Cytoskeleton Flashcards
The cytoskeletal system consists of 3 protein filament families including:
A. Kinesin, actin filaments, intermediate filaments
B. Actin filaments, microtubules, intermediate filaments
C. Microtubules, actin filaments, fubulin
D. intermediate filaments, actin filaments, myosin
E. Myosin, dynein, microtubules
B
Microtubules are composed of which monomers?
Alpha and beta tubulin
Microfilaments are composed of which monomers?
G-actin
Microfilaments bind what form of energy?
ATP
MTOC stands for?
Microtubule Organising Centre
Actin structures are assembed and disassembled rapidly, which of the following dictates this assembly and cell function?
A. Activity of MTOC in specific cellular locations
B. Location of cytoskeleton in the cell
C. Expression of microfilaments associated proteins in specific cellular locations
All of the above
C
Which of the following are involved in disassembly of actin filaments? A. Profilin B. Gelsolin C. Cofilin D. B & C
D. B & C
Profilin promotes
Actin assembly at positive end
Inhibits nucleation
Function of gelsolin
Sever actin filaments in half, to allow for quicker degradation
Arp2/3 regulated by..
Nucleiation proteins e.g. WASP
In the process called actin treadmilling:
A. Myosin proteins cause movement of actin filaments
B. Actin filaments of muscle cells contract
C. Subunits are added to the + end with the - end anchored to the membrane
D. Subunits are simultaneously added & removed from a filament
D
Microtubules serve all of the following functions in cells, EXCEPT:
A. They help to control movements of subcellular particles
B. They are the primary structural component of flagella
C. Microtubules mediate the movement of chromosomes during mitosis
Microtubules are the “thick filaments” of sarcomeres
Microtubules are components of centrioles
D
Which fibrous component(s) have dynamic instability? A. Actin filaments B. Microtubules C. Intermediate filaments D. A & B E. B & C
D
Why do intermediate filaments not have dynamic instability?
They are constructed for long-term use
Which of the following are involved in the disassembly of microtubules? A. Stathmin B. Katanin C. Tau D. Plectin
B. Katanin
Role of katanin
Cuts microtubules, allowing quicker disassembly
Role of tau
Bundles microtubules
Role of plectin
Links microtubules to intermediate filaments
Outline the action of taxol in anti-cancer
Stabilises microtubules, forcing the cell to be frozen in metaphase.
Rope-like filament structures formed from 8 protofilaments twisted together and does not have a molecular motor is a characteristic of what cytoskeleton system?
Intermediate filaments
During contraction of a sarcomere
A. Actin filaments are pulled towards the centre of the sarcomere
B. Kinesis head groups bind together
C. Ca++ is released from the cell through exocytosis
D. Microtubules slide relative to each other
E. None of the above
A
During contraction of a sarcomere
A. Actin filaments are pulled towards the centre of the sarcomere
B. Kinesis head groups bind together
C. Ca++ is released from the cell through exocytosis
D. Microtubules slide relative to each other
E. None of the above
A
During the contraction of a sarcomere, binding of ATP to myosin causes:
A. The myosin head group to bind to the actin filament
B. Release of the myosin head group from the actin filament
C. A change in the shape of myosin head group
D. Sliding of the actin and myosin filaments relative to each other
B
Which molecular motors allow intracellular transport on microtubules? A. Kinesin B. Myosin C. Dynein D. A & C E. None of the above
D
What is similar between focal adhesions and hemidesmosomes? A. They both use actin filaments B. They both use intermediate filaments C. They both use anchor proteins D. They both are very stable E. All of the above
C. They both use anchor proteins
What are the basic mechanisms of cell migration?
A. Triggered by signals from outside the cell
B. Actin-myosin based movement
C. Requires attachments to outside to pull agains
D. Ability to move all cell content
E. All of the above
E.
How many proteofilaments in a microtubule wall/ring?
13
Describe the structure of a microtubule.
Hollow tube with a wall consisting of 13 proteofilaments
Outline 4 functions of microtubules
Cytoplasmic:
- organisation and maintenance of animal cell shape and polarity
- chromosome movements
- intracellular transport, trafficking and movement of organelles
Axonemal: cell motility
Outline the 3 functions of cytoplasmic microtubules
Organisation and maintenance of animal cell shape and polarity
Chromosome movements
Intracellular transport, trafficking and movement of organelles
What is the function of axonemal microtubules?
Cell motility
What are the functions of microfilaments (actin)?
Muscle contraction Cell locomotion Cytoplasmic streaming Cytokinesis Maintenance of animal cell shape Intracellular transport/trafficking
Describe the structure of intermediate filaments
8 protofilaments joined end to end with staggered overlaps
Describe the structure of microfilaments
2 intertwined chains of F-actin
Outline the function of intermediate filaments
Structural support
Maintenance of animal cell shape
Formation of nuclear lamina and scaffolding
Strengthening of nerve cell axons (neurofilament protein)
Keeping muscle fibres in register (desmin)
How is actin polymerisation rate limited?
Trimer formation
Where is alpha actin found?
Muscle cells
Where is beta and gamma actin found?
Non-muscle cells
Actin filaments that are held together by the cross-linking protein fimbrin are not contractile. This is probably because:
A. fimbrin is a large protein that binds to several actin filaments and resists contraction.
B. the very tight packing of actin filaments by this small protein excludes myosin II filaments and other large proteins.
C. fimbrin arranges the actin filaments into gel-like networks in which myosin II activity does not produce contraction.
D. fimbrin arranges the actin filaments in parallel bundles in which all the plus ends point to the same direction.
E. the very weak cross-linking by this protein cannot convert myosin II activity into a coherent contraction.
B. The very tight packing of actin filaments by this small protein excludes myosin II filaments and other large proteins.
In lamellipodia, actin polymerization is nucleated by ...(1), while depolymerization is catalyzed by ...(2). A. (1) Arp 2/3 complex; (2) gelsolin B. (1) formin; (2) cofilin C. (1) formin; (2) gelsolin D. (1) Arp 2/3 complex; (2) cofilin E. (1) formin; (2) capping protein
D.(1) Arp 2/3 complex; (2) cofilin
In lamellipodia, actin polymerization is nucleated by ____ while depolymerization is catalyzed by ____.
Arp2/3 complex
Cofilin
In contrast to growing microtubules, shrinking microtubules:
A. have a GTP cap at their plus end.
B. have strong lateral interactions at their plus ends.
C. have curved protofilaments at their plus ends.
D. cannot be rescued unless microtubule-stabilizing proteins bind and inhibit depolymerization.
E. All of the above.
C. have curved protofilaments at their plus ends.
In which of the following structures are actin–myosin II bundles regulated by the troponin complex? A. Stress fiber B. Circumferential belt C. Contractile ring D. Adherens junction E. None of the above
E. None of the above
The gamma-tubulin ring is to microtubules what ____ is to actin filaments
Arp2/3 complex
Which of the following cytoskeletal filaments are abundant in an animal cell nucleus? A. Spectrin filaments B. Septins C. Intermediate filaments D. Microtubules E. Microfilaments
C. Intermediate filaments
Which cytoskeletal filaments are abundant in an animal cell nucleus?
Intermediate filaments
