microtubules and actin microfilaments Flashcards
what does cell motility need
-Energy
-Guidance
-Mechanical interaction with something outside the cell
-Swimming vs Crawling
-Microtubules vs Actin Microfilaments- 2 skeletal structures
what are microtubules made up of
-Hollow tubes of a and b tubulin
-hollow structure makes it rigid
-a microtubule cross section is 24nm and has 13 protoflaments with alternating alpha and beta tubulin
whats the motility of a microtubule like
-Structure:
=Cilia and flagella
-Cargoes:
=Of cells: protozoa, sperm
=Of fluids: respiratory, reproductive tract
whats cilia movement like in the trachea
-moves back and forward
whats The Axoneme
-Major functional structure
-9+2 microtubule assembly
-9 outer doublets
-Inner pair
-Radial spokes- protein structure holding axoneme together
Cilia and Flagella Structure
-Same structure in cilia and flagella
-Different length:
=Cilia: 2-10(long) x 0.25 μm (across)
=Flagella: 100-200 x 0.25 μm
-Major functional structure = The Axoneme
-Different Waveforms
-Dynein arm-dependent functions: Inner arm: Waveform, Outer arm: Power
whats The Outer Doublets
-Dynein Arms- motor proteins that works with microtubules to enable motion
-Complete (A) Fibres 13 protofilaments
-Incomplete (B) Fibres 10 protofilaments- piggy backs off the alpha fibres
how does Dynein And Sliding
-dynein- anchored to one microtubule and adjacent microtubule
-also helps microtubules to slide past each other
-anchored 2 microtubules helps prevent a sliding motion and turns into an anchored motion
-ATP as the energy source
whats Nexin Crosslinkers
-contains:
=inner dynein arm
=nexin
=outer dynein arm
=radical spoke
=inner sheath
=central singlet microtubule
=plasma membrane
=microtubule A and B= outer double microtubule
-normal flagellum= dynein causes microtubule bending
The Axoneme in Full
-outer doublet and inner pair
-plasma membrane
-basal body- anchor and start point of microtubule/ axoneme structure
-transition zone- point at which axoneme meets cell and basal body
-2 flagella
whats the basal bodies
-9 x 3 microtubule array - 9 groups and triplets, nothing in middle
-0.2 um x 0.4 um (diameter x length)
-Basal body «< CENTRIOLE»_space;> Centrosome
whats Actin-based Motility like
-Muscle-Moves Organism (using skeletal muscles and actin)
-Non Muscle- Moves Cells/Tissues
-Motility From Motors and Turnover
what do actin filaments use for energy
-ATP-> ADP+Pi
-actin filaments have a plus and minus end
whats the structure of microtubules
-GTP used for microtubules not ATP
- negative end of microtubule doesnt grow quickly and is stable
-positive end of microtubule grows fast
Actin Filaments vs Microtubules
-Feature. Actin Filment Microtubule
Diameter 5-9 nm 24 nm
Form Solid Hollow
Subunits Homomeric a/b Heterodimer
Subunit size 42 kDa 50 kDa
Amino acids 375 450
Nucleotide in monomer ATP GTP
Nucleotide in filament. ADP GTP/GDP(a)/(b)
whats the actin treadmill
-adding monomers at one end and disassembling monomers at the other end
-actin circle back to growing end therefore actin treadmilling
whats actin-binding proteins
-profilin inhibits nucleation
-profilin binds to ATP actin
-accessory proteins regulate actin dynamics
-severing action of cofilin
1) monomer nucleating
2) monomer sequestering
3) end-blocking (capping)
4) monomer polymerising
5) depolymerising
6)bundling
7)flamnet-severing
8) membrane- bounding
difference between Cilia/flagella and Cytoskeleton/muscle
-Cilia/flagella- filament = microtubule, motor= dynein
-Cytoskeleton/muscle- filament= actin, motor= myosin
whats Myosin Structure
-coiled coil of 2 alpha helices
-c-terminus
-n-terminus
-connects to actin at one end
whats Actin-based motility like
-Filopodium- narrow pointing projections therefore more flexible
-Lamellipodium- wave of cells moving forward
-Stress fibres-actin filaments in the body of a cell used for tension- has an aligned structure
-Cortical actin
