Cell Bio Chapter 12 Quiz
When an action potential reaches a nerve terminal, what type of voltage-gated channels are opened and result in the fusion of synaptic vesicles with the cell membrane? a) Na+ b) Ca2+ c) K+ d) Cl-
Ca2+
Which molecule is more likely to diffuse through the lipid bilayer? a) Cl- b) ethanol
ethanol
An electrical signal crosses the synaptic cleft between the presynaptic and postsynaptic cells. a) true b) false
false
When a neuron opens voltage-gated Na+ channels, what happens to the membrane? a) it polarizes b) it depoalrizes c) no change in the membrane potential occurs
it depolarizes
The acetylcholine receptor in skeletal muscle cells is a(n) _______ ion channel. a) ligand gated b) stress gated c) voltage gated
ligand dated
Which of the following activities restores the ion gradients across the plasma membrane of an axon after an action potential has occurred? a) the opening of voltage-gated Na+ channels b) the opening of voltage-gated K+ channels c) the activity of K+ leak channels d) pumping by the Na+/K+ ATPase
pumping of the Na+/K+ ATPase
What is the name of the specialized junction between a neuron and a target cell? a) synapse b) dendrite c) nerve terminal
synapse
During an action potential, which of the following actions does not help return the membrane to its resting potential? a) the opening of voltage-gated Na+ channels b) the opening of voltage-gated K+ channels c) the inactivation of voltage-gated Na+ channels
the opening of voltage-gated Na+ channels
The communication between neurons involves the conversion between electrical and chemical signals. a) true b) false
true
Transmitter-gated ion channels are major targets for the drugs used to treat insomnia, anxiety, depression, and schizophrenia. a) true b) false
true
Which type of ion channel plays the major role in propagating electrical signals in nerve cells? a) voltage-gated b) ligand-gated c) stress-gated
voltage-gated
Which of the following is required for the secretion of neurotransmitters in response to an action potential? a) neurotransmitter receptors b) Na+-K+ pumps c) voltage-gated K+ channelsd d) voltage-gated Ca2+ channels
voltage-gated Ca2+ channels
Facilitated diffusion can be described as the favorable movement of one solute down its concentration gradient being coupled with the unfavorable movement of a second solute up its concentration gradient. a) true b) false
false
The differences in permeability between artificial lipid bilayers and cell membranes arise from variations in phospholipid content. a) true b) false
false
The ion selectivity of a channel completely depends solely on the charge of the amino acids lining the pore inside the channel. a) true b) false
false
Aquaporin channels are found in the plasma membrane, allowing the rapid passage of water molecules and small ions in and out of cells. a) true b) false
false
The net negative charge on the cytosolic side of the membrane enhances the rate of glucose import into the cell by a uniporter. a) true b) false
false
Voltage-gated K+ channels also open immediately in response to local depolarization, reducing the magnitude of the action potential. a) true b) false
false
We can test the relative permeability of a phospholipid bilayer by using a synthetic membrane that does not contain any protein components. Some uncharged, polar molecules are found to diffuse freely across these membranes, to varying degrees. Which of the following has the lowest rate of diffusion across an artificial membrane? a) glucose b) water c) glycerol d) ethanol
glucose
The Nernst equation can be used to calculate the membrane potential based on the ratio of the outer and inner ion concentration. In a resting cell, membrane potential is calculated taking only K+ ions into account. What is V when Co = 15 mM and Ci = 106 mM? a) 438.1 mV b) -52.7 mV c) 52.7 mV d) -5.3 mV
-52.7 mV
Which of the following statements describes a resting membrane potential of a neuron? a) A state in which the flow of positive and negative ions across the plasma membrane is precisely balanced b) A measure of 0 millivolts (mV) across the membrane c) A value that is chiefly a reflection of the Na+ concentration gradient across the plasma membrane
A state in which the flow of positive and negative ions across the plasma membrane is precisely balanced
Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules. In the extracellular case, what is the principal anion? a) HCO3- b) Cl- c) PO4 2- d) OH-
Cl-
Ion channels are classified as membrane transport proteins. Channels discriminate by size and charge. In addition to Na+, which one of the following ions would you expect to be able to freely diffuse through a Na+ channel? a) Mg2+ b) H+ c) K+ d) Cl-
H+
Which of the following statements is true? a) Inside the cell the quantity of positively charged ions is greater than the quantity of negatively charged ions. b) Inside the cell the quantity of positively charged ions is less than the quantity of negatively charged ions. c) Inside the cell the quantity of positively charged ions is almost exactly equal to the quantity of negatively charged ions.
