FInal 4 Flashcards
Provide mechanical strength in cells
IF
Used for cell locomition and cell surface shape
Actin
Determine position of organelles and direct movement
MTs
Specialized structures that increase absorptive surface area in epithelial cells
Microvilli
What kind of cytoskeletal material are nuclear lamina made from?
IFs
Cytoskeletal material used for flagella
MTs
Birthplace of all cytoplasmic MTs
MTOC
What are MTs protofilaments?
Polymers of alpha-beta tubulin heterodimers
Which subunit of MT does not cleave GTP to GDP?
Alpha
How many MT protofilaments assemble to form a tube?
13
What do actin monomers bind?
ATP
How many actin protofilaments intertwine to form a fiber?
2
What do two monomers of IFs form?
Coiled-coil dimer
What do two coiled-coil dimers of IFs form?
Staggered tetramer in an antiparallel arrangement
How many protofilaments of IFs twist into a ropelike filament?
8
What is the rate-limiting step for actin filament assembly?
Nucleation
What is the nucleation process of filament assembly dependent upon?
Concentration
Free actin and tubulin monomers are bound by what?
NTP
What happens when a GTP cap is lost?
MT will fray and shrink
Name for when MTs shrink due to loss of GTP cap
Catastrophe
MTs regrowing after a catastrophe
Rescue
What does taxol do to MTs?
Stabilizes them, essentailly killing rapidly dividing cells
Complex responsible for initiating MTs
gamma-TuRC
What end of MTs are inside MTOC
Negative
Complex responsible for initiating actin arrays
Arp2/3
Where do Arp2/3 usually nucleate?
PM
What angle do Arp2/3 bind to sides of existing actin filaments to form branches?
70
2 actin monomer binding proteins
Thymosin, profilin
Actin filament destabilizing protein
cofilin
Actin filament severing protein
Gelsolin
2 actin filament capping proteins
CapZ, tropomodulin
MT binding protein
Stathmin
MT filament binding protein
MAPs
2 MT filament destabilizer
Catasrophin, katanin
Actin-based motor
Mysoin
MT-based plus-end directed motor
Kinsein
MT-based negative-end directed motor
Dynein
WHat happens when myosin is treated with trypsin?
Heads and a small piece of tail are released from the tail
What happens when myosin is treated with papain?
Splits the heads up and removes the tail
Which myosin moves towards the minus end?
Mysoin Vi
What is the fastest motor protein?
Dynein
Which motor protein “walks”
Kinesin
While ____ binds tightly with bound NTP, ____ binds tightly without NTP
Kinesin, mysoin
One dimensional finger-like projection of actin
Filopodia
Two dimensional sheet-like structure of actin
Lamellipodia
Three dimenisional projections used for phagocytosis
Pseudopodia
3 extracellular stimuli receiving g-proteins that actin cytoskeleton responds to
Rho, Rac, Cdc42
Produces large numbers of actin stress fibers
Rho
Yields large numbers of filopodia
Cdc42
Generates very large lamellapodia that encircles the cell
Rac
How long is S-phase
10-12
Comittment to undergo another round of cell division
Start point (G1)
Key part of prophase
Chromsomes condense
Key part of prometaphase
Breakdown of nuclear envelope
Key part of metaphase
Chromosomes aligned at equator
Key part of anaphase
Chromosomes are being pulled apart
Key part of telophase
Chrosomes are at the poles
How is centrisome duplication triggered?
G1/S-Cdk complex
MTs that radiate in all directions
Astral MTs
Attach end-on to kinetochore
Kinetochore MTs
Span distance between bipolar spindle
Overlap MTs
Push overlap MTs against each other
Kinesin-5
PUll spindles towards each other
Kinesin-14
Attach chromosomes to MTs for positioning
Kinesin-4, Kinesin-14
Attach astral MTs to periphery and pull spindles apart
Dyneins
3 forces that move chromosomes on the spindle
Kinetochore generated poleward force, poleward MT flux, polar ejection force
What force is Anaphase A defined by?
Kinetochore generated poleward force and MT flux
What force is Anaphase B defined by?
SPindle poles move apart, dynein pulling on astral MTs
Visible pucker in PM during cytokinesis
Cleavage furrow
How do cleavage furrows form?
Contraction along actomyosin contractile ring
Region between future duaghter cells
Midbody
What is the organization and deposition of contractile ring regulated by?
RhoA
WHat kind of proteins are cyclin dependent kinases?
Serine/threonine kinases
4 classes of cyclins
G1/S, S, M, G1
Bind to Cdks at the end of G1 and commit the cell to DNA replication
G1/S cyclin
Bind to Cdks during S-phase and are required for the initiation of DNA replication
S-cyclin
Promote events of mitosis and G2/M transition
M-cyclins
Promote the passage through “start” point by helping govern G1/S cyclins
G1-Cyclins
2 steps of Cdk activation
Cyclin binding alters conformation of T-loop, CAK phosphorylates a threonine residue within T-loop
Inhibitory protein of Cdk
Wee1
Inhibitory protein of Wee1
Cdc25
General family of inhibitor proteins of Cyclin-Cdk
CKI (Cdk inhibitor)
Responsible for initiating S-phase by destruction of G1-Ss cyclins and CKIs
SCF
Responsible for initiating M-phase by destruction of M cyclins and regulators
APC/c
3 enzymes that function in series for attachment of ubiquitin
E1, E2, E3
What activates APC/C?
Cdc20
Initiate DNA replication once per cycle and ensures that every base of DNA is faithfully replicated once
S-Cdks
Where does DNA replication begin?
ORF
COmplex of initiator proteins that assembles on ORF during late mitosis
pre-RC
WHat does preRC mature into?
Preinitiation complex
What mediates preinitiation complex?
S-Cdks
First two molecules nucleates by ORC complex
Cdc6, Cdt1
What does S-cdk phosphorylate to allow replication machinery to work?
Cdc6
How is Cdt1 bound until it is liberated by S-Cdk
Geminin
What is geminin destoryed by?
APC/C
What are duplicated chromosomes held together by?
Cohesin
When triggers entry into mitosis?
Accumulation of M-cyclins
Phosphatase that removes the brakes on the regulatory factors stopping M-Cdk
Cdc25
What triggers siter-chromatid separation?
APC/C
Protein that uses negative feedback to block APC/C from initiating sister-chromatid separation
Mad2
How does the exit of mitosis occur?
Inactivation of M-cdk activity by APC/C degradation
