Pollev, quiz questions, hw questions

Why is membrane fluidity important for membrane function?

below a membranes transition temperature, proteins in the membrane are no longer flexible enough to function

Which of the following types of protein would be most easily removed from a membrane by changing pH or ionic strength?

peripheral proteins

Which of the following is NOT a function or a characteristic of biological membranes?

Phospholipids are not major constituents of membrane structure.

Membranes provide a means of cell-to-cell communication.

Membranes contain receptors for the detection of external signals.

Membranes regulate the movement of substances into and out of the cell.

Phospholipids are not major constituents of membrane structure.

Each of the following is a type of cell - cell junctions except

tight.

plasmodesmata.

adhesive.

gap.

All are cell - cell junctions.

All are cell - cell junctions.

Each of the following is typical characteristics of an integral membrane protein transmembrane segment except

20−30 amino acids long.

α-helical structure.

amphipathic.

composed primarily of hydrophobic amino acids.

All are characteristics of a typical transmembrane segment.

amphipathic

A scientist is investigating the properties of two different biological membranes that have different amounts of cholesterol in them. Which of the following would accurately describe the membrane that has more cholesterol compared to the membrane with less cholesterol in it?

The membrane with more cholesterol will have increased fluidity at low temperatures and lower fluidity at high temperatures compared to the membrane with less cholesterol.

The two membranes will have the same degree of fluidity at all temperatures.

The membrane with more cholesterol will have decreased fluidity at low temperatures and lower fluidity at high temperatures compared to the membrane with less cholesterol.

The membrane with more cholesterol will have increased fluidity at all temperatures compared to the membrane with less cholesterol.

The membrane with more cholesterol will have increased fluidity at low temperatures and lower fluidity at high temperatures compared to the membrane with less cholesterol.

In response to temperature changes, cell membranes change state to become more solid or more fluid by undergoing

differential scanning calorimetry.

a phase transition.

transverse diffusion.

membrane folding.

lipid raft formation.

a phase transition

Each of the following is true about homeoviscous adaptation in membranes except

may decrease the average length of membrane lipid fatty acid tails.

may increase the unsaturation of membrane lipid fatty acid tails.

may increase the proportion of cholesterol in animal cell membranes.

maintains membrane viscosity despite changes in environmental temperature.

occurs primarily in homeothermic (warm-blooded) organisms and only rarely in poikilothermic (cold-blooded) organisms.

occurs primarily in homeothermic (warm-blooded) organisms and only rarely in poikilothermic (cold-blooded) organisms.

The most common number of carbons in fatty acid hydrocarbon chains of membrane phospholipids is

7.

10.

16.

19.

24.

16

Which of the following experimental data would suggest the presence of a transmembrane protein?

The protein has windows of the primary sequence with positive hydropathy values separated by windows of the primary sequence with negative hydropathy values.

The protein isolates with the membrane fraction of the cell rather than the cytoplasmic fraction of the cell.

The primary sequence contains stretches of polar and nonpolar amino acids, suggesting an amphipathic design.

All of the other answer choices suggest the presence of a transmembrane protein.

All of the other answer choices suggest the presence of a transmembrane protein.

Which of the following types of protein would be most easily removed from a membrane by changing pH or ionic strength?

fatty acid-anchored protein

integral protein

GPI-anchored protein

peripheral protein

glycosylated integral protein

peripheral protein

Which of the following is true about glycosylated plasma membrane proteins?

The carbohydrate usually is one sugar and rarely more than 5 sugars long.

Carbohydrate is added only after the protein is in the plasma membrane.

The carbohydrates can be detected experimentally with ferritin-linked lectins.

N-linked carbohydrates are linked to hydroxyl groups in protein R groups.

Only one specific site is glycosylated on each protein.

The carbohydrates can be detected experimentally with ferritin-linked lectins.

