MSCI 660 Quiz 2 Membrane Transport and Cells

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Why do cells not have membrane transport proteins for O 2 ? a. Because they need to keep the oxygen concentration low inside the reducing environment of the cell b. Because oxygen can dissolve in water and leak in via water channels c. Because oxygen can dissolve in the lipid bilayer and diffuse in and out rapidly without the need for a transporter d. Because oxygen is transported in and out of the cell in special oxygen-carrying proteins such as hemoglobin e. Because oxygen transport across a membrane is energetically unfavorable Question Type Multiple Choice Difficulty Easy Reference 11.1 Bloom's Taxonomy Understanding ID Number 10556 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.101 Protein-Free Lipid Bilayers Are Impermeable to Ions
For which of the following ions is the intracellular concentration typically higher than the extracellular concentration? a. Sodium b. Calcium c. Magnesium d. Potassium e. Chloride Question Type Multiple Choice Difficulty Easy Reference 11.1 Bloom's Taxonomy Remembering ID Number 10557 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.101 Protein-Free Lipid Bilayers Are Impermeable to Ions Imagine a small synthetic vesicle made from pure phospholipids enclosing an interior lumen containing 1 mM glucose and 1 mM sodium chloride. If the vesicle is placed in pure water, which of the following happens faster?
a. Na +  diffuses out. b. Cl –  diffuses out. c. H 2 O diffuses in. d. Glucose diffuses out. e. Sodium chloride diffuses out. Question Type Multiple Choice Difficulty Moderate Reference 11.1 Bloom's Taxonomy Understanding ID Number 10558 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.101 Protein-Free Lipid Bilayers Are Impermeable to Ions After release into the synaptic cleft, the neurotransmitter dopamine is actively taken up by the cells via specific dopamine transporters. The drug cocaine interferes with this process and is therefore called a reuptake inhibitor. The inhibition of the transporter at a certain cocaine concentration is qualitatively represented in the following graph. In transport kinetics,  V max  describes the maximal rate of transport. Based on this graph, which of the following describes the effect of cocaine on the kinetics of dopamine reuptake by the transporter?
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a. In the presence of cocaine,  V max  is unaffected, but the apparent affinity of the transporter for dopamine is reduced. b. In the presence of cocaine,  V max  is reduced, but the apparent affinity of the transporter for dopamine is unaffected. c. In the presence of cocaine,  V max  is enhanced, but the apparent affinity of the transporter for dopamine is unaffected. d. In the presence of cocaine, both  V max  and the apparent affinity of the transporter for dopamine are enhanced. e. In the presence of cocaine, both  V max  and the apparent affinity of the transporter for dopamine are unaffected, but the transporter is nevertheless inhibited. Question Type Multiple Choice Difficulty Difficult Reference 11.1
Bloom's Taxonomy Analyzing ID Number 10559 Tags Visual Revised Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.101 Protein-Free Lipid Bilayers Are Impermeable to Ions If the concentration of both solutes (shown as small  circles  and  squares ) is higher outside of the cell, which of the following transporters mediates primary active transport when actively transporting both solutes in the directions indicated? a. Transporter A b. Transporter B c. Transporter C d. Transporter D e. Transporter E
Question Type Multiple Choice Difficulty Moderate Reference 11.1 Bloom's Taxonomy Applying ID Number 10560 Tags Visual Revised Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.101 Protein-Free Lipid Bilayers Are Impermeable to Ions In contrast to transporters, the channel proteins in cellular membranes do what? a. Interact strongly with the solute(s) that they transport b. Undergo a conformational change every time they transport a solute c. Can only mediate passive transport d. Form pores that are always open Question Type Multiple Choice Difficulty Easy Reference
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11.1 Bloom's Taxonomy Understanding ID Number 10561 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.102 There Are Two Main Classes of Membrane Transport Proteins: Transporters and Channel The concentration of the dipeptide leucyl-leucine (Leu-Leu) is higher intracellularly compared to the cell’s environment. The protein Ptr2p facilitates the uptake of this peptide. What type of transport does Ptr2p engage in? a. Channel-mediated passive transport b. Transporter-mediated passive transport c. Active transport, affected by the electrochemical gradient of the dipeptide d. Active transport, with no dipeptide electrochemical gradient effect e. Simple diffusion Question Type Multiple Choice Difficulty Difficult Reference 11.1 Bloom's Taxonomy
