BIO 202 MIDTERM 3 CYTOSKELETON
QUESTIONS WITH CORRECT ANSWERS
2025-2026
Cytoskeleton CORRECT ANSWER organized network of polymers within a cell;
scaffold- like appearance; mechanical strength; drives cell division and movement
Three cytoskeletal elements CORRECT ANSWER intermediate filaments, microtubules, actin
filaments
intermediate filaments CORRECT ANSWER
form dense network inside cytoplasm; made of fibrous intermediate filament proteins
intermediate filament subunit CORRECT ANSWER staggered antiparallel tetramer of two
coiled- coil dimers; dimers slightly offset; n-termini stick out at each end
intermediate filament function CORRECT ANSWER
provide structural support to cells; enable cells to withstand mechanical stress
types of intermediate filaments CORRECT ANSWER cytoplasmic and nuclear
keratin filaments CORRECT ANSWER
cytoplasmic; distribute stress when skin is stretched; anchored to plasma membrane to provide structur
e to cells
nuclear filaments CORRECT ANSWER support and strengthen nuclear membrane
actin filaments CORRECT ANSWER polymers composed of protein actin; highly dynamic
actin filament subunit CORRECT ANSWER
single copy of protein actin; monomers assemble in two strand helix
, actin filament functions CORRECT ANSWER
organized in linear bundles or more complex networks; essential for many cell movements and cytokine
sis during cell division
microtubules CORRECT ANSWER hollow cylinders made of tubulin heterodimers; highly dynamic
microtubules functions CORRECT ANSWER
create tracks on which vesicles, organelles, and other cellular components are transported; form mitotic
spindle to segregate chromosomes prior to cell division; present in cilia
microtubules subunit CORRECT ANSWER heterodimer composed of a- and
B- tubulin; formed through non-covalent protein-protein interactions
microtubules polymers CORRECT ANSWER
heterodimers assemble into protofilaments; lateral interactions between protofilaments (13) form tube
What filaments have polarity? CORRECT ANSWER
actin and microtubules; have asymmetric subunits (plus and minus ends)
Why would you want filaments to have polarity? CORRECT ANSWER
can serve as tracks for transport; motor proteins can walk these tracks in specific direction; cells exploit
dynamic properties to perform certain essential functions
Assembly of actin filaments steps CORRECT ANSWER nucleation, elongation, steady state
nucleation CORRECT ANSWER formation of stable nucleus of three subunits; slow
elongation CORRECT ANSWER monomer addition on both ends; fast; faster on plus end
steady state CORRECT ANSWER rate of addition equal to rate of loss
QUESTIONS WITH CORRECT ANSWERS
2025-2026
Cytoskeleton CORRECT ANSWER organized network of polymers within a cell;
scaffold- like appearance; mechanical strength; drives cell division and movement
Three cytoskeletal elements CORRECT ANSWER intermediate filaments, microtubules, actin
filaments
intermediate filaments CORRECT ANSWER
form dense network inside cytoplasm; made of fibrous intermediate filament proteins
intermediate filament subunit CORRECT ANSWER staggered antiparallel tetramer of two
coiled- coil dimers; dimers slightly offset; n-termini stick out at each end
intermediate filament function CORRECT ANSWER
provide structural support to cells; enable cells to withstand mechanical stress
types of intermediate filaments CORRECT ANSWER cytoplasmic and nuclear
keratin filaments CORRECT ANSWER
cytoplasmic; distribute stress when skin is stretched; anchored to plasma membrane to provide structur
e to cells
nuclear filaments CORRECT ANSWER support and strengthen nuclear membrane
actin filaments CORRECT ANSWER polymers composed of protein actin; highly dynamic
actin filament subunit CORRECT ANSWER
single copy of protein actin; monomers assemble in two strand helix
, actin filament functions CORRECT ANSWER
organized in linear bundles or more complex networks; essential for many cell movements and cytokine
sis during cell division
microtubules CORRECT ANSWER hollow cylinders made of tubulin heterodimers; highly dynamic
microtubules functions CORRECT ANSWER
create tracks on which vesicles, organelles, and other cellular components are transported; form mitotic
spindle to segregate chromosomes prior to cell division; present in cilia
microtubules subunit CORRECT ANSWER heterodimer composed of a- and
B- tubulin; formed through non-covalent protein-protein interactions
microtubules polymers CORRECT ANSWER
heterodimers assemble into protofilaments; lateral interactions between protofilaments (13) form tube
What filaments have polarity? CORRECT ANSWER
actin and microtubules; have asymmetric subunits (plus and minus ends)
Why would you want filaments to have polarity? CORRECT ANSWER
can serve as tracks for transport; motor proteins can walk these tracks in specific direction; cells exploit
dynamic properties to perform certain essential functions
Assembly of actin filaments steps CORRECT ANSWER nucleation, elongation, steady state
nucleation CORRECT ANSWER formation of stable nucleus of three subunits; slow
elongation CORRECT ANSWER monomer addition on both ends; fast; faster on plus end
steady state CORRECT ANSWER rate of addition equal to rate of loss