Most cells have a negative plasma membrane potential (Vm) because they have

an excess of negatively charged solute molecules inside the cell.

an excess of water molecules inside the cell.

equal concentrations of ions on both sides of the membrane.

an excess of negatively charged solute molecules outside the cell.

an excess of positively charged solute molecules inside the cell.

an excess of negatively charged solute molecules inside the cell.

Which of these molecules CANNOT enter a cell by simple diffusion?

glucose

carbon dioxide

water

ethanol

glucose

Phosphorylation of glucose following its transport into a cell

decreases glucose transport into the cell by decreasing its concentration gradient across the plasma membrane.

targets the glucose for transport back out of the cell.

converts glucose into a form that can more easily be exported from the cell.

increases glucose transport into the cell by increasing its concentration gradient across the plasma membrane.

maintains a higher level of glucose outside the cell.

increases glucose transport into the cell by increasing its concentration gradient across the plasma membrane.

Which of the following is a characteristic of facilitated diffusion (passive transport) of a molecule across a membrane?

The rate of transport is saturable.

The direction of transport is determined by concentration and/or electrochemical gradients.

It is highly specific for the molecule being transported.

Its rate is higher than that of simple diffusion of the molecule.

All of the above are true.

All of the above are true.

Each of the following is an example of facilitated diffusion except

glucose transport by GLUT1.

aquaporin transport.

chloride-bicarbonate exchange.

oxygen transport.

ion channel transport.

oxygen transport.

Active transport is the protein-mediated movement of substances __________.

in response to membrane potential

coupled to ATP synthesis

toward thermodynamic equilibrium

against the concentration gradient of that substance

against the concentration gradient of that substance

Each of the following is a characteristic of active transport mechanisms except

coupling transport of a solute down its concentration with transport of another solute up its concentration gradient via a symport or antiport mechanism..

sensitivity to inhibitors such as proton pump inhibitors.

moving solutes away from equilibrium across a membrane.

nondirectionality for moving a solute in either direction across a membrane depending on the solute concentration gradient.

coupling a thermodynamically unfavorable (endergonic) process with a favorable (exergonic) process.

nondirectionality for moving a solute in either direction across a membrane depending on the solute concentration gradient.

The primary difference between active transport and facilitated diffusion is that active transport is the only one of the two in which

the mechanism is not saturable.

the S concentration gradient provides the energy necessary for S transport.

transporter proteins are required.

the direction of transport is [S]low → [S]high.

the direction of transport is [S]high → [S]low.

the direction of transport is [S]low → [S]high.

Each of the following is true for the mechanism of the Na⁺/K⁺ ATPase pump except

the E2 conformation is open to the outside of the cell and has high affinity for K+.

K+ triggered dephosphorylation of the pump stabilizes the E2 conformation.

the E1 conformation is open to the inside of the cell and has high affinity for Na+.

Na+ triggered phosphorylation of the pump stabilizes the E2 conformation.

Each E1-E2 cycle pumps 3 Na+ ions out and 2 K+ ions in.

K+ triggered dephosphorylation of the pump stabilizes the E2 conformation.

Which of the following accurately describes the driving force and directionality of the nonactive transport of all molecules across the membrane?    

The membrane potential drives transport in a direction related to the charge of the molecule.

pH drives molecule movement according to the charge of the molecule.

the movement toward equilibrium for those substances

Osmosis of water drives molecule movement toward the hypertonic side.

the movement toward equilibrium for those substances

Which of the following molecules can enter cells by diffusion in the absence of a transporter protein?

oxygen and carbon dioxide

How is facilitated diffusion similar to active transport?

both involve specific transport proteins

Each of the following is a function of membranes except

Question 1 options:

	A. cell - cell communication
	B. information storage
	C. defining cell and organelle boundaries
	D. sites for specific biochemical functions

B. information storage

Which of the following would be the most thermodynamically unfavorable membrane lipid activity in a membrane?

Question 2 options:

	A. lateral diffusion
	B. rotation
	C. association with a neighboring lipid
	D. transverse diffusion

D. transverse diffusion

How is an ion’s electrochemical potential related to its concentration gradient?

