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True or False:
Both motor proteins (kinesin and dynein) contain intermediaries.
What are the intermediaries of kinesin and dynein?
Dynein: has dynactin that binds to the cargo and helps bind the motor protein to the microtubulue
kinesin: can have a variety of integral and peripheral membrane protiens
When does nucleation begin?
nucleation begins as alphabeta-tubulin dimers bind to an open ring of gamma-tubulin, which are held in place by a number of non-tubulin proteins that make up the large y-TuRC
Where does rapid transport occur?
What is involved?
- involved are organelles and vesicles
What type of work was done for rapid transport? On what?
work done on nerve axons
one type of technique for study is picking up the giant squid axon and squeezing the cytoplasm out of it onto a slide
___ are smaller than the __.
Rapid transport can happen in __.
any eukaryotic cell
What role does it play in development of plants?
- 1) determines the plane of division of plant cells
- 2) can help determine orientation of cellulose molecules in the cell wall
Determining the plane of division
1) What determines this?
- a band of microtubules that forms before the mitotic spindle forms called a preprophase band
- - this is parallel to the plane of division and determines the direction of the spindle, which will be perpendicular to the preprophase band
Determining orientation of cellulose molecules in the cell wall
- what does it provide information of?
- information in what direction the cells can enlarge
- - informed by enzymes in the cell membrane
- --rosettes of enzymes that are part of the membrane; movement of MT determines their orientation
- - causes oriented flow of material in membrane
What was the Gibbons experiment on?
chemical dissection of cilia from the protozoan Tetrahymena
What was the Gibbons experiment?
1) dissolved hte plasma membrane in digitonin and then immersed in a solution with EDTA, which removes divalent ions
2) when examined, the central tubules were missing, as were the arms from the A tubules; and the insoluble axonemes couldn't hydrolyze ATP, but the supernatant could
What happened when Gibbons mixed the insoluble axoneme (that couldn't hydrolyze ATP) with Mg2+?
much of hte ATP activity once again became associated iwth the axoneme
Difference between ciliary dynein and cytoplasmic dynein?
- Ciliary: three heavy chains
- cytoplasmic: contains two heavy chains
Explain when the cilium is straight and bent?
Straight: all the outer doublets end at the same level
Bent: cilium bending occurs when the doublets on the inner side of the bend slide beyond those on the outer side
Function of the outer kinetochore.
- microtubule binding
- microtubule motor activity
- signal transduction
function of inner kinetochore
- centromere replication
- chromatin interface
- formation of kinetochore
What is the function of Ndc80 complexes?
mediate attachment to the microtubule and kinetochore
What is the centrosome cycle of an animal cell?
1) G1: centrosome contains a single pair of centrioles that are no longer as tightly associated as they were during mitosis
2) S: daughter procentrioles form adjacent to maternal centrioles so that two pairs of centrioles become visible within the centrosome
3) G2: daughter procentrioles continue to elongate
4) Beginning of mitosis: centrosomes split, with each pair of centrioles becoming part of its own centrosome; as tehy separate the centrosomes organize the microtubule fibers that make up the mitotic spindle
APC^Cdc20 is responsible for what?
APC^Cdh1 is responsible for what?
destroying proteins like securin that inhibit anaphase, thus promoting the metaphase-anaphase transition
ubiquitinating protiens, like mitotic cyclins that inhibit exit from mitosis, promoting hte mitosis-G1 transition
Chromosome movement may be accomplisehd by a combo of what?
- poleward flux: moves the body of each microtubule towards one of the poles
- depoly of the microtubule at both ends:
The force required for chromosome movement may be provided by two things. What are they?
- 1) release of strain energy as the microtubule depolymerizes
- 2) motor proteins
When is the released energy utilized?
by the curled ends of hte depolymerizing protofilaments to bias the movement of hte bound heads of hte Ndc80 complex toward the minus end of the microtubule
Synthesis of plant cell wall macromolecules:
each rosette is thought to form a single microfibril that associates laterally with the microfibrils from other rosettes to form a larger fiber
the entire array of rosettes might move laterally within the membrane as it is pushed by the elongating cellulose molecuels
direction of movement is determined by oriented microtubules present in the cortical cytoplasm beneath the membrane