The Cytoskeleton Flashcards
Major Functions of Cytoskeleton
- provide structural support
- the microtubular filament provides internal organization of cell such as vesicle transport and organelle organization
- Actin and microtubules assist in cell division
- Actin filaments assist with large scale cell movement
What are the different microscopy techniques that can be used to look at the cytoskeleton
Light microscopy (cannot see cytoskeletal filaments)
Fluorescence microscopy (used to detect proteins)
Transmission electron transport (reveals detailed structures)
What is Immunofluorescence microscopy used or?
To look at the location of proteins in a cell
They only used fixed cells
Place a primary antibody on the protein and then a secondary antibody attaches to the first one and has a tagged fluorescence
What are intermediate filaments
these are medium sized filaments that provide structural support
Different types of intermediate filaments
Cytoplasmic IF which provide mechanical strength in animal cells to help deal with the mechanical stress that cell experiences
Nuclear filaments give the nuclear laminate its shape and it is formed by lamina
Describe the structure of these IFs
- A-helical monomer with an n and c-terminus. It is polar
- 2 monomers pack together to form a coiled coil dimmer that still has polarity
- 2 diners form a tetramer and due its composition, it is difficult to decipher if the two sides are polar, therefore at this point forward there will be no more polarity
- 8 tetramers form into a filament. This filament will tough and able to bear a lot of stress when pulled, meaning it won’t break
Example of IF in Epithelial cell
Keratin filaments form of a network throughout the cytoplasm
They are anchored by cell-cell junctions, specifically desmosomes
Important to note that they do not cross these anchors to neighboring cells
What are microtubules
They are the largest filaments and assist in an organizing function in all eukaryotes
They assist in cell organization such as vesicle transport and the filaments form the mitosis spindle
Describe the structure of microtubules
they are long, hollow tubes
These tubes are made from individual subunits of b-GTP and a-GTP which attach to form a protafilaments and 13 protofilaments will form a hollow tube
The tube will have polarity as the B end is the plus end and a-side is minus
Dynamic instability
The filament will undergo rapid extension if GTP hydrolysis is slower than the addition of an-tubular dimer
This growth will form a GTP-cap
Shrinking happens when GTP hydrolysis is faster than the addition of T-form heterodimers
During this process,the GTP-Cap is lost and now instead of T-form, you have D-form heterodimer which will fall off due to weaker bonds
How do ab-heterodimers bond to each other and other heterodimers
The individual subunits will bond to each other non-covalently. These bonds are the strongest compared to bonding between protofilaments
What is the site where microtubules grow
Microtubules organization centre (MTOCs)
The minus end will be stabilized by the MTOC and the plus end will grow
The centrosome is an example of a MTOC
Function of MTOC
They have nucleating sites where they start assembling new microtubules
Example of nucleating site
Y-tubular ring complex (y-TuRC)
There is a ring of y-tubulan that acts as an attachment site for ab-tubulin dimers
How are microtubules used in intracellular transport
The microtubules plus end will be stabilized to prevent dynamic instability and they will act as a transport passage for motor proteins to move neurotransmitters along to the axon terminal
The vesicle will be attached to a motor protein which will walk along the microtubule to reach its destination