Inside the cell the quantity of positively charged ions is almost exactly equal to the quantity of negatively charged ions.
If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected? a) The membrane potential is not affected by Na+. b) It becomes more negative. c) It becomes more positive. d) It is permanently reset.
It becomes more positive.
What is incorrect about a nerve impulse? a) It is another term for an action potential. b) It is electrical activity of the plasma membrane that is propagated rapidly along the membrane and sustained by automatic renewal along the way. c) It depends on the action of ligand-gated ion channels. d) It can travel at speeds of 100 meters per second.
It depends on the action of ligand-gated ion channels.
In most animal cells, which ion can move through "leak" channels in the plasma membrane and, in so doing, establishes the resting membrane potential? a) Cl- b) K+ c) Na+ d) Ca2+
K+
Which of the following has a larger electrochemical gradient across a cell's plasma membrane? a) K+ b) Na+
Na+
Lipid bilayers are highly impermeable to: a) carbon dioxide b) water c) Na+ and Cl- d) ethanol
Na+ and Cl-
Which molecule is more likely to diffuse through the lipid bilayer? a) H2O b) O2
O2
Voltage-gated channels contain charged protein domains, which are sensitive to changes in membrane potential. By responding to a threshold in the membrane potential, these voltage sensors trigger the opening of the channels. Which of the following best describes the behavior of a population of channels exposed to such a threshold? a) Some channels remain closed and some open completely. b) all channels open completely c) All channels open partly, to the same degree. d) all channels open partly, each to a different degree
Some channels remain closed and some open completely.
Which of the following statements is true? a) Amoebae have transporter proteins that actively pump water molecules from the cytoplasm to the cell exterior. b) Bacteria and animal cells rely on the Na+-K+ pump in the plasma membrane to prevent lysis resulting from osmotic imbalances. c) The Na+-K+ pump allows animal cells to thrive under conditions of very low ionic strength. d) The Na+-K+ pump helps to keep both Na+ and Cl- ions out of the cell.
The Na+-K+ pump helps to keep both Na+ and Cl- ions out of the cell.
Which of the following inhibits ions from passing through a lipid bilayer? a) The watery environment on either side of the lipid bilayer b) The hydrophilic exterior of the lipid bilayer c) The hydrophobic interior of the lipid bilayer
The hydrophobic interior of the lipid bilayer
Which of the following provides an accurate description of osmosis? a) The movement of a solute from a region of high solute concentration to low solute concentration. b) The movement of a solute from a region of low solute concentration to high solute concentration. c) The movement of water from a region of high solute concentration to low solute concentration. d) The movement of water from a region of low solute concentration to high solute concentration.
The movement of water from a region of low solute concentration to high solute concentration.
When using the Nernst equation to calculate membrane potential, we are making several assumptions about conditions in the cell. Which of the following is not a good assumption? a) The temperature is 37°C. b) The plasma membrane is primarily permeable to Na+. c) At rest, the interior of the cell is more negatively charged than the exterior. d) K+ is the principal positive ion in the cell.
The plasma membrane is primarily permeable to Na+.
