unit 3 week 1 pt 1 Flashcards
What is the cytoskeleton, and what are its main components?
The cytoskeleton is a dynamic network of protein filaments that provides structural support and facilitates movement within eukaryotic cells. It consists of three major components: Microtubules (MTs), Actin filaments, and Intermediate filaments (IFs).
How does the cytoskeleton contribute to cell shape and structure?
It acts as a dynamic scaffold that provides structural support, determines cell shape, and resists deforming forces.
What role does the cytoskeleton play in organelle positioning?
It provides an internal framework that positions organelles within the cell, particularly in polarized epithelial cells.
How does the cytoskeleton facilitate intracellular transport?
It acts as a network of tracks that directs the movement of materials and organelles, such as transporting mRNA and moving vesicles.
How does the cytoskeleton enable cell movement?
It serves as a force-generating apparatus that moves cells in various ways, including crawling and using cilia and flagella.
What role does the cytoskeleton play in cell division?
It is responsible for separating chromosomes during mitosis and meiosis and splitting the parent cell during cytokinesis.
What are microtubules, and where are they found?
Microtubules are hollow, tubular structures composed of the protein tubulin, found in the cytoskeleton, mitotic spindle, centrioles, and cilia.
What are the primary functions of microtubules?
Microtubules provide structural support to the cell and facilitate intracellular transport.
What is the general shape and size of a microtubule?
Microtubules are hollow, rigid, tubular structures with an outer diameter of 25 nm and a wall thickness of ~4 nm.
What are microtubules composed of?
Microtubules are made of globular proteins arranged in longitudinal rows called protofilaments.
How many protofilaments make up the wall of a microtubule?
13 protofilaments are arranged side by side in a circular pattern within the wall.
What role do noncovalent interactions play in microtubule structure?
Noncovalent interactions between adjacent protofilaments help maintain microtubule structure and stability.
What are the building blocks of protofilaments?
Each protofilament is assembled from dimeric building blocks, consisting of one α-tubulin subunit and one β-tubulin subunit.
Why are protofilaments asymmetric?
Protofilaments are asymmetric because each tubulin dimer contains two nonidentical components.
What is the significance of microtubule polarity?
Microtubules have a plus (+) end terminated by β-tubulin and a minus (-) end terminated by α-tubulin, which is crucial for growth and directional movement.
What are microtubule-associated proteins (MAPs)?
MAPs are additional proteins that stabilize microtubules and promote their assembly by linking tubulin subunits together.
What is the primary function of MAPs?
MAPs help stabilize microtubules and promote their assembly.
How is the activity of some MAPs regulated?
The binding of MAPs to microtubules is controlled by phosphorylation and dephosphorylation of specific amino acid residues.
What is tau, and how is it linked to neurodegenerative diseases?
Tau is a MAP that stabilizes microtubules, and excessive phosphorylation of tau is associated with neurodegenerative diseases such as Alzheimer’s disease.
What are neurofibrillary tangles?
In Alzheimer’s patients, abnormally phosphorylated tau forms tangled filaments, contributing to neuronal death.
What is FTDP-17, and how is tau involved?
FTDP-17 is a neurodegenerative disease caused by tau mutations, indicating tau’s toxic role in neurons.
How do microtubules provide mechanical support to the cell?
Microtubules are stiff and can resist compressive forces, helping maintain cell shape.
How do microtubules influence cell shape in different cell types?
Microtubules form a radial array in cultured animal cells, align parallel in columnar epithelial cells, and extend through axons in nerve cells.
What role do microtubules play in plant cell shape?
In plant cells, microtubules influence cell wall formation and growth patterns.
How does cellulose synthesis relate to microtubules in plant cells?
Cellulose synthase is linked to cortical microtubules, guiding the alignment of cellulose microfibrils.
How do microtubules help maintain internal cell organization?
Microtubules position organelles like the ER and Golgi complex within the cell.
What happens when microtubules are disrupted?
Microtubule-disrupting drugs disperse the Golgi complex into scattered stacks.
What occurs when microtubules reassemble after drug removal?
The Golgi membranes return to their normal position near the nucleus.
How do microtubules contribute to intracellular movement?
Microtubules act as tracks for moving macromolecules and organelles.
How does microtubule disruption affect transport?
Disruption stops the transport of materials between membrane compartments.