Question 3 options:

	A. The electrochemical potential is a specialized type of concentration gradient.
	B. The electrochemical potential is a component of the concentration gradient.
	C. The concentration gradient is a component of the electrochemical potential.
	D. The concentration gradient is cancelled out by the electrochemical potential.

C. The concentration gradient is a component of the electrochemical potential.

What kind of protein could help a plant that had been dried out too much by exposure to the sun?

Question 4 options:

	A. a glucose transporter to help remove extra sugar from photosynthesis
	B. an aquaporin to help cells take up more water
	C. an ATPase to help generate more energy for water uptake
	D. a and c

B. an aquaporin to help cells take up more water

Which of the following is an example of indirect active transport?

Question 5 options:

	A. Na+/K+ ATPase
	B. aquaporin water transport
	C. Na+/glucose symport
	D. glucose permease transport

C. Na+/glucose symport

Which event triggers the creation of an action potential?

The membrane depolarizes above a certain threshold potential

What role do voltage-gated calcium cation channels play in the transmission of signal across synapses?

they enable an influx of calcium to trigger neurotransmitter secretion.

Which of these statements best describes the Nernst equation and the resting membrane potential?

The Nernst equation can predict whether an ion is in electrochemical equilibrium across a cell membrane if the resting membrane potential is known.

The Nernst equation can be used to calculate the resting membrane potential.

The Nernst equation is irrelevant to the resting membrane potential.

The Nernst equation can predict net ion movement based on the ion's membrane permeability.

The Nernst equation can predict whether an ion is in electrochemical equilibrium across a cell membrane if the resting membrane potential is known.

Plasma membrane permeability of which of the following ions is most important in generating the resting membrane potential?

potassium ions

calcium ions

sodium ions

chloride ions

None of the above generates resting membrane potential.

potassium ions

Sodium channels are concentrated in the

dendrites and synaptic boutons.

axon hillock and nodes of Ranvier.

dendrites and nodes of Ranvier.

dendrites and axon hillock.

synaptic boutons and axon hillock.

axon hillock and nodes of Ranvier.

With respect to an action potential, which of these statements is the most relevant regarding its direction of propagation?

The myelin sheath prevents charge leakage, allowing the current to move in only one direction.

Dendrites contain a high density of sensitive voltage-gated sodium channels that initiate an action potential.

The neuronal voltage-sodium channel has a refractory period following activation.

The membrane potential change generated by influx of ions propels the action potential until the Na+/K+ pump can restore balance.

The neuronal voltage-sodium channel has a refractory period following activation.

Which answer shows the correct order of occurrence during an action potential?

depolarizing phase, hyperpolarizing phase, repolarizing phase, resting state

hyperpolarizing phase, depolarizing phase, repolarizing phase, resting state

resting state, depolarizing phase, repolarizing phase, hyperpolarizing phase

resting state, hyperpolarizing phase, depolarizing phase, repolarizing phase

resting state, depolarizing phase, repolarizing phase, hyperpolarizing phase

At which point in the graph do voltage-gated potassium channels open?

C

Each of the following is a correct relationship between action potential phase and channel status except

repolarizing phase; K+ channels open.

repolarizing phase; Na+ channels closed.

hyperpolarizing phase; K+ channels open.

depolarization; Na+ channels open.

hyperpolarizing phase; Na+ channels open.

hyperpolarizing phase; Na⁺ channels open.

What is the role of calcium at the synaptic terminal?

Depolarization of the synaptic terminals by an invading action potential opens voltage-gated calcium channels at the terminal, thus permitting diffusion of calcium out of the synaptic terminal.

Calcium, like sodium, is out of both ionic and electrical equilibrium. Therefore, it counteracts the loss of free energy following depolarization of the synaptic terminal.

Calcium enters the synaptic terminal, permitting water to enter, increasing hydrostatic pressure, and forcing neurotransmitter out of the terminal into the synapse.