Which of the following membrane transport proteins forms tiny hydrophilic pores in the membrane through which solutes can pass by diffusion? a) a transporter b) a channel c) a pump
a channel
In general, which of the following will diffuse across a lipid bilayer most rapidly? a) A small hydrophilic molecule b) a small hydrophobic molecule c) a large hydrophilic molecule d) a large hydrophobic molecule
a small hydrophobic molecule
Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called _____________. a) active transport b) free diffusion c) facilitated diffusion d) passive transport
active transport
Which molecule is more likely to diffuse through the lipid bilayer? a) amino acids b) benzene
benzene
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. The action potential is a wave of ___A___ that spreads rapidly along the neuronal plasma membrane. This wave is triggered by a local change in the membrane potential to a value that is ___B___ negative than the resting membrane potential. The action potential is propagated by the opening of ___C___-gated channels. During an action potential, the membrane potential changes from ___D___ to___E___. The action potential travels along the neuron's ___F___ to the nerve terminals. Neurons chiefly receive signals at their highly branched ___G___. what is g
dendrites
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. For an uncharged molecule, the direction of passive transport across a membrane is determined solely by its ___A___ gradient. On the other hand, for a charged molecule, the ___B___ must also be considered. The net driving force for a charged molecule across a membrane therefore has two components and is referred to as the ___C___ gradient. Active transport allows the movement of solutes against this gradient. The transporter proteins called ___D___ transporters use the movement of one solute down its gradient to provide the energy to drive the uphill transport of a second gradient. When this transporter moves both ions in the same direction across the membrane, it is considered a(n) ___E___; if the ions move in opposite directions, the transporter is considered a(n) ___F___. what is c
electrochemical
Action potentials are usually mediated by voltage-gated Ca2+ channels. a) true b) false
false
An ion channel undergoes conformational changes with each ion it passes. a) true b) false
false
Gap junctions are large pores that connect the cytosol to the extracellular space. a) true b) false
false
Which molecule is more likely to diffuse through the lipid bilayer? a) glycerol b) RNA
glycerol
When Na+ channels are opened in an animal cell, what happens to the membrane potential? a) it stays the same b) it becomes less negative c) it becomes more negative
it becomes less negative
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. The action potential is a wave of ___A___ that spreads rapidly along the neuronal plasma membrane. This wave is triggered by a local change in the membrane potential to a value that is ___B___ negative than the resting membrane potential. The action potential is propagated by the opening of ___C___-gated channels. During an action potential, the membrane potential changes from ___D___ to___E___. The action potential travels along the neuron's ___F___ to the nerve terminals. Neurons chiefly receive signals at their highly branched ___G___. what is d
negative
Transporters, in contrast to channels, work by ________________. a) specific binding to solutes b) a gating mechanism c) filtering solutes by charge d) filtering solutes by size
specific binding to solutes
_______ ion channels are found in the hair cells of the mammalian cochlea. a) ligand gated b) stress gated c) voltage gated
stress gated
Auditory hair cells in the ear depend on what type of ion channel to detect sound vibrations? a) voltage-gated b) ligand-gated c) stress-gated
stress-gated
The stimulation of auditory nerves depends on the opening and closing of channels in the auditory hair cells. Which type of gating mechanism do these cells use? a) voltage-gated b) extracellular ligand-gated c) intracellular ligand-gated d) stress-gated
stress-gated
Studies on the squid giant axon were instrumental in our current understanding of how action potentials are generated. You decide to do an experiment on the squid giant axon yourself. You add NaCl to the extracellular fluid and effectively double the amount of extracellular Na+ cation. How does this affect the action potential? a) the action potential will be smaller b) the action potential will be larger
the action potential will be larger
Which of the following mechanisms prevents osmotic swelling in plant cells? a) the collection of water in contractile vacuoles b) tough cell walls c) the activity of Na+-K+ pumps
tough cell walls
Neurotransmitters are small molecules released into the synaptic cleft after the fusion of synaptic vesicles with the presynaptic membrane. a) true b) false
true
The electrochemical gradient for K+ across the plasma membrane is small. Therefore, any movement of K+ from the inside to the outside of the cell is driven solely by its concentration gradient. a) true b) false
true
Transporters undergo transitions between different conformations, depending on whether the substrate-binding pocket is empty or occupied. a) true b) false
true
Voltage-gated Na+ channels become automatically inactivated shortly after opening, which ensures that the action potential cannot move backward along the axon. a) true b) false
true
_______ ion channels respond to changes in membrane potential. a) ligand gated b) stress gated c) voltage gated
voltage gated
