The Cytoskeleton Flashcards
What are the three types of cytoskeleton filaments?
- Intermediate filaments: mechanical strength.
- Microtubules: organelles and intracellular transport.
- Actin: cell shape and movement.
What are the functions of the cytoskeleton?
- Cell shape & polarity
- Cell motility
- Cell plasticity
- Segregation of chromosomes
- Endocytosis
- Secretion
- Segregation of organelles
- Communication between organelles
What are the roles of microtubules in interphase?
- Structural support & shape
- Cell motility
- Positioning of organelles
- Movement of organelles and molecules
What are the roles of microtubules in mitosis?
- Chromosome alignment and segregation.
- Partitioning of organelles between daughter cells.
- Definition of the site of cytokinesis.
What is the microtubules structure and it’s properties?
Microtubules are polarised hollow tubes made of tubular heterodimers.
Alpha is always at the minus end.
Beta is always at the plus end.
13 protofilaments make a microtubules.
The diameter of a microtubules is approximately 25nm.
What are accessory proteins?
They control the assembly of the cytoskeleton e.g. molecular motors.
Cytoskeletal systems are…
Dynamic and adaptable.
Microtubules…
- Star like array in interphase cell.
- Quickly rearrange to form bipolar mitotic spindle.
- Also form cilia and flagella.
- Also form bundles for transport.
- In plant cells, organised arrays of microtubules direct the pattern of cell wall synthesis.
Actin…
- Underly the plasma membrane in all animal cells.
- Provide strength and shape to the lipid bilayer.
- Form cell surface projections - lamellipodia and filopodia to sense the environment.
- Contractile ring during cell division.
- Muscle contraction.
- Stereocillia in inner ear tilt in response to sound.
- Microvilli on intestinal cells increase apical cell surface area.
Intermediate filaments…
- Line inner face of nuclear envelope to form protective cage for DNA: nuclear lamina.
- Cytosol form twisted cables to hold epithelial sheets together.
- Axon formation in nerve cells.
- Hair and fingernails.
The cytoskeleton is integral in differentiation by allowing asymmetric cell division. Give an example…
S. cervisiae - budding yeast.
Budding of the daughter cell needs the polar actin cytoskeleton. Actin cables and actin patches allow high polarity.
Actin patched become highly concentrated in the growing bud tip.
Actin cables align and point towards buds to allow secretion of a new cell wall and direct materials to the site of budding.
Overall polarised actin structures influence the orientation of the mitotic spindle.
Why are cytoskeletal filaments made up of small subunits?
- Allows rapid structural reorganisations.
2. Smaller components are able to diffuse in the cytoplasm.
What type of bonds form between cytoskeletal polymers?
Weak non-covalent interactions.
This allows rapid assembly and disassembly.
What allows the cytoskeleton to be dynamic?
- Small subunits.
2. Weak non-covalent interactions.
What do accessory proteins do?
- Convert signals into cytoskeletal action.
- Determine sites of assembly of filaments.
- Regulate construction of filaments.
- Change kinetics of filament assembly and disassembly.
- Harness energy to generate force and growth.
- Link filaments to organelles or the plasma membrane.
- Allow movement.