Why is intracellular transport especially important in nerve cells?
Nerve cells rely on a highly organized cytoskeleton to transport materials across long axons.
What is the function of the neuron’s cell body in transport?
The cell body serves as the manufacturing center for proteins and vesicles.
How does axonal transport work?
Labeled proteins move along microtubules toward the axon terminal.
How fast does axonal transport occur?
The fastest transport moves at 5 µm per second.
What are the two directions of axonal transport?
Anterograde transport moves toward the axon terminal, while retrograde transport moves toward the cell body.
How are transport defects linked to neurological diseases?
Impaired transport is associated with neurological diseases like ALS.
What cytoskeletal structures are found in axons?
Axons contain actin filaments, intermediate filaments, and microtubules.
How is vesicle movement along microtubules studied?
Using video microscopy to track vesicles in real time.
What is the role of motor proteins in intracellular transport?
Motor proteins move cargo along microtubule tracks.
What are microtubule-organizing centers (MTOCs)?
Specialized cellular structures that regulate the location and orientation of microtubule assembly.
How does microtubule assembly occur?
It happens in two phases: nucleation and elongation.
How is nucleation different in vitro vs. in cells?
In vitro, nucleation is slow, while in cells, it happens rapidly due to MTOCs.
What is the primary MTOC in animal cells?
The centrosome.
What are the key components of a centrosome?
Two centrioles and pericentriolar material (PCM).
What is the structure of a centriole?
A cylinder made of nine triplets of microtubules arranged in a radial pattern.
How do new centrioles form?
A new daughter centriole forms at a right angle to an existing mother centriole.
How do centrosomes regulate microtubule polarity?
The minus ends of microtubules are anchored at the centrosome.
What happens when microtubules are disrupted?
Drugs like nocodazole depolymerize microtubules, but they rapidly reassemble after drug removal.
Where do newly formed microtubules originate?
They grow from the surrounding PCM.
How does microtubule organization vary by cell type?
Nonpolarized cells have microtubules radiating from a central centrosome, while polarized epithelial cells anchor at the apical end.
Can cells function without centrosomes?
Yes, some cells can form complex microtubular structures without centrosomes.
What disorders are linked to centrosome defects?
Microcephaly is linked to impaired neuronal proliferation and migration.
What are MTOCs other than centrosomes?
Basal bodies are another type of MTOC found at the base of cilia and flagella.
How are basal bodies related to centrioles?
They have an identical structure and can convert into each other.
Do plant cells have centrosomes or centrioles?
No, plant cells lack obvious MTOCs.
What are the key functions of MTOCs?
They control the number, polarity, and assembly of microtubules.
What is the common protein found in all MTOCs?
α-Tubulin, which is essential for microtubule nucleation.
How was α-tubulin discovered?
It was identified in the fungus Aspergillus through genetic screens.
How does α-tubulin contribute to microtubule formation?
α-Tubulin is concentrated in α-Tubulin Ring Complexes (α-TuRCs), which serve as templates for new microtubules.
How was α-TuRC identified?
Researchers used gold-labeled antibodies that bound to α-tubulin.
Are all microtubules equally stable?
No, their stability varies from highly labile to highly stable.
What proteins regulate microtubule stability?
MAPs stabilize microtubules, while +TIPs bind to the plus end and Katanin severs microtubules.
Are microtubules stable?
No, their stability varies:
* Highly labile (unstable): Mitotic spindle and cytoskeletal microtubules.
* Moderately stable: Mature neurons.
* Highly stable: Centrioles, cilia, and flagella.
What proteins regulate microtubule stability?
- MAPs (Microtubule-Associated Proteins): Stabilize microtubules.
- +TIPs: Bind to the plus end of growing microtubules.
- Katanin: Severs microtubules into smaller pieces.
How is microtubule stability modified?
Posttranslational modifications like glutamate attachment to tubulin regulate stability.
What conditions cause microtubule disassembly?
- Cold temperature
- Hydrostatic pressure
- High calcium levels
- Drugs (e.g., colchicine, vinblastine, vincristine, nocodazole)
How does the drug taxol affect microtubules?
It prevents disassembly, stopping new microtubule formation, which is why it’s used in cancer chemotherapy to kill rapidly dividing tumor cells.
How do plant microtubules change over the cell cycle?
They transition through four distinct arrays from one mitotic division to the next.