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. A molecule moves down its concentration gradient by ___A___ transport, but requires ___B___ transport to move up its concentration gradient. Transporter proteins and ion channels function in membrane transport by providing a ___C___ pathway through the membrane for specific polar solutes or inorganic ions. ___D___ are highly selective in the solutes they transport, binding the solute at a specific site and changing its conformation so as to transport the solute across the membrane. On the other hand, ___E___ discriminate between solutes mainly on the basis of size and electrical charge. what is A
passive
When a neuron is stimulated by a signal, the response is at first spread locally along the membrane by what means? a) passive spread b) active transport c) action potential
passive spread
Solute movement through channels occurs by which means? a) passive transport b) active transport c) either passive or active transport
passive transport
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. The action potential is a wave of ___A___ that spreads rapidly along the neuronal plasma membrane. This wave is triggered by a local change in the membrane potential to a value that is ___B___ negative than the resting membrane potential. The action potential is propagated by the opening of ___C___-gated channels. During an action potential, the membrane potential changes from ___D___ to___E___. The action potential travels along the neuron's ___F___ to the nerve terminals. Neurons chiefly receive signals at their highly branched ___G___. what is e
positive
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. Neurons communicate with each other through specialized sites called ___A___. Many neurotransmitter receptors are ligand-gated ion channels that open transiently in the ___B___ cell membrane in response to neurotransmitters released by the ___C___ cell. Ligand-gated ion channels in nerve cell membranes convert ___D___ signals into ___E___ ones. Neurotransmitter release is stimulated by the opening of voltage-gated ___F___ in the nerve terminal membrane. what is b
postsynaptic
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. Neurons communicate with each other through specialized sites called ___A___. Many neurotransmitter receptors are ligand-gated ion channels that open transiently in the ___B___ cell membrane in response to neurotransmitters released by the ___C___ cell. Ligand-gated ion channels in nerve cell membranes convert ___D___ signals into ___E___ ones. Neurotransmitter release is stimulated by the opening of voltage-gated ___F___ in the nerve terminal membrane. what is c
presynaptic
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. Neurons communicate with each other through specialized sites called ___A___. Many neurotransmitter receptors are ligand-gated ion channels that open transiently in the ___B___ cell membrane in response to neurotransmitters released by the ___C___ cell. Ligand-gated ion channels in nerve cell membranes convert ___D___ signals into ___E___ ones. Neurotransmitter release is stimulated by the opening of voltage-gated ___F___ in the nerve terminal membrane. what is f
Ca2+ channels
You have generated antibodies that recognize the extracellular domain of the Ca2+ pump. Adding these antibodies to animal cells blocks the active transport of Ca2+ from the cytosol into the extracellular environment. What do you expect to observe with respect to intracellular Ca2+? a) Ca2+ pumps in vesicles membranes keep cytosolic calcium levels low b) Ca@+ pumps in the ER membrane keep cytosolic calcium levels low c) Ca2+ pumps in the Golgi apparatus keep cytosolic calcium levels low d) Ca2+ concentrations in the cytosol increase at a steady rate
Ca2+ pumps in the ER membrane keep cystosolic calcium levels low.
Which of the following statements is true about the concentration of calcium ions in cells? a) Calcium levels are kept high in the cytosol compared to outside the cell. b) Calcium levels are kept low in the cytosol compared to outside the cell. c) Calcium levels are kept the same in the cytosol compared to outside the cell.
Calcium levels are kept low in the cytosol compared to outside the cell.
When an individual ion channel is stimulated to open (for example, by the binding of a neurotransmitter), what is the typical activity of the ion channel? a) It opens and stays open until the neurotransmitter detaches. b) It opens and then very quickly closes, triggering the neurotransmitter to detach. c) It flickers between open and closed states, but spends more time open while the neurotransmitter is bound.
It flickers between open and closed states, but spends more time open while the neurotransmitter is bound.
Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients. Which of the following is not one of the common ways to perform active transport? a) Na+ - coupled b) K+ - coupled c) ATP-driven d) light-driven
K+ - coupled
The Na+-K+ pump in the plasma membrane of animal cells uses the energy from ATP hydrolysis to pump sodium and potassium ions against their electrochemical gradients. In which direction are the ions pumped across the membrane? a) Na+ and out K+ in b) K+ in and Na+ out c) Na+ and K+ both out d) Na+ and K+ both in
K+ in and Na+ out
Which of the following statements is true? a) Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside. b) K+ is the most plentiful positively charged ion outside the cell, while Na+ is the most plentiful inside. c) K+ and Na+ are carefully balance on each side of the cell.
Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside.
K+ leak channels are found in the plasma membrane. These channels open and close in an unregulated, random fashion. What do they accomplish in a resting cell? a) They set the K+ concentration gradient to zero. b) They set the membrane potential to zero. c) They disrupt the resting membrane potential. d) They keep the electrochemical gradient for K+ at zero.
They keep the electrochemical gradient for K+ at zero.
