensile strength.
p.29
Intermediate Filaments and Mechanical Strength
Where do intermediate filaments extend from and to?
From the nucleus to the cell membrane.
p.24
Myosin Filaments and Cell Contraction
How does the bipolar arrangement of myosin filaments affect contraction?
It allows myosin to pull on two different actin filaments.
p.12
Microtubules Structure and Function
What changes occur in microtubule organization after taxol treatment?
Thick circumferential bundles of microtubules form around the periphery of the cell.
p.46
Actin Polymerization and Regulation
What role do capping proteins play in actin filaments?
They control the length of actin filaments.
p.38
Cell Motility Mechanisms
What are the main components involved in cell motility?
Cytoskeleton, motor proteins, and signaling pathways.
p.19
Actin Polymerization and Regulation
What is the primary role of actin filament stabilization?
To maintain the structural integrity and functionality of the cytoskeleton.
p.14
Cell Motility Mechanisms
What role do microtubules play in cell motility?
They are involved in the movement of cilia and flagella.
p.38
Cell Motility Mechanisms
How do actin filaments contribute to cell motility?
They provide structural support and enable cell shape changes necessary for movement.
p.22
Cell Motility Mechanisms
What are some examples of cell contraction?
Contraction of all muscle cells, contraction during wound healing, and cytokinesis.
p.50
Actin Polymerization and Regulation
What happens when receptors on neutrophils bind to bacterial peptides?
They activate ARP2/3, leading to actin polymerization.
p.24
Role of Calcium in Muscle Contraction
What happens when calcium levels fall?
Myosins lose activity, releasing the actin filaments and relaxing the cell.
p.11
Microtubules Structure and Function
What are antimitotic drugs used for?
Treatment of human cancer.
p.21
Actin Filaments and Cell Morphology
What supports microvilli in cells?
Parallel arrays of long actin filaments.
p.20
Cofilin and Actin Filament Recycling
What is the role of cofilin in actin filaments?
Cofilin severs actin filaments, promoting their disassembly.
p.33
Intermediate Filaments and Mechanical Strength
What are intermediate filaments?
A family of proteins with tissue-specific expression.
What is the primary function of the cytoskeleton?
To provide structural support and shape to the cell.
p.14
Microtubules Structure and Function
How do microtubules contribute to cell division?
They form the mitotic spindle, which separates chromosomes during mitosis.
p.34
Intermediate Filaments and Mechanical Strength
What are intermediate filaments?
Intermediate filaments are a type of cytoskeletal component that provide structural support to cells.
p.49
External Signals in Actin Polymerization
What is the function of WASp in actin polymerization?
WASp links external signals to the regulation of actin polymerization.
p.27
Cell Motility Mechanisms
When does cytokinesis occur?
After mitosis or meiosis.
What are the three main components of the cytoskeleton?
Microtubules, actin filaments, and intermediate filaments.
p.22
Myosin Filaments and Cell Contraction
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.
p.24
Role of Calcium in Muscle Contraction
What occurs when calcium concentration increases?
Myosins become active and start pulling on the filaments, causing cell contraction.
p.42
Cell Motility Mechanisms
What are the three steps involved in cell motility?
Pushing, attaching, and pulling.
p.4
Intermediate Filaments and Mechanical Strength
What are intermediate filaments primarily responsible for?
Providing mechanical strength to the cell.
p.49
External Signals in Actin Polymerization
What is the significance of ARP2/3 in cell motility?
It is activated by WASp to trigger the polymerization of actin filaments.
p.42
Cell Motility Mechanisms
What is the leading edge in cell motility?
The part of the cell that extends forward in a certain direction.
p.4
Microtubules Structure and Function
What are microtubules composed of?
Tubulin protein subunits.
p.44
Actin Polymerization and Regulation
What is the role of ARP2/3 in filament formation?
It nucleates filament formation to overcome the lag phase.
p.45
Actin Polymerization and Regulation
Are actin filaments polarized?
Yes, like microtubules, actin filaments are polarized.
p.27
Cell Motility Mechanisms
What is the result of cytokinesis?
Two daughter cells are formed, each with its own nucleus and cytoplasm.
p.34
Intermediate Filaments and Mechanical Strength
How do intermediate filaments differ from microtubules and actin filaments?
Intermediate filaments are more stable and less dynamic compared to microtubules and actin filaments.
p.6
Microtubules Structure and Function
What role do microtubules play during cell division?
They assist in chromosome movements.
p.46
Actin Polymerization and Regulation
How do capping proteins affect the growth of actin filaments?
They bind to plus ends and prevent further addition of monomers to stop growth.
p.38
Cell Motility Mechanisms
What role do motor proteins play in cell motility?
They transport cellular components and facilitate movement along the cytoskeleton.
p.15
Actin Filaments and Cell Morphology
What interactions does the actin cytoskeleton stabilize?
Interactions between cells and between cells and the ECM.
p.45
Actin Polymerization and Regulation
How do monomers incorporate into actin filaments?
Monomers are readily incorporated into the plus end.
p.48
Actin Polymerization and Regulation
How does ARP2/3 contribute to filament formation?
