BIOL 370 - MT 1 Questions with
complete solution 2025/2026
How do animal cells generate movement? - correct answer ✔cytoskeleton through a protein-based
intracellular network and motor proteins which are enzymes that use energy from ATP
Four general types of cellular movement - correct answer ✔amoeboid movement, motor proteins
walking, motor proteins pulling, motor proteins and cytoskeleton
amoeboid movement - correct answer ✔reorganization of the cytoskeletal network, growth of the
cytoskeleton in one region of the cell pushes membrane outward
how do walking motor proteins cause cellular movement - correct answer ✔walk along relatively fixed
elements of the cytoskeleton to transport cargo throughout the cell
how do pulling motor proteins cause cellular movement - correct answer ✔motor proteins attached to
the cell membrane pull on the cytoskeleton, moving an element of the cytoskeleton
how do motor proteins and the cytoskeleton work together to generate cellular movement - correct
answer ✔they are arranged so that they slide over each other, pulling the cell into a different shape
what comprises the cytoskeleton - correct answer ✔microtubules, microfilaments, and intermediate
filaments
microtubules - correct answer ✔long hollow tubes composed of repeating units of tubulin which is a
dimer of alpha and beta tubulin, they typically grow at the + end and shrink at the - end
how do microtubules form? - correct answer ✔alpha tubulin and beta tubulin combine to form a dimer
which assemble end to end, many of these form a sheet which rolls into a tube
,how is microtubule length regulated? - correct answer ✔GTP bound to beta tubulin is hydrolyzed to
GDP after polymerization which weakens the binding affinity of tubulin, favouring depolymerization
(results in dynamic instability)
what factors influence the rate of growth and shrinkage of microtubules? - correct answer
✔concentration of tubulin (above or below a critical conc.) whether or not GTP bound by beta tubulin is
hydrolyzed, microtubules associated proteins (MAPS) and temperature
MTOC - correct answer ✔microtubule organizing centre, typically where microtubules grow from as
typically the - end is located there while the + end extends towards the cell membrane
how does concentration of tubulin affect the growth rate of microtubules - correct answer ✔because
they form spontaneously (due to polarization), they will grow more if the concentration is greater, and
want to shrink more if it is lower (essentially tread-milling effect)
Treadmilling of actin - correct answer ✔ADP-bound actin comes off the minus end, while only ATP-
bound actin is added to the plus end. The net result is a process called treadmilling.
kinesin - correct answer ✔a motor protein that moves towards the plus end of a microtubule
dynein - correct answer ✔a motor protein that moves towards the minus end
why are there multiple motor proteins attached to a vesicle in vesicle movement? - correct answer
✔because if one leg is not attached, the entire protein will float off, so there are multiple proteins
attached to a vesicle at a time because if one floats off the vesicle can still be moved
microfilaments - correct answer ✔Long, thin fibers of polymerized beta-actin (forming filamentous-
actin) that function in the movement and support of the cell and are polymers of the protein actin
, how does microfilament movement arise? - correct answer ✔actin polymerization and the sliding
filament model using myosin
f-actin growth - correct answer ✔spontaneous and is driven by polarity
what factors influence the rate of growth and the rate of shrinkage of microfilaments - correct answer
✔concentration of G-actin and capping proteins which increase length by stabilizing the minus end
__________ movement is produced by polymerization of actin - correct answer ✔amoeboid
myosin - correct answer ✔motor protein, specifically an ATPase that transforms the energy associated
with ATP hydrolysis into mechanical energy (containing three distinct regions of a head, tail and neck)
what is the directionality of myosin movement? - correct answer ✔most myosin forms move towards
the + end of an actin filament except myosin VI (plays role in intracellular transport and endocytosis)
what are two aspects to remember about proteins when considering the sliding filament model? -
correct answer ✔proteins change shape when compounds bind to them and changing shape can allow
proteins to bind or unbind other compounds
what are the stages of the cross-bridge cycle - correct answer ✔ATP binds to a myosin head causing
myosin to detach, this causes ATP to be hydrolyzed to ADP and P which remain bound by myosin.
