BIO 202 MIDTERM 3 CYTOSKELETON
QUESTIONS WITH CORRECT ANSWERS
2026-2027
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
2026-2027
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