It nucleates the polymerization of new filaments by binding to the side of existing filaments.
p.15
Actin Filaments and Cell Morphology
What ability does the actin cytoskeleton provide to cells?
The ability to change their morphology and to move.
p.47
Cofilin and Actin Filament Recycling
Why does the cell need a continuous supply of actin monomers?
To support the continuous pushing forward of the cell membrane.
p.23
Myosin Filaments and Cell Contraction
What does muscle myosin lack compared to myosin that transports organelles?
A domain for binding organelles.
p.16
Actin Polymerization and Regulation
What happens after nucleation in actin polymerization?
Monomers are added to either end of the filament.
p.4
Actin Filaments and Cell Morphology
What role do actin filaments play in the cell?
They are involved in cell shape, motility, and division.
p.9
Microtubules Structure and Function
What are examples of organizing centers for microtubules?
Centrosome, poles of a mitotic spindle, and basal body of a cilium.
p.6
Microtubules Structure and Function
How do microtubules contribute to cell motility?
Through structures like cilia or flagella.
p.34
Intermediate Filaments and Mechanical Strength
What are some examples of proteins that make up intermediate filaments?
Keratin, vimentin, and neurofilaments.
p.19
Actin Polymerization and Regulation
What is the effect of tropomyosin on actin filaments?
It stabilizes the filaments and regulates interactions with other proteins.
p.47
Cofilin and Actin Filament Recycling
How does the cell recycle old actin filaments?
By severing them and allowing them to depolymerize.
p.39
Cell Motility Mechanisms
What is the primary function of neutrophils?
To chase bacteria through tissues or across a substratum.
p.2
Actin Filaments and Cell Morphology
What is the significance of cell morphology?
It facilitates cell function.
p.2
Actin Filaments and Cell Morphology
Why do enterocytes form microvilli?
To increase the overall surface area for nutrient uptake.
p.30
Intermediate Filaments and Mechanical Strength
Why are intermediate filaments considered more mechanically robust?
Because they resist higher forces better than microtubules or actin filaments.
p.15
Actin Filaments and Cell Morphology
What role do actin filaments play in cell morphology?
They support and modify cell morphology.
p.32
Intermediate Filaments and Mechanical Strength
What contributes to the tremendous strength of intermediate filaments?
Extensive lateral interactions.
p.29
Intermediate Filaments and Mechanical Strength
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.
p.15
Actin Filaments and Cell Morphology
How does the actin cytoskeleton contribute to the plasma membrane?
It provides structural and mechanical support.
p.33
Intermediate Filaments and Mechanical Strength
What is the function of lamins?
They localize to the inner nuclear membrane.
p.29
Intermediate Filaments and Mechanical Strength
In which types of cells are intermediate filaments predominantly found?
In cells that face significant mechanical stress, such as skin cells.
p.46
Actin Polymerization and Regulation
What happens in the presence of a high concentration of capping protein?
Cells form many short actin filaments.
p.50
Actin Polymerization and Regulation
What is the result of actin polymerization in neutrophils?
It pushes the cell membrane towards the source of the bacterial peptides.
p.49
Cell Motility Mechanisms
How do cells move in response to external signals?
They integrate the location of the external signal with proteins that regulate actin polymerization.
p.42
Cell Motility Mechanisms
How does a cell move its backend forward?
By pulling on attachments at the back end to detach them from the substratum.
p.48
Cofilin and Actin Filament Recycling
What is the function of cofilin in filament regulation?
It severs old filaments to generate a constant supply of actin monomer for new filament growth.
p.47
Cofilin and Actin Filament Recycling
What is the significance of the twist induced by cofilin?
It causes the filament to sever, exposing a minus end for depolymerization.
p.39
Cell Motility Mechanisms
How do neutrophils locate bacteria?
By tracking and chasing them.
p.34
Intermediate Filaments and Mechanical Strength
What is the primary function of intermediate filaments?
To provide mechanical strength and stability to cells.
p.46
Cell Motility Mechanisms
Why is cell motility dependent on forming short actin filaments?
Because long filaments are less rigid and wouldn’t support the cell membrane.
p.43
Actin Polymerization and Regulation
What is the lag phase in actin polymerization?
A delay in the polymerization of new actin filaments.
p.9
Microtubules Structure and Function
What is the role of the centrosome in relation to microtubules?
It serves as an organizing center from which microtubules extend.
p.49
External Signals in Actin Polymerization
What happens when WASp is activated?
It associates with ARP2/3 and activates it, triggering actin polymerization.
p.7
Microtubules Structure and Function
How do microtubules contribute to cell division?
They form the mitotic spindle, which separates chromosomes during mitosis.
p.34
Intermediate Filaments and Mechanical Strength
In which types of cells are intermediate filaments commonly found?
In epithelial cells, connective tissue cells, and neurons.
p.9
Microtubules Structure and Function
What is the function of the basal body in relation to microtubules?
It acts as an organizing center for microtubules in cilia.
p.48
Actin Polymerization and Regulation
At what angle do new filaments grow in relation to existing filaments?
