Chapter 16: Cytoskeleton Flashcards
This cell structure is dynamic, adaptable, and made up of individual units to form large structures
cytoskeleton
What is the basic function of the cytoskeleton
spatial and mechanical function
What are the 3 protein families/filaments components of a cellular cytoskeleton
- intermediate (keratin)
- microtubules
- microfilaments (actin)
What are 3 functions of cytoskeletal accessory proteins
- link and anchor filaments
- control filament assembly
- motor protein function
These cytoskeletal components twist into tight cables to provide mechanical strength and sheer resistance
intermediate filaments (keratin)
Where are intermediate filaments (keratin) found in the cell?
- nuclear lamina
- epithelial sheets via desmosomes
- Cytosol
What are the 3 functions of intermediate filaments (keratin)?
- stabilize epithelium sheets
- aid in axonal extension
- form nails and hair
These cytoskeletal components form hollow tubes that determine the position of organelles within a cell
microtubules
What are 3 functions of microtubules (other than organelle positioning)
- motor protein guides
- form mitotic spindles
- form locomotive structures (flagella/cillia)
In what organisms are microtubules found?
ALL eukaryotes
What are the microtubule subunits?
- alpha tubulin
- beta tubulin
This microtubule subunit has exposed GTP in the heterodimer to allow for lengthening; this is also what determines the “plus” side
beta tubulin
What two features of microtubule locomotive structures (flagella and cilia) allow for whip-like movement?
- dynein arms
- nexin proteins
This protein allows microtubule structures to slide against one another to produce shifting movement
dynein arms
This protein connects microtubule structures in cilia and flagella to allow for bending when tubules slide against eachother
nexin proteins
These filaments are present in ALL eukaryotic cells to aid in whole cell locomotion
microfilaments (actin)
What are the functions of actin filaments?
- whole-cell locomotion
- form cell surface projections
What are 4 locations where microfilaments (actin) are found?
- lameliopodia + filipodia
- stereocilia hair cells
- cytokinetic contractile rings
- muscle cells
What energy source do actin filaments use to polymerize?
ATP/ADP
What are the two forms of microtubule/microfilament subunits?
T “nTP” and D “nDP”
What end of microtubule/microfilament polymers is easier to polymerize? and why?
plus end! has available reactive nTP
at what point does polymer treadmilling occur in cytoskeletal elements?
when the [actin monomer] is between the T and D critical concentrations
at what point will a loss of filament subunit occur
when the D critical concentration is below the T Cc
at what point does filament polymerization occur?
when the T Cc is less than the D Cc
This is a complete loss of the nTP cap in a polymerized cytoskeletal element that leads to rapid shrinkage
catastrophe
This is a regain of the nTP cap in a polymerized cytoskeletal element that leads to rapid growth
rescue
What happens to a straight microtubulin protofilament after a catastrophe (GTP–>GDP)
creates a curved protofilament (forms hollow tube)
About how fast can individual microtubule molecules diffuse?
1-2 seconds
what cytoskeletal elements are highly conserved and present in ALL eukaryotic cells?
actin and microtubulin
Microtubule formation is sourced from what cellular structure?
centrosome
