BIOL 3800: EXAM 1
69 Cards in this Set
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which two cytoskeleton polymers use energy ? which uses what kind of energy?
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actin filaments: ATP
microtubules: GTP
intermediate filaments: none
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diameter of microtubules?
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25nm
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diameter of actin filament?
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7nm
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about how many protofilaments make up tubulin?
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~11-13 most of the time
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microtubules dont tread-mill, what do they do instead?
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have dynamic instability
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what two things can microtubules do physically?
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probe environment and push from a longer distance because they are thicker
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how are microtubules important in metosis?
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pulls chromosomes apart
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does ATP or GTP have more energy?
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have the same amount of energy
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a keratin is a kind of what?
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intermediate filament
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what physical properties do intermediate filaments have that is important?
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strong and stiff
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T/F: polymerization of intermediate filaments is easily reversible
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False
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what is the most common and most stable conformation of intermediate filaments?
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tetromer; the basic building block
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is assembly of intermediate filaments regulated?
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no, grow in every direction
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where is lamin located? what kind of filament is it?
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located in the nucleus, its a intermediate filament
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what causes lamin to disassemble during mitosis?
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phosphorylation
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what is the basic building block of microtubules?
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alpha and beta dimer
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what does the alpha and beta monomers use to bind?
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GTP
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which monomer, alpha or beta, hydrolyzes GTP in binding?
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alpha does the hydrolyzing, but never gets hydrolyzed itself because beta doesn't have the machinery to do it.
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does hydrolysis of GTP in microtubule monomers occur after or before polymerization?
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after
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what is the concentration of tubulin in the cell?
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10uM
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what is significant about GDP tubulin with its K- values?
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at the - and + ends, K- is very high, ~700-900. no other values can be measured.
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is tubulin affinity for eachother more or less than for actin? by how much?
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less, 10x less
actin K-: 1.4
tubulin K-: 44(+) and 23(-)
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why does GDP-tubulin 'catch up' with end of the filament?
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because K- is so much bigger in tubulin than actin, which makes GTP hydrolysis quick in comparison to the growth of the filament. also, there's a lower cellular concentration of tubulin.
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what happens structurally to tubulin polymer when GTP is hydrolyzed?
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the subunits splay out because of conformational change do to GTP hydrolysis
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in a life time plot of tubulin polymerization, what causes the 'catastrophe' evnets?
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the splaying of the filament due to mechanical stress from confromational changes in the relationship between alpha and beta subunits after hydrolysis of GTP
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what is the 'rescue' event in a life time plot of tubulin polymerization? how?
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regaining the GTP cap
luck of having unhydrolyzed GTP in the filament
enough association between GTP filaments occurs to make another cap
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what are the states of actin and myosin and a nucleotide during rigor in a muscle?
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actin and myosin tightly bound, no nucleotide bound
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when ATP binds to myosin, what happens?
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myosin and actin release eachother, myosin hydrolyzes ATP to ADP + Pi which lets the myosin head extend foward one actin monomer length.
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what happens when ADP+Pi myosin binds to n+1 actin?
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Pi is released which gives energy for the power stroke
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what is the 'power stroke' of myosin?
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when Pi is released from myosin by binding to n+1 actin the pulls the actin back
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after the power stroke what state is myosin and actin in with ADP bound instead of ATP?
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rigor
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what are the two microtubule motors?
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Kinesin and Dynein
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which microtubule motor moves in the + direction?
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Kinesin
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which microtubule motor moves in the - direction?
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dynein
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which microtubule motor is a large complex and which is myosin related?
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Kinesin: myosin related
Dynein: large complex
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In order for vesicles to bud from parent organelle to the target organelle what must happen?
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Polymerization of the solube protein complexes to form a proteinceous veicular coat
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cytoskeleton is composed of
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microfilaments, microtubules, and intermediate filaments
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microtubules are composed of
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tubulin dimers
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in alpha tubulin GTP ___. In beta tubulin GTP is_____.
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in alpha tubulin GTP is not hydrolyzed. In beta tubulin GTP is hydrolyzed
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Which end of a microtubule is favored for polymerization?
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the end with exposed beta subunits ( + end)
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alpha-tubulin
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Negative subunit that contains GTP, which it NEVER hydrolyzes; "depolymerization end"- requires higher Cc for polymerization and is slower than (+) end
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Nucleation phase
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G-actin subunits combine into short, unstable oligomers
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Elongation phas
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Rapidly grows with the addition of actin to both ends
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- Steady-state phase
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No net growth in the size of the F-actin filament
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Which end is polymerization fastest in?
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...
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Which end does polymerization faster at?
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polymerization occurs faster at the + end
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astral microtubule
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- associate with the mitotic spindle
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Kinetochore microtubule
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finds chromosomes, attaches, transports, reduces number of catastrophes
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polar microtubule
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pushing duplicated centrosomes apart
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kinesin-
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dimers. 14 classes, globular head binds ATP and microtubule, tail binds receptor on the cargo, moves from the – to + end
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dynein
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- large multimeric protein involved in retrograde transport (+ to – end), ATP dependent
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- actin (microfilament) based structures
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: microvilli, cell cortex, migrating cells, contractile ring
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- Myosin I
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= membrane association, endocytosis (anterograde transport)
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Myosin II
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= muscle contraction
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Myosin V
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= vesicular cargo transport
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- Myosin VI
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= endocytosis and movement toward the negative end (retrograde transport)
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S-phase
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-> chromosome duplication
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M-phase
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chromosomes are distributed to each daughter cell
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G1
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cell grows in size, synthesis of RNA and proteins required for DNA synthesis
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S-phase
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replication of the chromosome
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G2 phase
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end of S phase, cell prepares for mitosis
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M phase
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= mitosis and cytokinesis occur during this phase
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interphase=
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period of time between mitotic events. Nuclear envelope retracts into the ER. Golgi membranes breakdown into vesicles. Mitotic spindles form
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Prophase
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...
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prophase
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= mitotic aster separation. Chromosome condensation
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prometaphase
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= nuclear envelope dissolves. Attachment of kinetochore microtubules to kinetochores and beginning of congression
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- metaphase
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= chromosomes aligned at the metaphase plate
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Longest and shortest phases of cell cycle
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- synthesis phase of the cell cycle is the longest (10 hours). M phase is shortest (30 minutes)
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- cell cycle is controlled at key stages
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- cell will halt in late G1 phase
- G1 to S phase
- G2 to M phase
- within the M phase (metaphase to anaphase and anaphase to telophase)
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BIOL 3800: EXAM 1