Cytoskeleton & Cell Adhesion Flashcards
(52 cards)
How thick are microfilaments?
7nm
How thick are intermediate filaments?
10nm
What is the diameter of a microtubule?
25nm
What can microfilaments also be called? (2)
Actin filaments
F-actin
What are the subunits of microfilaments?
G-actin
What percentage of the total protein of the cell is comprised of microfilaments?
5%
How many subunits per complete turn of the microfilaments helix?
13 G-actin
What is the structure of a microfilament?
Polarised double helix
How long is one complete turn of the microfilament helix?
37nm
Why do microfilaments display polarity?
G-actin monomers are asymmetrical
What molecule is required for the growth of microfilaments?
ATP
On what end does microfilament growth/shortening occur fastest?
Plus end
What are the major functions of microfilaments? (3)
Mechanical support
Cell shape changes and maintenance
Cell motility
What do actin-sequestering proteins do?
Bind to G-actin to prevent polymerisation
What do capping proteins do?
Bind to ends of actin filaments to prevent growth (stabilisation)
What do motor proteins do?
Allow movement
What do cross-linking proteins do?
Hold actin cell cortex together
What kind of intermediate filaments are found in epithelia?
Keratin
What kind of intermediate filaments are found in neurons?
Neurofilamin/neurofilaments
What kind of intermediate filaments are found in nuclei?
Lamins
Where is the intermediate filaments network most dense usually?
Around the nucleus
What are the functions of intermediate filaments? (3)
Provide rigidity
Anchor cells at some junctions
Support nuclear structure (and protect/attach chromatin)
Describe the formation of intermediate filaments
One intermediate filament protein monomer = 2 intermediate filaments joined end-to-end
Two monomers come together to create a helical dimer
Two dimers combine = tetramer (fundamental unit)
Tetramers linked end-to-end in staggered formation
What are the subunits of microtubules?
One alpha-tubulin and one beta-tubulin