What is the cytoskeleton, and what are its main components?
The cytoskeleton is a dynamic network of protein filaments that provides structural support and facilitates movement within eukaryotic cells. It consists of three major components: Microtubules (MTs), Actin filaments, and Intermediate filaments (IFs).
How does the cytoskeleton contribute to cell shape and structure?
It acts as a dynamic scaffold that provides structural support, determines cell shape, and resists deforming forces.
What role does the cytoskeleton play in organelle positioning?
It provides an internal framework that positions organelles within the cell, particularly in polarized epithelial cells.
How does the cytoskeleton facilitate intracellular transport?
It acts as a network of tracks that directs the movement of materials and organelles, such as transporting mRNA and moving vesicles.
How does the cytoskeleton enable cell movement?
It serves as a force-generating apparatus that moves cells in various ways, including crawling and using cilia and flagella.
What role does the cytoskeleton play in cell division?
It is responsible for separating chromosomes during mitosis and meiosis and splitting the parent cell during cytokinesis.
What are microtubules, and where are they found?
Microtubules are hollow, tubular structures composed of the protein tubulin, found in the cytoskeleton, mitotic spindle, centrioles, and cilia.
What are the primary functions of microtubules?
Microtubules provide structural support to the cell and facilitate intracellular transport.
What is the general shape and size of a microtubule?
Microtubules are hollow, rigid, tubular structures with an outer diameter of 25 nm and a wall thickness of ~4 nm.
What are microtubules composed of?
Microtubules are made of globular proteins arranged in longitudinal rows called protofilaments.
How many protofilaments make up the wall of a microtubule?
13 protofilaments are arranged side by side in a circular pattern within the wall.
What role do noncovalent interactions play in microtubule structure?
Noncovalent interactions between adjacent protofilaments help maintain microtubule structure and stability.
What are the building blocks of protofilaments?
Each protofilament is assembled from dimeric building blocks, consisting of one α-tubulin subunit and one β-tubulin subunit.
Why are protofilaments asymmetric?
Protofilaments are asymmetric because each tubulin dimer contains two nonidentical components.
What is the significance of microtubule polarity?
Microtubules have a plus (+) end terminated by β-tubulin and a minus (-) end terminated by α-tubulin, which is crucial for growth and directional movement.
What are microtubule-associated proteins (MAPs)?
MAPs are additional proteins that stabilize microtubules and promote their assembly by linking tubulin subunits together.
What is the primary function of MAPs?
MAPs help stabilize microtubules and promote their assembly.
How is the activity of some MAPs regulated?
The binding of MAPs to microtubules is controlled by phosphorylation and dephosphorylation of specific amino acid residues.
What is tau, and how is it linked to neurodegenerative diseases?
Tau is a MAP that stabilizes microtubules, and excessive phosphorylation of tau is associated with neurodegenerative diseases such as Alzheimer’s disease.
What are neurofibrillary tangles?
In Alzheimer’s patients, abnormally phosphorylated tau forms tangled filaments, contributing to neuronal death.
What is FTDP-17, and how is tau involved?
FTDP-17 is a neurodegenerative disease caused by tau mutations, indicating tau’s toxic role in neurons.
How do microtubules provide mechanical support to the cell?
Microtubules are stiff and can resist compressive forces, helping maintain cell shape.
How do microtubules influence cell shape in different cell types?
Microtubules form a radial array in cultured animal cells, align parallel in columnar epithelial cells, and extend through axons in nerve cells.
What role do microtubules play in plant cell shape?
In plant cells, microtubules influence cell wall formation and growth patterns.
How does cellulose synthesis relate to microtubules in plant cells?
Cellulose synthase is linked to cortical microtubules, guiding the alignment of cellulose microfibrils.
How do microtubules help maintain internal cell organization?
Microtubules position organelles like the ER and Golgi complex within the cell.
What happens when microtubules are disrupted?
Microtubule-disrupting drugs disperse the Golgi complex into scattered stacks.
What occurs when microtubules reassemble after drug removal?
The Golgi membranes return to their normal position near the nucleus.
How do microtubules contribute to intracellular movement?
Microtubules act as tracks for moving macromolecules and organelles.
How does microtubule disruption affect transport?
Disruption stops the transport of materials between membrane compartments.
Why is intracellular transport especially important in nerve cells?