Hydrolysis causes myosin to extend and attach to actin which causes phosphate to be released,
promoting the power stroke (actin moves and myosin becomes more kinked). ADP is released and ATP
binds, causing myosin to detach. (Draw out and write out stages)
unitary displacement - correct answer ✔distance myosin steps during each cross-bridge cycle, this is
due to the structure of myosin and the periodicity of the actin filament (because it is a dimer). For
myosin monomers the amount movement is variable.
complete solution 2025/2026
How do animal cells generate movement? - correct answer ✔cytoskeleton through a protein-based
intracellular network and motor proteins which are enzymes that use energy from ATP
Four general types of cellular movement - correct answer ✔amoeboid movement, motor proteins
walking, motor proteins pulling, motor proteins and cytoskeleton
amoeboid movement - correct answer ✔reorganization of the cytoskeletal network, growth of the
cytoskeleton in one region of the cell pushes membrane outward
how do walking motor proteins cause cellular movement - correct answer ✔walk along relatively fixed
elements of the cytoskeleton to transport cargo throughout the cell
how do pulling motor proteins cause cellular movement - correct answer ✔motor proteins attached to
the cell membrane pull on the cytoskeleton, moving an element of the cytoskeleton
how do motor proteins and the cytoskeleton work together to generate cellular movement - correct
answer ✔they are arranged so that they slide over each other, pulling the cell into a different shape
what comprises the cytoskeleton - correct answer ✔microtubules, microfilaments, and intermediate
filaments
microtubules - correct answer ✔long hollow tubes composed of repeating units of tubulin which is a
dimer of alpha and beta tubulin, they typically grow at the + end and shrink at the - end
how do microtubules form? - correct answer ✔alpha tubulin and beta tubulin combine to form a dimer
which assemble end to end, many of these form a sheet which rolls into a tube
,how is microtubule length regulated? - correct answer ✔GTP bound to beta tubulin is hydrolyzed to
GDP after polymerization which weakens the binding affinity of tubulin, favouring depolymerization
(results in dynamic instability)
what factors influence the rate of growth and shrinkage of microtubules? - correct answer
✔concentration of tubulin (above or below a critical conc.) whether or not GTP bound by beta tubulin is
hydrolyzed, microtubules associated proteins (MAPS) and temperature
MTOC - correct answer ✔microtubule organizing centre, typically where microtubules grow from as
typically the - end is located there while the + end extends towards the cell membrane
how does concentration of tubulin affect the growth rate of microtubules - correct answer ✔because
they form spontaneously (due to polarization), they will grow more if the concentration is greater, and
want to shrink more if it is lower (essentially tread-milling effect)
Treadmilling of actin - correct answer ✔ADP-bound actin comes off the minus end, while only ATP-
bound actin is added to the plus end. The net result is a process called treadmilling.
kinesin - correct answer ✔a motor protein that moves towards the plus end of a microtubule
dynein - correct answer ✔a motor protein that moves towards the minus end
why are there multiple motor proteins attached to a vesicle in vesicle movement? - correct answer
✔because if one leg is not attached, the entire protein will float off, so there are multiple proteins
attached to a vesicle at a time because if one floats off the vesicle can still be moved
microfilaments - correct answer ✔Long, thin fibers of polymerized beta-actin (forming filamentous-
actin) that function in the movement and support of the cell and are polymers of the protein actin
, how does microfilament movement arise? - correct answer ✔actin polymerization and the sliding
filament model using myosin
f-actin growth - correct answer ✔spontaneous and is driven by polarity
what factors influence the rate of growth and the rate of shrinkage of microfilaments - correct answer
✔concentration of G-actin and capping proteins which increase length by stabilizing the minus end
__________ movement is produced by polymerization of actin - correct answer ✔amoeboid
myosin - correct answer ✔motor protein, specifically an ATPase that transforms the energy associated
with ATP hydrolysis into mechanical energy (containing three distinct regions of a head, tail and neck)
what is the directionality of myosin movement? - correct answer ✔most myosin forms move towards
the + end of an actin filament except myosin VI (plays role in intracellular transport and endocytosis)
what are two aspects to remember about proteins when considering the sliding filament model? -
correct answer ✔proteins change shape when compounds bind to them and changing shape can allow
proteins to bind or unbind other compounds
what are the stages of the cross-bridge cycle - correct answer ✔ATP binds to a myosin head causing
myosin to detach, this causes ATP to be hydrolyzed to ADP and P which remain bound by myosin.
Hydrolysis causes myosin to extend and attach to actin which causes phosphate to be released,
promoting the power stroke (actin moves and myosin becomes more kinked). ADP is released and ATP
binds, causing myosin to detach. (Draw out and write out stages)
unitary displacement - correct answer ✔distance myosin steps during each cross-bridge cycle, this is
due to the structure of myosin and the periodicity of the actin filament (because it is a dimer). For
myosin monomers the amount movement is variable.