Analyzing ID Number 10562 Tags New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.103 Active Transport Is Mediated by Transporters Coupled to an Energy Source The lactose permease in  Escherichia coli  is a H + -lactose symporter that mediates the inward active transport of lactose if this sugar is present in the environment. Which of the following is true about this transporter? a. It has a twofold pseudosymmetrical structure. b. Lactose and H +  bind to two different conformations of the transporter. c. The transporter goes through an intermediate state in which the bound lactose is open to both sides of the membrane. d. If lactose and H +  concentrations are changed sufficiently, the transporter can act as an H + -lactose antiporter. Question Type Multiple Choice Difficulty Moderate Reference 11.2 Bloom's Taxonomy Applying ID Number 10563 Tags Pickup
Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.201 Active Transport Can Be Driven by Ion-Concentration Gradients What is an accurate description of an ion channel? a. An ion channel always mediates active transport. b. An ion channeltransports a variety of ions. c. An ion channelis typically several orders of magnitude faster than a transporter. d. An ion channelis infrequently gated. e. An ion channelusually requires ATP hydrolysis. Question Type Multiple Choice Difficulty Easy Reference 11.2 Bloom's Taxonomy Understanding ID Number 10564 Tags Revised Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.201 Active Transport Can Be Driven by Ion-Concentration Gradients
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A hypothetical, secondary active transporter protein is found in the plasma membrane of a cell. With the gradients indicated, what will be the direction of movement of the two molecules? a. Circles and hexagons will both move into the cytoplasm. b. Circles and hexagons will both move out of the cytoplasm. c. Circles will move into the cytoplasm and hexagons will move out. d. Circles will move out of the cytoplasm and hexagons will move in. Question Type Multiple Choice Difficulty Moderate Reference 11.2 Bloom's Taxonomy Applying ID Number 10565 Tags Visual
New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.201 Active Transport Can Be Driven by Ion-Concentration Gradients The following possibilities represent potential transmembrane transport proteins. Which of the following matches the conformation commonly found in active transporters? a. b. c. d. e.
Question Type Multiple Choice Difficulty Difficult Reference 11.2 Bloom's Taxonomy Analyzing ID Number 10566 Tags Visual New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.201 Active Transport Can Be Driven by Ion-Concentration Gradients Which of the following plasma membrane active transporters would NOT directly contribute to the regulation of cytosolic pH? a. A Na + -driven Cl - –HCO 3 -  exchanger b. A Na + –H +  exchanger c. A P-type H + -ATPase d. A Na + -independent Cl - –HCO 3 -  exchanger e.
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A Na + -K +  pump Question Type Multiple Choice Difficulty Moderate Reference 11.2 Bloom's Taxonomy Understanding ID Number 10567 Tags New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.202 Transporters in the Plasma Membrane Regulate Cytosolic pH Which of the following normally functions to lower the pH of the cytosol? a. A Na + –H +  exchanger in the plasma membrane. b. A Na + -driven Cl – –HCO 3 –  exchanger in the plasma membrane. c. A Na + -independent Cl – –HCO 3 –  exchanger in the plasma membrane. d. A V-type ATPase in the lysosomal membrane. e. Both answers A and B above. Question Type Multiple Choice Difficulty
Easy Reference 11.2 Bloom's Taxonomy Remembering ID Number 10568 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.202 Transporters in the Plasma Membrane Regulate Cytosolic pH Which of the following transporters is NOT electrogenic? a. Na + –glucose symporter b. Ca 2+ -pump c. Na + -K +  pump d. Na + -independent Cl – –HCO 3 –  exchanger e. Bacteriorhodopsin Question Type Multiple Choice Difficulty Easy Reference 11.2 Bloom's Taxonomy Remembering
ID Number 10569 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.202 Transporters in the Plasma Membrane Regulate Cytosolic pH Many amino acids in our diet are absorbed via the transcellular transport pathway by the intestinal epithelial cells. This process requires ATP hydrolysis by which of the following? a. The Na + –amino acid symporters in the apical domain of the plasma membrane b. The Na + –amino acid antiporters in the apical domain of the plasma membrane c. The Na + -K +  pumps in the basal and lateral domains of the plasma membrane d. The amino acid carriers in the basal domain of the plasma membrane e. F-type ATPases in the apical domain of the plasma membrane Question Type Multiple Choice Difficulty Easy Reference 11.2 Bloom's Taxonomy Understanding ID Number 10570
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Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.203 An Asymmetric Distribution of Transporters in Epithelial Cells Underlies the Transcellular Transport of Solutes A particular family of ATPases is structurally related to the turbine-like pumps that acidify lysosomes and vesicles; however, they usually function in reverse, generating ATP from ADP and P i  using proton gradients across membranes. What is this family called? a. P-type pumps b. ABC transporters c. V-type pumps d. F-type pumps e. Permeases Question Type Multiple Choice Difficulty Easy Reference 11.2 Bloom's Taxonomy Understanding ID Number 10571 Tags
Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.204 There Are Three Classes of ATP-Driven Pumps If the phosphorylation domain and the actuator domain were covalently crosslinked in the closed position, in which part of the pumping cycle would the sarcoplasmic Ca 2+  pump become stuck? a. Open, facing the cytosol b. Open, facing the SR lumen c. Occluded, occupied by 2 Ca 2+ d. Occluded, occupied by 2 H + e. Occluded, but empty Question Type Multiple Choice Difficulty Moderate Reference 11.2 Bloom's Taxonomy Applying ID Number 10572 Tags New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes
Learning Objectives 11.205 A P-type ATPase Pumps Ca² ⁺ into the Sarcoplasmic Reticulum in Muscle Cells There is an auxiliary transport system associated with ABC transporters found in the plasma membrane of bacteria with double membranes. This auxiliary system consists of a porin embedded in the cell’s outer membrane, and a substrate-binding protein in the periplasmic space. As a solute moves from the cell exterior to the cytosol, how must its concentration change? Answers below are in the following order: cell exterior, periplasmic space, cytosol. a. Low, high, low b. High, low, high c. High, middle-range, low d. Low, middle-range, high e. Middle-range, low, high Question Type Multiple Choice Difficulty Moderate Reference 11.2 Bloom's Taxonomy Applying ID Number 10573 Tags New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes
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Learning Objectives 11.207 ABC Transporters Constitute the Largest Family of Membrane Transport Proteins Which of the following is a pump that hydrolyzes two ATP molecules per transport cycle? a. The cystic fibrosis transmembrane conductance regulator protein b. The multidrug resistance protein c. The Na + -K +  pump d. The Ca 2+ -pump e. The V-type ATPase Question Type Multiple Choice Difficulty Easy Reference 11.2 Bloom's Taxonomy Remembering ID Number 10574 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.207 ABC Transporters Constitute the Largest Family of Membrane Transport Proteins
What is the reason for why an aquaporin does not pass ions (such as Na + ) through? a. The Na +  ions are too small to pass through the pore rapidly enough. b. The Na +  ions are too large to pass through the narrow pore. c. The Na +  ions do not favorably interact with the wall of the pore and therefore cannot be dehydrated. d. Two Asn residues in the channel prevent the passage of Na +  ions. e. A Na +  ion must become fully hydrated to pass through. Question Type Multiple Choice Difficulty Easy Reference 11.3 Bloom's Taxonomy Understanding ID Number 10575 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.301 Aquaporins Are Permeable to Water But Impermeable to Ions
Aquaporin has a pair of key asparagine residues located on the wall almost halfway through its pore. These residues simultaneously bind to the oxygen atom of a passing water molecule, rendering it unavailable for hydrogen bonding. As a result, what happens? a. The channel can conduct negatively charged (but not positively charged) ions. b. The channel can conduct glycerol as well as water. c. The channel cannot conduct glycerol. d. The channel cannot conduct protons. e. The channel cannot conduct chloride ions. Question Type Multiple Choice Difficulty Moderate Reference 11.3 Bloom's Taxonomy Applying ID Number 10576 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.301 Aquaporins Are Permeable to Water But Impermeable to Ions The Nernst equilibrium potential for an ion that is 10 times more concentrated in the cytosol compared to the extracellular fluid is about −60 mV. How much would the
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potential be if the extracellular concentration decreases 100-fold with no change in the intracellular concentration? a. −6000 mV b. −6 mV c. −600 mV d. −20 mV e. −180 mV Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Analyzing ID Number 10577 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.303 The Membrane Potential in Animal Cells Depends Mainly on K ⁺ Leak Channels and the K ⁺ Gradient Across the Plasma Membrane Sanshool is a natural compound found in Sichuan pepper, and the cause for the numbing sensation that one experiences in the mouth. It is also known to inhibit a subset of potassium leak channels involved in maintaining the resting membrane
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potential in sensory neurons. How do you think sanshool affects these sensory neurons? a. It elevates the resting potential (to less negative values) and makes it easier to excite the neuron. b. It elevates the resting potential and makes it harder to excite the neuron. c. It lowers the resting potential and makes it easier to excite the neuron. d. It lowers the resting potential and makes it harder to excite the neuron. e. It causes hyperpolarization and decreases the spontaneous firing of the neuron. Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Evaluating ID Number 10578 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.304 The Resting Potential Decays Only Slowly When the Na ⁺ -K ⁺ Pump Is Stopped Which of the following is correct regarding the electrical properties of cellular membranes?