Which of the following statements is NOT true regarding active transport? a) some solutes are moved against their concentration gradients, from one side of a membrane to the other, using energy from ATP hydrolysis b) light-driven pumps couple the movement of solutes against their concentration gradient to an energy input from light c) a coupled transporter brings to different types of solutes across the membrane, both moving from higher concentration to lower concentration
a coupled transporter brings to different types of solutes across the membrane, both moving from higher concentration to lower concentration
The stimulation of a motor neuron ultimately results in the release of a neurotransmitter at the synapse between the neuron and a muscle cell. What type of neurotransmitter is used at these neuromuscular junctions? a) acetylcholine b) glutamate c) GABA d) glycine
acetylcholine
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. A molecule moves down its concentration gradient by ___A___ transport, but requires ___B___ transport to move up its concentration gradient. Transporter proteins and ion channels function in membrane transport by providing a ___C___ pathway through the membrane for specific polar solutes or inorganic ions. ___D___ are highly selective in the solutes they transport, binding the solute at a specific site and changing its conformation so as to transport the solute across the membrane. On the other hand, ___E___ discriminate between solutes mainly on the basis of size and electrical charge. what is B
active
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. For an uncharged molecule, the direction of passive transport across a membrane is determined solely by its ___A___ gradient. On the other hand, for a charged molecule, the ___B___ must also be considered. The net driving force for a charged molecule across a membrane therefore has two components and is referred to as the ___C___ gradient. Active transport allows the movement of solutes against this gradient. The transporter proteins called ___D___ transporters use the movement of one solute down its gradient to provide the energy to drive the uphill transport of a second gradient. When this transporter moves both ions in the same direction across the membrane, it is considered a(n) ___E___; if the ions move in opposite directions, the transporter is considered a(n) ___F___. what is F
antiport
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. The action potential is a wave of ___A___ that spreads rapidly along the neuronal plasma membrane. This wave is triggered by a local change in the membrane potential to a value that is ___B___ negative than the resting membrane potential. The action potential is propagated by the opening of ___C___-gated channels. During an action potential, the membrane potential changes from ___D___ to___E___. The action potential travels along the neuron's ___F___ to the nerve terminals. Neurons chiefly receive signals at their highly branched ___G___. what is f
axon
Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential? a) by closing Na+ channels b) by preventing the secretion of excitatory neurotransmitters c) by opening K+ channels d) by opening Cl- channels
by opening Cl- channels
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. Neurons communicate with each other through specialized sites called ___A___. Many neurotransmitter receptors are ligand-gated ion channels that open transiently in the ___B___ cell membrane in response to neurotransmitters released by the ___C___ cell. Ligand-gated ion channels in nerve cell membranes convert ___D___ signals into ___E___ ones. Neurotransmitter release is stimulated by the opening of voltage-gated ___F___ in the nerve terminal membrane. what is d
chemical
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. For an uncharged molecule, the direction of passive transport across a membrane is determined solely by its ___A___ gradient. On the other hand, for a charged molecule, the ___B___ must also be considered. The net driving force for a charged molecule across a membrane therefore has two components and is referred to as the ___C___ gradient. Active transport allows the movement of solutes against this gradient. The transporter proteins called ___D___ transporters use the movement of one solute down its gradient to provide the energy to drive the uphill transport of a second gradient. When this transporter moves both ions in the same direction across the membrane, it is considered a(n) ___E___; if the ions move in opposite directions, the transporter is considered a(n) ___F___. what is A
concentration
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. For an uncharged molecule, the direction of passive transport across a membrane is determined solely by its ___A___ gradient. On the other hand, for a charged molecule, the ___B___ must also be considered. The net driving force for a charged molecule across a membrane therefore has two components and is referred to as the ___C___ gradient. Active transport allows the movement of solutes against this gradient. The transporter proteins called ___D___ transporters use the movement of one solute down its gradient to provide the energy to drive the uphill transport of a second gradient. When this transporter moves both ions in the same direction across the membrane, it is considered a(n) ___E___; if the ions move in opposite directions, the transporter is considered a(n) ___F___. what is D
coupled