Depolarization of the synaptic terminals by an invading action potential releases intracellular calcium stores or allows calcium channels to open to allow calcium to enter the synaptic terminal from the extracellular environment, thus permitting neurotransmitter release.

Depolarization of the synaptic terminals by an invading action potential releases intracellular calcium stores or allows calcium channels to open to allow calcium to enter the synaptic terminal from the extracellular environment, thus permitting neurotransmitter release.

While characterizing the activities of several neurons, you find a neuron with the following properties:
(1) When stimulated, the neuron fails to release neurotransmitters into the synaptic cleft.
(2) Microinjection of calcium ions calcium ions has no effect on the neuron. (In other neurons, such microinjection stimulates the t-SNARE and v-SNARE complex interaction that promotes neurotransmitter secretion.)
The abnormality in this neuron is most likely associated with the function of

gap junctions.

the vesicle membranes.

acetylcholinesterase.

GABA receptors.

synaptotagmin.

synaptotagmin

You have added a specific amount of excitatory neurotransmitter mixed with a 6× higher concentration of an inhibitory neurotransmitter to a synaptic cleft. You expect that the postsynaptic neuron will

show a net depolarization as a result of neuronal integration.

produce 6× its normal number of action potentials.

show a net hyperpolarization as a result of neuronal integration.

not respond to either signal.

produce 6× its normal number of negative action potentials.

show a net hyperpolarization as a result of neuronal integration.

Which of these is the second of the three stages of cell signaling?

transduction

Epinephrine acts as a signal molecule that attaches to _____ proteins.

G- protein linked receptor

Compounds that inhibit receptors by preventing the natural messenger from binding are known as

arrestins.

syndecans.

antagonists.

sildenafils.

agonists.

antagonists

Base your answer to this question on the following information:

You have isolated a primary signal factor from the blood of a space alien, which you name XFF (for X-files factor). You also have isolated various types of alien cells which appear to interact with XFF. Based on preliminary data, you think that XFF could be similar to one of three compounds normally found in human blood: epidermal growth factor (EGF), epinephrine, or estrogen.


You add a large amount of XFF to cultured alien liver cells. Which of the following would confirm that XFF is the alien equivalent of human epinephrine?

insensitivity to insulin

increased glucose uptake

glycogen breakdown

decreased cell division

increased cell division

glycogen breakdown

You recently identified a molecule that you believe is a primary messenger for a signal transduction mechanism. All you know about this ligand is that it is hydrophilic. Where would you expect to find initial interaction of the molecule with its receptor?

on the cytoplasmic side of the plasma membrane

in endosome vesicles

within the cytoplasm of the cell

on the outer surface of the plasma membrane

within the nucleus of the cell

on the outer surface of the plasma membrane

Which of the following represents a "molecular switch" that activates G_α proteins?

GTP hydrolysis

the binding of ATP

exchange of GDP for GTP on Gα

exchange of GTP for GDP on Gα

exchange of GDP for GTP on G_α

Each of the following is a step in the epinephrine - cAMP pathway in which the signal is amplified except

G-protein activation of adenylyl cyclase.

protein kinase A phosphorylation of target proteins.

receptor activation of G-protein.

adenylyl cyclase production of cAMP.

G-protein activation of adenylyl cyclase.

Each of the following is a characteristic of calmodulin except

It can activate specific kinases and phosphatases.

It has a very high affinity for calcium ions, and binds calcium ions irreversibly.

It binds two calcium ions at each end of the protein.

When activated by calcium ion binding, it wraps around proteins that have calmodulin binding sites.

All are characteristics of calmodulin.

It has a very high affinity for calcium ions, and binds calcium ions irreversibly.

