Cytoskeleton Week 2 Flashcards
What is the cytoskeleton?
The skeleton and muscles of cells. It provides for architecture,shape and motility and for directed movement of organelles and molecules in the cell.
What are the components of the cytoskeleton?
Microtubules, Microfilaments, intermediate filaments and other accessory and regulatory proteins.
What is another name for microfilaments?
Actin filaments
What is the polymer of microtubulues?
Tubulin dimers (alpha and beta)
Tubulin is a ___________ meaning that is can turn _________ into __________
Tubulin is a GTPase meaning that it has the ability to turn GTP into GDP
How large is tubulin?
24nm
Where do microtubules stem from? What is the specific word to describe the orientation?
They stem out of the nucleus. Perinuclear
What are the accessory proteins associated with microtubules and what are their functions?
MAPs stabilize and space polymers and regulate interactions between cytoskeletal elements.
How dynamic are microtubules?
Highly dynamic if not stabilized
Microtubules act as a substrate for ___________
Microtubule based motor proteins to transport organelles. Think of the microtubules as the road and the motor proteins as cars.
Microtubules are ______________ which means that it has a ____ and ____ end. Which end is more dynamic?
Polarized , + and -. The + end lengthens and shortens more dynamically
What are the 5 functions of microtubules?
- Make up mitotic spindle
- Determine Cell Shape
- Provide railways for organelle transport
- Important for neuron cell shape and axonal transport
- Back bone for cilia and flagella
Which of the following are associated with microtubules?
Cilia, Flagella or Microvilli
Cilia and Flagella
Microtubules are composed of ___________ made of tubulin dimers. Describe this structure and how many are often found in a microtubule.
Protofilaments are stacks of tubulin dimers (alphabeta). Each microtubule has 13 +/- protofilaments.
What is used to determine the microtubule dynamic instability?
The behavior of the + end. Lengthening and shrinking is measured at the + end of the microtubule. When polymerization is occurring it is deemed “rescue” and when shortening is occurring it is called “catastrophe”.
Why does MT dynamic instability happen?
Tubulin, the dimer of microtubules, is a GTPase so it must be loaded with GTP prior to being polymerized. During elongation, a GTP-bound tubulins promote elongation and prevent the depolymerization of the microtubule. When the GTP-bound tubulin is hydrolyzed to GDP-bound tubulin, it removes this cap to promote shrinkage.
When does the GTP cap exist on microtubules?
During rescue or elongation
GDP-bound tubulin promotes elongation. Is this true or false?
False!
The ________ end of the microtubule is embedded in the nucleus.
Negative
_________ is negative end directed and ___________ is positive end directed. They both use ______ as energy.
Dynein, Kinesin, ATP
What are the two microtubule associated MOTOR proteins?
Dynein and Kinesin
What domain of motor proteins is attached to the mictrobule?
The head domain
____________ determines the type of cargo being carried by motor proteins and the rate of their activity.
Light and intermediate chains
What are examples of structural NON-MOTOR microtubule associated proteins?
Tau, MAP
What are the functions of non-motor microtubule associated proteins?
Organize MTs, Regulate MT stability and dynamics
What is nucleation?
The genesis of a cytoskeletal polymer
Where does nucleation of microtubules occur?
The centrosome.
__________ follows nucleation which is the elongation of the polymer
Polymerization
The centrosome is made of __________ perpendicularly aligned _________.
2 perpendicularly align gamma tubulins.
What is the purpose of gamma tubulins?
They are required for the polymerization of alphabeta tubulin dimers.
Where are gamma tubulins found in cells?
ONLY in the centrosome or other structures that nucleate, gamma tubulins are not part of the actual microtubule.
Cilia are located at ___________(organs). What is the function of cilia?
Lung epithelium, trachea and fallopian tube. They are mucociliary escalators which means they are found along airways to brush mucus out of the way.
Are cilia motile or non-motile?
They can be both!
The sperm tail is similar to __________. Why is this important?
It allows sperm to move towards the egg
Cilia and flagella do not originate from the nucleus. What is the nucleation site for cilia and flagella?
Basal bodies. Their negative end is in the plasma membrane as the positive end grows away from the cell.
Cilia and flagella are composed of ___________ in a __________ formation as _________. What is the name of this structure.
microtubules , 9+2 as doublets. Axoneme
___________ drives axonemal motility. Describe axonemal motility.
Dyenin allows for movement of the microtubule doublets in the axoneme structure to force the cilia and flagella to move.
________________ is a body-wide defect in axonemal structure that results in obstructive lung disease and __________. What structure is not functioning?
PCD/Immotile cilia syndrome, sterile males. The cilia is not functioning due to disruption in axonemal structure. This can prevent mucus from being removed from the lung epithelium and airways and also prevent sperm from traveling.
Combination of situs inversus and immotile cilia syndrome
Kartagener’s Syndrome; cilia are not functional during body development so cells move to wrong spots leading to irregular organ development.
How are microtubules being used to develop therapies for cancer?
Scientists are finding ways to disrupt microtubule dynamics to block cell division.
Mutations in _________ and _________ can result in smooth brain also known as ________.
L1S1 and doublecortin microtubule proteins, lissencephaly
What is Charcot-Marie Tooth syndrome?
It is a neuronal disease that has a mutation in kinesin.
How are neurodegenerative diseases related to microtubules?
Abnormalities or mutations in tau, dynein, kinesin and spastin
How can ________ viruses exploit a neuron’s microtubule based transport system to reach cell bodies?
Neurotropic
Virus will bind to the nerve ending of the cell to enter the body of the cell by catching a ride on a dynein motor protein towards the negative end of the neuron located in the cell body. Kinesin will then take replicated viruses back to the nerve ending to be transported to more cells for future replication.