Regulation of Animal Cell Shape Flashcards
what are Cytoskeleton
- Helps maintain cell shape
- helps position the organelles within the cells
- it rapidly disassembles and reassembles
- allows for rapid changes in cell shape
- is highly dynamic but still provides stability
what are the 4 main components of the cytoskeleton
- microtubules (25nm)
- Microfilaments (7nm)
- intermediate filaments (8-12nm)
what are microtubules
- are composed of tubulin subunits
- have alpha and beta particles
- resists compression, resulting in helping maintain the cell shape
- they may radiate out from an organizing center
- can also provide cell motility
what are the names of the 2 motions
1) flagella: ‘snake-like’ motion (sperm)
2) cilia: ‘rowing-like’ motion
if the cell are fixed in place what makes them move
- cilia moves the fluid past them through beatings
microtubules are also involved in what other motility within the cell
- organelle motility
- ATP-powered motor proteins can ‘walk’ organelles along microtubules
- allows vesicles, or other organelles to be transported to specific targets within the cell
what are microfilimants
- are double chain of actin subunits
- they form linear strands, and 3-d networks (using branching proteins)
- resist tension
- the cortical network under the plasma membrane helps make this region less fluid and this maintains the cell shape
what interactions between actin support cell movement
- motor proteins –> myosin
what does actin-myosin interactions allow
- muscle contraction
amoeboid movement
cytoplasmic streaming in plants
what are intermediate filaments made of
made of various proteins: keratins, lamins, neurofilaments
describe intermediate filaments (what they look like etc)
- supercoiled into ‘cables’
- less dynamic than microtubules or microfilaments
- they form relatively permanent cellular structure
- good at resisting tension
- they may also remain after the cell that made them has died, e.g hair and out layer of skin
what do intermediate filament help with
- maintaining cell shape
- anchoring organelles
what are the 3 major types of cell junctions
- tight
- desmosomes
- gap
describe the tight junctions
- hold neighboring cells tightly pressed together
- may form a continuous seal
- prevents movement of fluid across cell layers
describe desmosomes
- anchoring junction
- provide attachment between sheets if cells
- act like rivets
- connected into the cell by intermediate filaments
describe what a gap junction is
- a point of cytoplasmic contact between 2 cells
- ions and small molecules can pass from cell to cell
- allows rapid cell to cell (intercellular) communication
how are cell joined together
- the extracellular matrix
describe the extracellular matrix
- the ECM is composed of material secreted by cells
- this secretion occurs by constitutive exocytosis
- most ECM proteins are glycoproteins
what are most abundant ECM glycoprotein called
- is collagen
- collagen fibres have great tensile strength
where do you find the collagen fibres
- are embedded in a proteoglycan complex matrix
what are proteoglycans, and what do they do
- are proteins with extensive sugar additions
- they trap water within the ECM
- water resists compression and thus helps retains tissue shape
what other glycoproteins attach cells to the ECM
- Fibronectins
what membrane proteins connect the ECM to the cytoskeleton
- Integrins
what does the fibronectins and integrins provide from the ECM to the cell interior
- a communication link from ECM to the cell interior
