Cell motility Flashcards
What does cell motility require?
- energy
- guidance
- mechanical interaction with something out the cell
- swimming vs crawling
- microtubules vs actin microfilaments
Describe what is required for cells to swim?
microtubules
Describe what is required for cells to swim?
actin microfilaments
What are microtubules composed off?
hollow tubes of a & b tubulin (they alternate)
- 13 protofilaments
- has intrinsic polarity due to the 2 tubulin subunits
What is the structure of microtubule-based motility?
Cilia & Flagella
Where is flagella used in cells?
sperm/ protozoa
Where is cilia used in cells?
respiratory tract/reproductive tract
What is the difference between cilia & flagella?
they have the same structure, but they have different lengths:
cilia - 2-10 x 0.25um
flagella - 100-200 x 0.25um
What is larger - cilia or flagella?
flagella (10 times larger)
What is the major functional structure of the cilia & flagella?
Axoneme
What is the microtubular arrangement of the axoneme?
9+2 microtubule assembly
Describe the 9+2 microtubule assembly composition
- 9 outer doublets
- Radial spokes
- Inner pair
How many protofilaments do complete (A) fibres have?
13 protofilaments
How many protofilaments do incomplete (B) fibres have?
10
What is dynein arms?
the motor protein in microtubules
What links the 2 central doublets?
Dynein - the presence of ATP allows sliding of microtubules (in separate directions)
What are the 2 dynein arm-dependent functions?
Inner arm - waveform
Outer arm - power
What is the transition zone?
where flagella/cilia meets the plasma membrane
What is the function of basal bodies?
cell motility
What happen if actin acts on a muscle?
moves organism
What happen if actin acts on a non-muscle?
moves cells/tissues
Does an actin monomer have polarity?
Yes
What is in the middle of an actin subunit?
bound nucleotide (ATP)
What can occur to the ATP molecule in the middle of a G actin filament?
It can be hydrolysed released energy and leaving ADP
What can occur to the GTP in microtubules?
can be converted to GDP
What is actin treadmilling?
addition of actin at one end, while removing at the other end also occurs.
What is larger - an actin filament or microtubule?
Microtubule
What is the difference in the nucleotide in actin vs microtubule?
Actin - ATP
Microtubule - GTP
What does profilin (actin-binding protein) inhibit?
profilin inhibits nucleation
What regulates actin dynamics?
Accessory proteins
What does profilin bind to?
ATP actin
Describe how actin-based motility works?
Filopodium - narrow projections
Lamellipodium - broader projections of membrane
Stress fibres - quite static - transmit force & allow cell to be contractile
Cortical actin ring - around edge of cell