The concept of receptor affinity does not apply only to the original receptor and ligand. For which of the following pairs of interacting molecules in signal transduction would a change in affinity of one for the other NOT affect how they work in signal transduction?

receptor tyrosine kinase/phosphate

protein kinase A/cAMP

calmodulin/calcium

G protein alpha/GDP

receptor tyrosine kinase/phosphate

Base your answer to this question on the following information:

You have isolated a primary signal factor from the blood of a space alien, which you name XFF (for X-files factor). You also have isolated various types of alien cells which appear to interact with XFF. Based on preliminary data, you think that XFF could be similar to one of three compounds normally found in human blood: epidermal growth factor (EGF), epinephrine, or estrogen.


Which of the following would best be used to demonstrate XFF is most like EGF?

exposure of cells to ryanodine

exposure of cells to tyrosine kinase inhibitors

microinjection into cells of nonhydrolyzable GTP analogues

receptor binding assays

exposure of cells to radioactive XFF

exposure of cells to tyrosine kinase inhibitors

Each of the following is a characteristic of hormones except

synthesis by endocrine tissue cells.

having a hormone-specific lifespan in the blood ranging from seconds to hours.

secretion directly into the bloodstream.

interacting with specific receptors on cells in target tissues throughout the body.

All are characteristics of endocrine hormones.

All are characteristics of endocrine hormones.

Each of the following ligands binds to an intracellular receptor except

retinoic acid.

thyroid hormone.

cortisol.

estrogen.

epinephrine.

epinephrine

1. Which of the following lists best represents cells that have a membrane potential?

A. Muscle cells, but not nerve cells or epithelial cells
B. Muscle cells and nerve cells, but not epithelial cells
C. Muscle cells, nerve cells, and epithelial cells
D. None of the above

C. Muscle cells, nerve cells, and epithelial cells

2. What is the function of the inactivating particle of a voltage-gated sodium channel?

A. To prevent a nerve impulse from traveling in two directions instead of in just one
B. To increase the voltage amount needed to reach an action potential
C. To require new protein synthesis to replace used sodium channels and thus prevent neurons from firing too much
D. To provide a mechanism for potassium and sodium channels to create the right resting membrane potential

A. To prevent a nerve impulse from traveling in two directions instead of in just one

3. If you compare a neuron with an electrical wire, with what does the myelin surrounding the axon correspond?

A. Conductive copper wire
B. Plastic insulating coating
C. Solder
D. None of the above

B. Plastic insulating coating

4. Which of the following would be correctly described as a juxtacrine signaling?

A. A signal that requires physical contact between cells
B. A signal that acts on the cell that produces it
C. A signal that diffuses over long distances from the producing cell
D. A signal that diffuses over short distances from the producing cell

A. A signal that requires physical contact between cells

5. The low level of cytosolic calcium ions in unactivated cells is established by which of the following?

A. Calmodulin
B. Calcium ATPases
C. Kinases
D. Phosphatases

B. Calcium ATPases

If the concentration of tubulin monomers is above the critical concentration of the plus end but below the critical concentration of the minus end, what will happen to in vitro microtubule assembly?

Response recorded

A The microtubules will get longer.

B The microtubules will get shorter.

C The microtubules will lose subunits off both the plus end and the minus end.

D Treadmilling will occur

treadmilling will occur

Which of the following sentences describes characteristics shared by all myosins?

Response recorded

• They are motor proteins that bind to GTP.

• They are motor proteins that are active in muscle cells.

• They are motor proteins that carry vesicles during intraflagellar transport. (microtubule based mobility)

• They are motor proteins that bind to and exert force on microfilaments.

• They are motor proteins that bind to and exert force on microfilaments.

During the course of muscle contraction the potential energy stored in ATP is transferred to potential energy stored in _____.

the myosin head

the myosin tail

the thin filament

actin

the myosin head

A researcher extracts the cytosol and cytoskeletal components from the cell and places the mixture into a tube. What result do you expect if the researcher adds a nonhydrolyzable GTP analog to the mixture in vitro?

destabilization of all polymerized microfilaments present in the tube

overstabilization of all polymerized microtubules present in the tube

destabilization of all polymerized microtubules present in the tube

overstabilization of all polymerized microfilaments present in the tube

overstabilization of all polymerized microtubules present in the tube

Which of these statements accurately describes an MTOC?