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. The action potential is a wave of ___A___ that spreads rapidly along the neuronal plasma membrane. This wave is triggered by a local change in the membrane potential to a value that is ___B___ negative than the resting membrane potential. The action potential is propagated by the opening of ___C___-gated channels. During an action potential, the membrane potential changes from ___D___ to___E___. The action potential travels along the neuron's ___F___ to the nerve terminals. Neurons chiefly receive signals at their highly branched ___G___. what is A
depolarization
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. Neurons communicate with each other through specialized sites called ___A___. Many neurotransmitter receptors are ligand-gated ion channels that open transiently in the ___B___ cell membrane in response to neurotransmitters released by the ___C___ cell. Ligand-gated ion channels in nerve cell membranes convert ___D___ signals into ___E___ ones. Neurotransmitter release is stimulated by the opening of voltage-gated ___F___ in the nerve terminal membrane. what is e
electrical
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. A molecule moves down its concentration gradient by ___A___ transport, but requires ___B___ transport to move up its concentration gradient. Transporter proteins and ion channels function in membrane transport by providing a ___C___ pathway through the membrane for specific polar solutes or inorganic ions. ___D___ are highly selective in the solutes they transport, binding the solute at a specific site and changing its conformation so as to transport the solute across the membrane. On the other hand, ___E___ discriminate between solutes mainly on the basis of size and electrical charge. what is C
hydrophilic
A hungry yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process: C6H12O6 + 2ADP + 2Pi + H+ → 2CO2 + 2CH3CH2OH + 2ATP + 2H2O Unfortunately, the grape juice is contaminated with proteases that attack some of the transport proteins in the yeast cell membrane, and the yeast cell dies. Which of the following could account for the yeast cell's demise? a) toxic buildup of carbon dioxide inside the cell b) toxic buildup of ethanol inside the cell c) diffusion of ATP out of the cell d) inability to import sugar into the cell
inability to import sugar into the cell
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. A molecule moves down its concentration gradient by ___A___ transport, but requires ___B___ transport to move up its concentration gradient. Transporter proteins and ion channels function in membrane transport by providing a ___C___ pathway through the membrane for specific polar solutes or inorganic ions. ___D___ are highly selective in the solutes they transport, binding the solute at a specific site and changing its conformation so as to transport the solute across the membrane. On the other hand, ___E___ discriminate between solutes mainly on the basis of size and electrical charge. what is E
ion channels
For voltage-gated channels, a change in the membrane potential has what effect on the channel? a) it changes the width of the channel opening b) it alters the probability that the channel will be found in its open conformation c) it either opens the channel or closes it, depending on the voltage
it alters the probability that the channel will be found in its open conformation
Which of the following best describes the behavior of a gated channel? a) it stays open continuously when stimualted b) it opens more frequently in response to a given stimulus c) it opens more widely as the stimulus becomes stronger d) it remains closed if unstimulated
it opens more frequently in response to a given stimulus
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. The action potential is a wave of ___A___ that spreads rapidly along the neuronal plasma membrane. This wave is triggered by a local change in the membrane potential to a value that is ___B___ negative than the resting membrane potential. The action potential is propagated by the opening of ___C___-gated channels. During an action potential, the membrane potential changes from ___D___ to___E___. The action potential travels along the neuron's ___F___ to the nerve terminals. Neurons chiefly receive signals at their highly branched ___G___. what is b
less
Many receptors for neurotransmitters are _______ ion channels. a) ligand gated b) stress gated c) voltage gated
ligand gated
One type of bacterial H+ pump, called bacteriorhodopsin, uses what energy source to drive the pumping of H+ across the cell's membrane? a) ATP b) light c) the electrochemical gradient of Na+ across the membrane
light
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. For an uncharged molecule, the direction of passive transport across a membrane is determined solely by its ___A___ gradient. On the other hand, for a charged molecule, the ___B___ must also be considered. The net driving force for a charged molecule across a membrane therefore has two components and is referred to as the ___C___ gradient. Active transport allows the movement of solutes against this gradient. The transporter proteins called ___D___ transporters use the movement of one solute down its gradient to provide the energy to drive the uphill transport of a second gradient. When this transporter moves both ions in the same direction across the membrane, it is considered a(n) ___E___; if the ions move in opposite directions, the transporter is considered a(n) ___F___. what is b
membrane potential