Approximately 70 degrees.
p.19
Actin Polymerization and Regulation
Why is stabilization of actin filaments important for cells?
It is crucial for cell shape, motility, and division.
p.47
Cofilin and Actin Filament Recycling
What does cofilin bind to in actin filaments?
Cofilin binds to the sides of actin filaments and induces a twist.
p.7
Microtubules Structure and Function
What is the primary function of microtubules?
To provide structural support and shape to cells, and to facilitate intracellular transport.
p.20
Cofilin and Actin Filament Recycling
What happens to actin filaments after cofilin severs them?
The severed filaments can be rapidly disassembled or recycled for new filament formation.
p.44
Actin Polymerization and Regulation
What is the composition of the ARP2/3 complex?
A set of proteins, two of which resemble actin.
p.48
Actin Polymerization and Regulation
What proteins are involved in generating short, branched filaments?
ARP2/3 and capping protein.
p.44
Actin Polymerization and Regulation
How does an actin monomer interact with ARP2/3?
When one actin monomer associates with ARP2/3, it forms a stable platform for filament growth.
p.42
Cell Motility Mechanisms
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.
p.43
Actin Polymerization and Regulation
What is required for cells to initiate motility related to actin?
Regulating when and where they polymerize actin.
p.2
Actin Filaments and Cell Morphology
What is the primary function of enterocytes?
To absorb nutrients from the lumen of the intestine.
p.23
Myosin Filaments and Cell Contraction
What is a key characteristic of myosin filaments?
They are bipolar, with motors on one side moving in the opposite direction to those on the other side.
p.7
Microtubules Structure and Function
What protein subunits make up microtubules?
Tubulin dimers, consisting of alpha and beta tubulin.
p.19
Actin Polymerization and Regulation
How do capping proteins stabilize actin filaments?
By binding to the ends of the filaments to prevent further polymerization or depolymerization.
p.6
Microtubules Structure and Function
How do microtubules affect organelle movement?
They facilitate the movement of organelles within the cell.
p.38
Cell Motility Mechanisms
What is the significance of cell motility in biological processes?
It is crucial for processes like wound healing, immune response, and embryonic development.
p.48
Actin Polymerization and Regulation
What role does capping protein play in filament dynamics?
It ensures that the filaments remain short.
p.47
Cofilin and Actin Filament Recycling
What happens to actin over time in the filament?
Actin hydrolyzes ATP to ADP.
p.2
Actin Filaments and Cell Morphology
What do neurons need to maintain their long processes?
Structural support and biochemical components.
p.16
Actin Polymerization and Regulation
Is actin polymerization a reversible process?
Yes, the filaments can be broken down when necessary.
p.50
Actin Polymerization and Regulation
What is the role of ARP2/3 in neutrophils?
It triggers the growth of a branched network of actin filaments.
p.43
Actin Polymerization and Regulation
What do cells use to regulate actin polymerization?
Actin nucleating factors.
p.16
Actin Polymerization and Regulation
What structural levels are involved in actin filaments?
Primary, secondary, tertiary, and quaternary structures.
p.43
Actin Polymerization and Regulation
What happens to the lag phase in the presence of preformed filaments?
There is no delay in actin polymerization.
p.45
Actin Polymerization and Regulation
What happens at the minus ends of actin filaments?
Minus ends add monomers very slowly and often shrink.
p.9
Microtubules Structure and Function
What structure do microtubules extend from during cell division?
The two poles of a mitotic spindle.
p.1
Microtubules Structure and Function
What is the significance of microtubules in cell motility?
They provide tracks for the transport of organelles and vesicles within the cell.
p.43
Actin Polymerization and Regulation
How can cells specify where actin polymerization occurs?
By controlling the activity and location of nucleating factors.
p.48
Cell Motility Mechanisms
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.
p.4
Cell Motility Mechanisms
What is cell motility?
The ability of a cell to move and change position.
p.24
Myosin Filaments and Cell Contraction
What is the effect of myosin filaments on the cell membrane during contraction?
They cause the cell to contract at different regions of the cell membrane.
p.7
Microtubules Structure and Function
What is the dynamic instability of microtubules?
The ability of microtubules to rapidly grow and shrink, allowing for cellular adaptability.
p.47
Cofilin and Actin Filament Recycling
When can cofilin bind and sever the actin filament?
When most of the filament is actin - ADP.
p.47
Cofilin and Actin Filament Recycling
What role does cofilin play in actin filament dynamics?
Cofilin severs actin filaments leading to depolymerization.
p.42
Cell Motility Mechanisms
What generates the force for a cell to move across a surface?
The cell pushes forward a broad section of the plasma membrane.
p.2
Actin Filaments and Cell Morphology
How do axons and dendrites contribute to neuronal function?
They send and receive signals between cells.
p.47
Cofilin and Actin Filament Recycling
How does cofilin differentiate between old and new actin filaments?
Cofilin only binds to filaments with actin that is bound to ADP.
p.2
Actin Filaments and Cell Morphology
How many different types of cells are in the human body?
Over 200 different types.