Nerve cells rely on a highly organized cytoskeleton to transport materials across long axons.
What is the function of the neuron’s cell body in transport?
The cell body serves as the manufacturing center for proteins and vesicles.
How does axonal transport work?
Labeled proteins move along microtubules toward the axon terminal.
How fast does axonal transport occur?
The fastest transport moves at 5 µm per second.
What are the two directions of axonal transport?
Anterograde transport moves toward the axon terminal, while retrograde transport moves toward the cell body.
How are transport defects linked to neurological diseases?
Impaired transport is associated with neurological diseases like ALS.
What cytoskeletal structures are found in axons?
Axons contain actin filaments, intermediate filaments, and microtubules.
How is vesicle movement along microtubules studied?
Using video microscopy to track vesicles in real time.
What is the role of motor proteins in intracellular transport?
Motor proteins move cargo along microtubule tracks.
What are microtubule-organizing centers (MTOCs)?
Specialized cellular structures that regulate the location and orientation of microtubule assembly.
How does microtubule assembly occur?
It happens in two phases: nucleation and elongation.
How is nucleation different in vitro vs. in cells?
In vitro, nucleation is slow, while in cells, it happens rapidly due to MTOCs.
What is the primary MTOC in animal cells?
The centrosome.
What are the key components of a centrosome?
Two centrioles and pericentriolar material (PCM).
What is the structure of a centriole?
A cylinder made of nine triplets of microtubules arranged in a radial pattern.
How do new centrioles form?
A new daughter centriole forms at a right angle to an existing mother centriole.
How do centrosomes regulate microtubule polarity?
The minus ends of microtubules are anchored at the centrosome.
What happens when microtubules are disrupted?
Drugs like nocodazole depolymerize microtubules, but they rapidly reassemble after drug removal.
Where do newly formed microtubules originate?
They grow from the surrounding PCM.
How does microtubule organization vary by cell type?
Nonpolarized cells have microtubules radiating from a central centrosome, while polarized epithelial cells anchor at the apical end.
Can cells function without centrosomes?
Yes, some cells can form complex microtubular structures without centrosomes.
What disorders are linked to centrosome defects?
Microcephaly is linked to impaired neuronal proliferation and migration.
What are MTOCs other than centrosomes?
Basal bodies are another type of MTOC found at the base of cilia and flagella.
How are basal bodies related to centrioles?
They have an identical structure and can convert into each other.
Do plant cells have centrosomes or centrioles?
No, plant cells lack obvious MTOCs.
What are the key functions of MTOCs?
They control the number, polarity, and assembly of microtubules.
What is the common protein found in all MTOCs?
α-Tubulin, which is essential for microtubule nucleation.
How was α-tubulin discovered?
It was identified in the fungus Aspergillus through genetic screens.
How does α-tubulin contribute to microtubule formation?
α-Tubulin is concentrated in α-Tubulin Ring Complexes (α-TuRCs), which serve as templates for new microtubules.
How was α-TuRC identified?
Researchers used gold-labeled antibodies that bound to α-tubulin.
Are all microtubules equally stable?
No, their stability varies from highly labile to highly stable.
What proteins regulate microtubule stability?
MAPs stabilize microtubules, while +TIPs bind to the plus end and Katanin severs microtubules.
Are microtubules stable?
No, their stability varies:
* Highly labile (unstable): Mitotic spindle and cytoskeletal microtubules.
* Moderately stable: Mature neurons.
* Highly stable: Centrioles, cilia, and flagella.
What proteins regulate microtubule stability?
- MAPs (Microtubule-Associated Proteins): Stabilize microtubules.
- +TIPs: Bind to the plus end of growing microtubules.
- Katanin: Severs microtubules into smaller pieces.
How is microtubule stability modified?
Posttranslational modifications like glutamate attachment to tubulin regulate stability.
What conditions cause microtubule disassembly?
- Cold temperature
- Hydrostatic pressure
- High calcium levels
- Drugs (e.g., colchicine, vinblastine, vincristine, nocodazole)
How does the drug taxol affect microtubules?
It prevents disassembly, stopping new microtubule formation, which is why it’s used in cancer chemotherapy to kill rapidly dividing tumor cells.
How do plant microtubules change over the cell cycle?
They transition through four distinct arrays from one mitotic division to the next.
