Cytoskeleton W2 Flashcards
What are the three classes of filaments
Microfilaments
Intermediate filaments
Micro tumbles
What are the roles of filaments in the cytoskeleton (4)
- Structure and support/mechanical stability
- intracellular transport
- cellular motility
- spatial organisation
Microfilament diameter
7nm
Intermediate filament diameter
10nm
Microtubules diameter
25 nm
What are microfilaments made of
Actin subunits arranged in a long spiral chain
Where are microfilaments found
Beneath cell cortex
2 properties of microfilaments
Dynamic
Have a plus minus end
Why are microfilaments dynamic
They rapidly polymerise and depolymerise
They grow and shrink via addition or removal of actin subunits
What happens at the plus end of a microfilament
Faster addition/removal of actin subunits
What happens at the minus end of a microfilament
Slower addition/removal of actin subunits
Microfilament roles in a cell(2)
Acts as a track for myosin motor motility
Enables cells to hold and move specialised shapes
Examples of microfilaments role in shape change and movement of a cell (2)
Involved in membrane pinching process in cell division
Formation of pseudopodia
What is pseudopodia
Eg microvilli
Are intermediate filaments more or less dynamic that microfilaments
Less
What is the role of intermediate filaments in the cell (2)
Stabilise organelle position
Support cell structure
What are intermediate filaments made from
Fibres: protein subunits vary
What are the protein subunits of intermediate filaments found in epithelial cells
Keratin
What are the protein subunits of intermediate filaments found in fibroblasts
Vimentin
Roles of microtubules (5)
Cell division
Intracellular organisation
Transport tracks for motor proteins to move cargo
Muscle contraction
Power flagella and cilia
What are microtubules made form
Long hollow tubules made from Polymers of tubulin
Microtubules - made from polymers of tubulin - polymers f tubulin made from ……..
Alpha and beta tubulin
What is a protofilament
Row of 10-15 alpha and beta tubulin that make up microtubules
Are microtubules directional
Yes
Microtubules are directional what does this mean
They have a + and - end
What is found at the negative end of a microtubule
Capping protein
Which end is the capping protein found on
What type of filament is r found on
Negative end of microtubule
How are microtubules organised
Via microtubule organising centres
Which end of microtubule is anchored in the microtubule organising centre
Minus end
What is the primary microtubule organising centre in a cell called
Centrosome
Where is the primary microtubule organising centre in a cell found
Near the nucleus
Examples of motor proteins (2)
Dynein
Kinesin
What are motor proteins
Proteins whose structure allows them to step along microfilaments or microtubules
What to motor proteins require to move
ATP
What blocks myosin binding sites at rests
Topomysin
What moves tropomysin during muscle contraction
Calcium ions
What does ATP do to myosin head
Detaches myosin head from myosin binding site
What does release of ADP and Pi do to myosin head
Attached it to binding site
What are flagella and cilia
Microtubule based projections of plasma membrane
What are flagella and cilia built up from
Microtubules and dynein
Filament role in disease (3)
Neurodegenerative disease
Cancer
Blistering skin disease
Filament role in neurodegenerative disease
Neurofibrillary tangles in Alzheimer’s disease
Filament role in cancer
Error in mitosis
Filament role in blistering skin disease
Epidermolysis simplex due to mutations in keratin
