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60 Cards in this Set

  • Front
  • Back
Actin filaments:
7-8 nm
Made of actin
25 nm
Made of tubulin
Intermediate filaments
10 nm
heterogenous components
Myosin filaments
size varies
made of myosin
What are all of these filaments?
Cytoskeletal filaments
What is the structure of microtubules like?
A tube
What are microtubules made of?
Alpha and beta tubulin which form heterodimers
How are a/B tubulin dimers arranged?
As protofilaments
What is the building block of the microtubule?
The heterodimer of a/B tubulin
How many protofilaments in a microtubule wall?
How do microtubules form?
By selfassembly - even in a test tube.
What is required for microtubules to self-assemble?
-Critical concentration of heterodimers
-physiological conc of salts
What is a unique feature of microtubules?
How can the polarity of microtubules be seen?
By the fact that they have different rates of assembly at each end.
At which end of the microtubule is association fastest?
Plus end - the on rate
What happens at the minus end?
Dissociation - the off rate
What is the phenomenon of heterodimers passing from the plus end to the minus end called?
What regulates the assembly / disassembly of microtubules?
the local concentration of GTP
How does GTP affect microtubule assembly?
It is essential for assembly at the plus end - if it's not there dissassembly will occur.
What happens when a heterodimer binds to a microtubule?
GTP is hydrolyzed
What happens when the rate of assembly exceeds the rate of GTP hydrolysis?
A gtp cap is formed and stabilizes the microtubule
What happens when the rate of heterodimer addition slows?
The cap is lost and the microtubule depolymerizes rapidly.
What does the rapid association and dissassociation of MT's illustrate?
That they have DYNAMIC INSTABILITY - regulated locally by the GTP concentration.
What makes MTs unstable?
When GDP-bound heterodimers in the interior catch up to the GTP cap and cause hydrolysis
Where in the cell cycle are microtubules very important?
In mitosis - they make up the bipolar mitotic spindle.
When do mitosis spindle microtubules form and disintegrate?
Form - during metaphase
Deform - after cell division
What are some anticancer drugs that interfere with MTs work?
By binding spindle microtubules and either preventing disassembly or disrupting them.
List 4 anticancer drugs that target microtubules:
Where are the dynamic properties of the mitotic spindle particularly evident?
-Rapidly dividing tissues
What are Microtubule organizing centers?
Sites where polymerization of microtubules is organized or initiated.
microtubule organizing center
What are the 2 principle MTOCs?
Basal bodies
What are centrioles functional in?
Organization of the mitotic spindle
Where are centrioles found?
In the centrosome
Where are Basal bodies?
At the cell surface where cilia extend
How do MTOCs function?
By establishing uniform polarity of microtubules relative to other organelles
What end of MTs is associated with microtubules?
The minus end
What do the structures of centrioles and basal bodies consist of?
Microtubule TRIPLETS
How many triplets are in a centriole?
What is gamma tubulin?
A molecule structurally related to alpha and beta tubulin but it does not form tube structures.
What is gamma tubulin found as?
Part of y tubulin ring complex
What is the function of the gamma tubulin ring complex?
Initiation of polymerization at MTOCs
What exactly does the y tubulin ring complex do?
Caps the minus end of microtubules to prevent their disassembly
What microtubule based organelles are found on most cell surfaces?
Cilia and flagella
What are functions of cilia and flagella?
What is the cytoskeletal component of a cilia/flagella?
What does the axoneme consist of?
9+2 pattern - pair of normal MTs in the center, 9 outer doublets
What do axonemes arise from?
Basal bodies
What is the structure of a basal body like?
9 triplets arranged in a circle - just like centrioles
So what are the two MTOCs?
Centrioles and Basal bodies
-9 triplets arranged in a circle
What is a major function of MTs in neurons?
What type of motility is accomplished with MTs?
-Ciliary bending
-Organelle translocation
What are the motors that move stuff along MT tracks?
Dynein and Kinesin
How do Dynein/Kinesin function as motors?
By using ATP
What is the motor for ciliary bending?
How does Dynein cause ciliary bending?
By causing relative sliding between microtubules within the axoneme
What type of motility is caused by cytoplasmic dynein or kinesin?
Motility on single cytoplasmic MTs - i.e. axonal transport
In what direction along MTs does
-Kinesin move?
-Dynein move?
Kinesin: towards the pos end
Dynein: towards the neg end
How many ATPases are on each motor?
What is the movement of stuff along dynein and kinesin similar to?
Crossbridge cycling of myosin