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25 Cards in this Set

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  • Back
Which side of the microtubules are connected to the nucleus? to the periphery?
Negative charge to the Nucleus, Positive at Periphery
What is actin used for?
Cytoskeleton, filament control formation
What is critical to the separation of chromosomes? what is critical to cleavage of the cell?
Microtubules: separate chromosomes
Actin: cleave cell
Explain the dynamic equilibirum in protein molecules regarding assembly/disassembly of filaments? Are filaments dynamic?
Equilbirum between small soluble subunits and filamentous polymers and yes they are dynamic
What does Actin use to form? What does microtubules use to form?
Actin: ATP
Microtubules: GTP
Actin filaments will preferentially add and lose at what ends?
Positive-add, negative-lose
But it's a continual adding and subtracting
Explain how actin is formed
G-actin (ATp, subunits form dimers, and a helix is formed, positive and negative end, respective preferential add/lose
What happens if the GTP at the leading edge is hydrolyzed in microtubules? How is this fixed?
Hydrolyzed=plus end becomes unstable::rapid and catastrophic loss of dimers from plus end, resulting in shrinkage

In order to prevent total loss: the GTP container dimers must be restored, allowing for elongation of protofilament
What conformational change occurs when GTP is hydrolzyed?
Protofilaments will bend and dimers will be lost
How are protofilaments made? How many are in one microtubule?
Protofilaments are made from alpha and beta tubulin,requiring GTP for assembly. The plus end of the protofilament is the end exposed. 13 protofilaments make one microtubule
How are intermediate filaments made?
Coiled coil dimers are formed, twisting together in a staggered pattern to form a filament. staggered tetramer of two coiled coil dimers are formed with opposing head to tail links (carboxy to amino)
What is the predominant INTERMEDIATE FILAMENT SUBUNIT in skin? What happens in genetic defects?
Keratin. Mutations can lead to weakening of keartin filaments, resulting in mechanically stressed skin with cells tearing along the basal lamina (as the hemidesmosome and desmosome attachments are strong)
Which are the largest filaments? Smallest? Middle?
Largest: microtubules, then intermediate filament, then microfilament actin
Where are gamma tubulin found? Which end is stabilized?
Centrioles. Minus end is stabilized to allow plus end to extend out (gamma ring complex surround centrioles, where the tubulin grows out of)
What is Arp? Explain the assembly of the Arp complex, and the actin meshwork
Protein-modified actin filaments (actin related proteins)

Activation of Arp2/3 will form a complex. The complex will bind to the minus end of the actin, stabilizing the minus end, and the filament will grow rapidly.

Arp complexes can also be used to form actin meshworks, as the active Arp complex can nucleate a new actin FILAMENT TO FORM tadaaa (angle 70 degrees)
Formin. Explain it.
Modifying protein that a cell can use to help form ACTIN FILAMENTS, walks up filament as it assembles
Profilin. Explain it.
Can help form ACTIN. Binds to monomer, and ENHANCES binding of ATP to actin
Describe the multiprotein actin filament forming machine in regards to formin and profilin
Formin whiskers have profilin bound to them, profilin has actin monomers bound to them. This complex binds actin and sticks it onto the plus end of the filament. Like a robot with wiggly arms placing things on it's head.
How does cofilin modify actin?
Causes filament to rotate a smaller distance (tighter) making the distance reduced form one helix to next
CapZ protein. Talk about it.
Caps minus end of actin filaments, which allows the filament to grow longer at the SAME CONCENTRATION OF MONOMERS wow.
What are some of the different ways actin filaments are bundled in the cell?
Stress fiber--contractile bundle (mechanical stress)
Cell cortex--gel like network (mesh)
Filopodium--tight parallel bundle
How is myosin II related to actin?
Myosin II is a molecular motor used by the cell to create FORCE, based off the protiens (i.e. actinin or fimbrin) between actin filaments determines if myosin II will enter bundle to bind to actin (way for cell to control)
What's in a microvillus?
Actin is tightly packed in there, with myosin I,
How are microtubules related to neurons?
MTs are needed to transport cellular material from cell body to synapse
Talk about Tau. What happens in Alzheimers?
Tau is a protein bounded to microtubules in the axon, it allows MTs to be packed into a tighter bundle.

In Alzheimers, it has been noted that hyperphosphorylated Tau protein is present, where Tau binds to each other instead of MT to form Tau filaments