MTOCs bind and stabilize the minus ends of microtubules.

MTOCs bind and stabilize the plus ends of microtubules.

MTOCs bind and stabilize the minus ends of microfilaments.

MTOCs bind and stabilize the plus ends of microfilaments.

MTOCs bind and stabilize the minus ends of microtubules.

Which of the following is false about dynamic instability of a microtubule end?

During a catastrophe phase, hydrolysis of incorporated GTP is faster than GTP-tubulin addition, forming a GDP-cap.

Each end of a microtubule can undergo dynamic instability independently.

During rescue, GTP-tubulin assembles fast enough to reestablish a GTP cap.

During a growth phase, assembly of GTP-tubulin is faster than incorporated GTP is hydrolyzed, forming a GTP-cap.

All of the above are true.

All of the above are true.

Microtubules and microfilaments are similar with respect to each of the following except

localization similar to that of intermediate filaments in cells.

both are polymers of subunits.

association with motor proteins.

plus and minus ends for polymerization.

inherent polarity of the structure.

localization similar to that of intermediate filaments in cells.

Which of these statements is NOT true of actin?

It is a protein found in muscle.

Its polymerization is regulated by multiple proteins.

It varies considerably from organism to organism.

It gives shape to intestinal microvilli.

It varies considerably from organism to organism.

Microfilaments

are composed of two helical antiparallel strands of actin monomers.

are composed of eight protofilaments joined end to end with staggered overlaps.

are composed of α- and β-actin dimers.

polymerize at the same rate from both ends of the filament.

are composed of two helical strands of actin monomers oriented in the same direction.

are composed of two helical strands of actin monomers oriented in the same direction.

Intermediate filaments

lack the intrinsic polarity of microtubules and microfilaments, because IF tetrameric subunits are symmetric.

are grouped into five cytoplasmic classes based on the cell types in which they are found and one nuclear class.

are not found in plant cell cytoplasm.

are the most stable and least soluble cytoskeleton filaments.

All of the above are true.

All of the above are true.

Which of the following is not a function of the cytoskeleton?

establishing cell shape

passive transport

cell division

cell locomotion

organelle movement

passive transport

Actin bundles give shape and support to ________ found in intestinal mucosal cells.

microvilli

nuclei

lamellipodia

flagella

cilia

microvilli

Which is the correct order of assembly of intermediate filaments?

monomer, tetramer, protofilament, intermediate filament

protofilament, dimer, tetramer, intermediate filament

dimer, tetramer, protofilament, intermediate filament

tetramer, dimer, protofilament, intermediate filament

dimer, tetramer, protofilament, intermediate filament

Which of the following would you expect to observe in an in vitro experimental mixture containing microtubules anchored by their minus ends to centrosomes, polystyrene beads with kinesin or dynein motors attached, and ATP?

movement of beads in either direction along a single microtubule

movement of kinesin-attached beads along microtubules away from centrosomes

movement of dynein-attached beads along microtubules toward from centrosomes

removal of ATP stopping all bead movement along microtubules

All would be expected.

All would be expected.

Which of the following accurately describes the nucleotide dependence of cilia and flagella structure and function?

The structures of cilia and flagella are dependent on ATP, whereas the functions of cilia and flagella are dependent on GTP.

The structure and function of cilia and flagella are dependent on ATP.

The structures of cilia and flagella are dependent on GTP, whereas the functions of cilia and flagella are dependent on ATP.

The structure and function of cilia are dependent on ATP, whereas the structure and function of flagella are dependent on GTP.

The structures of cilia and flagella are dependent on GTP, whereas the functions of cilia and flagella are dependent on ATP.

Which of the following statements is correct with respect to flagella and cilia?

Cilia often have a helical pattern of movement.

The flagellum is usually at the leading end of a swimming sperm cell.

