Section 4 Flashcards
What is the cytoskeleton made of ?
Microtubules, microfilaments, intermediate filaments
What are microtubules made of?
Tubulin
What are microfilaments made of?
Actin
What kind of bonds form the cytoskeleton and why are these bonds beneficial to this structure?
Non-covalent, because they an be easily broken and the cytoskeleton must be readily able to assemble and disassemble
What are the functions of the cytoskeleton?
Determines cell shape, keeps organelles in the correct positions, directs movement (acts as a track), and is involved in mitosis and cell division
What is the diameter of a microtubule?
25 nm
How many protofilaments makes up a microtubule?
13
What is tubulin formed of?
Tubulin is a heterodimer formed of alpa and beta tubulin, in an alternating layout.
How thick are protofilaments?
4 nm
What kind of proteins are alpha and beta tubulin?
Both are GTP binding proteins
What polarity are beta and alpha tubulin?
Beta = positive, alpha = negative
What are the functions of microtubules?
Mechanical support, maintains intracellular organization, movement of intracellular components, as well as cell movement
What are MAPs?
Microtubule Associated Proteins
What are the two types of MAPs?
Dynamic and Structural
What are the names of some Structural MAPs?
MAP 1,2,4 and tau
What do structural MAPs do?
Increases stability of microtubule and promotes microtubule assembly, influences cross-linking
What are the names of some dynamic MAPs?
Kinesin and Dynein
What is the function of dynamic MAPs?
Direct intercellular movement by hydrolyzing ATP which changes chemical energy to physical energy.
Describe the conformation of Kinesin
Heterotetramer, 2 heavy chains, 2 light chains
Head, stalk, tail, neck
Which domain of kinesin is the motor?
The head
Which domain of kinesin binds to the microtubule?
The head
Which domain of the kinesin undergoes a conformational change?
Neck and stalk
What do the light chains of kinesin bind to ?
Vesicles and particles
Which end of the microtubule does kinesin move towards?
PLUS END
What causes movement of kinesin?
Hydrolyzing ATP, induces a conformational change
Which kinesin moves in the opposite direction than the rest of the kinesin?
Kinesin 14
Which region of dynein binds to the microtubules and how?
The heavy chains, they have little microtubule binding stocks attached to them
Which region of dynein binds to ATP?
The head
What does the microtubule organizing center (MTOC) do?
nucleates and initiates mictorubule assembly (assembles tubulin into microtubules)
What happens to microtubules when the temp is increased?
Assembly
What happens to microtubules when temp is decreased?
Disassembly
Which end of the microtubule incorporates GTP into it?
Plus
Which end of the microtubule does dynein travel towards?
MINUS end
What allows for quick assembly and disassebly of a microtubule?
GTP hydrolysis and incorporation into the microtubule
How large are intermediate filaments in diameter?
10 nm
What are the functions of intermediate filaments?
provide mechanical strength
How big are microfilaments in diameter?
6-8 nm
What is the function of microfilaments?
important for internal movement and movement as a whole, shape determination, and structure of cell projections
What is the main structural protein of microfilaments?
Actin
What is co-polymerization?
When 2 similar but not identical monomers form a polymer with each other
What kind of actin is the monomer?
globular actin (g actin)
What is treadmilling?
When assembly at plus end is equal to the disassembly at the minus end
What are the 2 different arrangements of microfilaments?
Bundle and Network
What is a cortex?
An area of bundled microfilaments
What is the function of the cortex?
involved in injestion of particles, process of extension, and cell division
What is the function of bundles?
Support
What is the function of networks?
movement
What is an actin binding protein?
A protein that binds to actin
What is Arp 2/3?
Actin related protein complex that promotes actin trimers. It interacts with other proteins and nucleates assembly (similar to gamma tubulin)
What is a monomer sequestering protein?
A protein that prevents polymerization (blocks a monomer from becoming a part of a polymer)
What is an end capping protein?
A protein that caps other proteins, regulates microfilament length
What is Monomer Polymerizing actin binding protein?
A protein that promotes polymerization of actin to microfilaments
What is profilin?
A protein that promotes the removal of ADP from actin filaments and replaces it with ATP. Makes assembly more likely to occur
What is depolymerizing actin binding proteins?
Bind to microfilaments at the end and break down the filaments
What is a cross linking protein?
A protein with 2 actin binding sites, extended and flexible
What is villin?
A cross linking protein that reduces flexibility by bundling
What is a filament severing protein?
a protein that binds to the sides of the microfilaments and break the filaments into smaller bits
what are Membrane binding actin binding proteins?
Proteins that bind to the membrane and actin
What is the general function of actin binding proteins ?
control assembly rate, number and length of spatial pattern, interactions of cells with one another, and substrates around the cells
True or False: Actin polymerization can cause movement through the cell
true
What is cofilin?
A protein that attaches to the minus end and is a disassembly associated protein
What is vinculin?
form focal complexes or adhesions, present on lamellipodium
What are integrins?
Integral membrane proteins that attach to things outside the cell