Studies on the squid giant axon were instrumental in our current understanding of how action potentials are generated. You decide to do an experiment on the squid giant axon yourself. You remove the cytoplasm in an axon and replace it with an artificial cytoplasm that contains twice the normal concentration of K+ by adding KOAc, where OAc- is an anion that is impermeable to the membrane. In this way you double the internal concentration of K+ while maintaining the bulk electrical balance of the cytoplasmic solution. Will this make the resting potential of the membrane more or less negative? a) more negative b) less negative
more negative
Which of the following would be deterred from entering an ion channel with negatively charged lining? a) positively charged ions b) negatively charged ions
negatively charged ions
Ca2+ pumps in the plasma membrane and endoplasmic reticulum are important for _____________. a) maintaining osmotic balance b) preventing Ca2+ from altering the activity of molecules in the cytosol c) providing enzymes in the endoplasmic reticulum with Ca2+ ions that are necessary for their catalytic activity d) maintaining a negative membrane potential
preventing Ca2+ from altering the activity of molecules in the cytosol
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. For an uncharged molecule, the direction of passive transport across a membrane is determined solely by its ___A___ gradient. On the other hand, for a charged molecule, the ___B___ must also be considered. The net driving force for a charged molecule across a membrane therefore has two components and is referred to as the ___C___ gradient. Active transport allows the movement of solutes against this gradient. The transporter proteins called ___D___ transporters use the movement of one solute down its gradient to provide the energy to drive the uphill transport of a second gradient. When this transporter moves both ions in the same direction across the membrane, it is considered a(n) ___E___; if the ions move in opposite directions, the transporter is considered a(n) ___F___. what is E
symport
Which term describes a coupled transporter that moves both solutes in the same direction across a membrane? a) antiport b) symport c) uniport
symport
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. Neurons communicate with each other through specialized sites called ___A___. Many neurotransmitter receptors are ligand-gated ion channels that open transiently in the ___B___ cell membrane in response to neurotransmitters released by the ___C___ cell. Ligand-gated ion channels in nerve cell membranes convert ___D___ signals into ___E___ ones. Neurotransmitter release is stimulated by the opening of voltage-gated ___F___ in the nerve terminal membrane. what is a
synapses
Studies on the squid giant axon were instrumental in our current understanding of how action potentials are generated. You decide to do an experiment on the squid giant axon yourself. You replace half of the NaCl in the extracellular fluid with choline chloride. (Choline is a monovalent cation much larger than Na+. Note that the presence of choline will not impede the flow of Na+ through its channels.) How will this affect the action potential? a) the action potential will be smaller b) the action potential will be larger
the action potential will be smaller
Which organelle is important for controlling the concentration of calcium ions in the cytosol? a) the Golgi apparatus b) the nucleus c) lysosomes d) the endoplasmic reticulum
the endoplasmic reticulum
The Na+-K+ ATPase is also known as the Na+-K+ pump. It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens immediately after the pump hydrolyzes ATP? a) Na+ is bound b) ADP is bound c) the pump is phosphorylated d) the pump changes conformation
the pump is phosphorylated
What is typically true of ion channels? a) they are open all the time b) they are gated c) they operate by active transport
they are gated
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. A molecule moves down its concentration gradient by ___A___ transport, but requires ___B___ transport to move up its concentration gradient. Transporter proteins and ion channels function in membrane transport by providing a ___C___ pathway through the membrane for specific polar solutes or inorganic ions. ___D___ are highly selective in the solutes they transport, binding the solute at a specific site and changing its conformation so as to transport the solute across the membrane. On the other hand, ___E___ discriminate between solutes mainly on the basis of size and electrical charge. What is D?
transporter
CO2 and O2 are water-soluble molecules that diffuse freely across cell membranes. a) true b) false
true
Cells expend energy in the form of ATP hydrolysis so as to maintain ion concentrations that differ from those found outside the cell. a) true b) false
true
Given enough time, virtually any molecule will diffuse across a lipid bilayer. a) true b) false
true
Most ion channels are gated, which allow them to open and close in response to a specific stimulus rather than allowing the constant, unregulated flow of ions. a) true b) false
true
For each missing section of the paragraph, select the best word or phrase from the pull-down menus below. The action potential is a wave of ___A___ that spreads rapidly along the neuronal plasma membrane. This wave is triggered by a local change in the membrane potential to a value that is ___B___ negative than the resting membrane potential. The action potential is propagated by the opening of ___C___-gated channels. During an action potential, the membrane potential changes from ___D___ to___E___. The action potential travels along the neuron's ___F___ to the nerve terminals. Neurons chiefly receive signals at their highly branched ___G___. what is c
voltage