Cilia generally are longer than flagella.

Cilia generate a force parallel to the cell surface.

There usually are fewer cilia than flagella.

Cilia generate a force parallel to the cell surface.

Which of the following accurately describes the structure of the sarcomere of myofibrils?

The sarcomere is bounded on either size by Z lines in which myosin A bands interact with actin I bands except in the H zone.

The sarcomere is bounded on either side by M lines in which myosin I bands interact with actin A bands except in the Z zone.

The sarcomere is bounded on either side by Z lines in which myosin M bands interact with actin I bands except in the Z zone.

The sarcomere is bounded on either side by I lines in which myosin Z bands interact with actin A bands except in the H zone.

The sarcomere is bounded on either size by Z lines in which myosin A bands interact with actin I bands except in the H zone.

Which of the following changes take place as the muscle contracts?

The Z lines get closer together.

The H zones get smaller.

The I band gets smaller.

The A band gets smaller.

The Z lines get closer together, the H zones, and the I band gets smaller.

The Z lines get closer together, the H zones, and the I band gets smaller.

Which of the following sequences is in the correct order for the cyclic process by which a myosin head generates force on an actin filament for muscle contraction?

crossbridge formation, cocking of myosin head, power stroke, crossbridge dissociation

power stroke, crossbridge formation, crossbridge dissociation, cocking of myosin head

crossbridge formation, power stroke, crossbridge dissociation, power stroke, cocking of myosin head

crossbridge formation, crossbridge dissociation, cocking of myosin head, power stroke

crossbridge formation, power stroke, crossbridge dissociation, cocking of myosin head

crossbridge formation, power stroke, crossbridge dissociation, cocking of myosin head

All of the following are actin-dependent nonmuscle motilities except

cyclosis or cytoplasmic streaming.

amoeboid movement.

cleavage furrow constriction in cytokinesis.

chemotaxis.

extension of the ER.

extension of the ER.

Kinesin 1 and myosin II share each of the following features except

dimers formed by heavy chain tails coiled around each other.

plus end directed motor activity.

formation of bipolar filaments.

two heads.

ATPase activity.

formation of bipolar filaments.

Flow of vesicles from the ER to the Golgi involves all of these structures EXCEPT __________.

kinesin

dynein

dynactin

microtubules

kinesin

Which of the following proteins attaches a crawling cell to the substrate in a focal adhesion?

α-actinin

integrin

myosins

actin

titin

integrin

What do all motor proteins have in common?

A. They can be used for muscle contraction.

B. They can bind to intracellular vesicles.

C. They convert chemical energy into motion.

D. They convert actin networks into actin bundles, or axonemal microfilaments into cytoplasmic microtubules.

C. They convert chemical energy into motion.

Which of the following steps are out of order in the muscle contraction cycle?

1. ATP binds to myosin.

2. Myosin releases Pi and binds to thin filament.

3. ATP hydrolysis alters shape of myosin.

4. Myosin power stroke is accompanied by release of ADP.

5. Myosin is released from thin filaments.

A. Steps 1 & 2

B. Steps 2 & 3

C. Steps 3 & 4

D. Steps 4 & 5

B. Steps 2 & 3

How does calcium regulate muscle contraction?

A. It causes a conformational change in myosin.

B. It causes a conformational change in microfilaments.

C. It causes a conformational change in tropomyosin.

D. It enhances the rate of ATP hydrolysis by myosin.

C. It causes a conformational change in tropomyosin.

How are cilia and flagella similar to one another?

A. They generate a force parallel to the cell surface.

B. They have dynein arms essential for their function.

C. They are used in mammalian hearing.

D. They convert a cell's membrane potential into motion.

B. They have dynein arms essential for their function.

If you observed organelles moving along microtubules in different directions at the same time, you would know that the cell observed contained both _____.

A. Dynein and myosin

B. Myosin and actin

C. Kinesin and actin

D. Kinesin and dynein

D. Kinesin and dynein