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a. Setting up (or changing) the membrane potential requires changing the concentrations of the ions in the microenvironment adjacent to both sides of the membrane. b. The resting potential in most animal cells is between 20 mV and 120 mV (positive inside). c. If the membrane is impermeable to an ion, the membrane potential approaches the equilibrium potential for that ion. d. The resting potential decays immediately following the inhibition of the Na + - K +  pump by a drug. Question Type Multiple Choice Difficulty Easy Reference 11.3 Bloom's Taxonomy Understanding ID Number 10579 Tags Revised Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.304 The Resting Potential Decays Only Slowly When the Na ⁺ -K ⁺ Pump Is Stopped A membrane potential is plotted over time in the following graph. The Nernst equilibrium potentials for four ions (A to D) that affect the membrane potential in this system are indicated in the graph. What happened in the time period indicated by a question mark?
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a. Channels conducting ion A opened b. Channels conducting ion B opened c. Channels conducting ion C opened d. Channels conducting ion D opened e. Channels conducting ions A and C opened Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Analyzing ID Number
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10580 Tags Visual Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.304 The Resting Potential Decays Only Slowly When the Na ⁺ -K ⁺ Pump Is Stopped Why does a potassium channel conduct K +  ions several orders of magnitude better than Na +  ions? a. The Na +  ion is too large to pass through the channel pore. b. The hydrated Na +  ion occupies a larger volume compared to the hydrated K +  ion, and is too large to pass through the channel pore. c. The Na +  ion is too small to interact with the channel in a way that facilitates the loss of water from the ion. d. The Na +  ion cannot bind to the high-affinity K + -binding sites in the channel pore. Question Type Multiple Choice Difficulty Moderate Reference 11.3 Bloom's Taxonomy Understanding ID Number 10581 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes
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Learning Objectives 11.305 The Three-Dimensional Structure of a Bacterial K ⁺ Channel Shows How an Ion Channel Can Work Which of the following is true of the bacterial K +  channel? a. The pore helices have a partial positive charge angled away from the pore. b. The vestibule is on the extracellular side of the pore. c. The extracellular-facing portions of the channel are positively charged. d. The cytosolic-facing portions of the channel are positively charged. e. The selectivity filter is lined with partial positive charges. Question Type Multiple Choice Difficulty Easy Reference 11.3 Bloom's Taxonomy Understanding ID Number 10582 Tags New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.305 The Three-Dimensional Structure of a Bacterial K ⁺ Channel Shows How an Ion Channel Can Work
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MscS and MscL are mechanosensitive channels that can be characterized in which of the following ways? a. They constitute the majority of channel proteins in the plasma membrane of auditory hair cells in the human cochlea. b. They open in response to membrane tension. c. They open at the same osmotic pressure, but differ in their ion selectivity. d. They are highly ion selective. Question Type Multiple Choice Difficulty Easy Reference 11.3 Bloom's Taxonomy Understanding ID Number 10583 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.306 Mechanosensitive Channels Allow Cells to Sense their Physical Environment A neuron’s repetitive firing rate is limited by an absolute refractory period, during which a new action potential cannot be generated. Which event is chiefly responsible for this limit? a. Opening of K +  leak channels
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b. Opening of voltage-gated Na +  channels c. Opening of transmitter-gated cation channels d. Inactivation of voltage-gated K +  channels e. Inactivation of voltage-gated Na +  channels Question Type Multiple Choice Difficulty Easy Reference 11.3 Bloom's Taxonomy Remembering ID Number 10584 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.308 Voltage-Gated Cation Channels Generate Action Potentials in Electrically Excitable Cells If the extracellular concentration of sodium ions is artificially decreased for a neuron, then what happens? a. Both the resting potential and the peak of the action potential rise significantly. b. The resting potential increases but the action potential peak does not.
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c. The resting potential hardly changes but the action potential peak is raised. d. The resting potential decreases but the action potential peak is raised. e. The resting potential hardly changes but the action potential peak is lowered. Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Analyzing ID Number 10585 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.308 Voltage-Gated Cation Channels Generate Action Potentials in Electrically Excitable Cells The inactivation rate of voltage-gated Na +  and K +  channels can regulate the firing frequency of neurons. Which of the following combinations results in the highest firing frequency? a. Rapid inactivation of both Na +  and K +  channels b. Rapid inactivation of Na +  channels, slow inactivation of K +  channels
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c. Slow inactivation of Na +  channels, rapid inactivation of K +  channels d. Slow inactivation of both Na +  and K +  channels Question Type Multiple Choice Difficulty Moderate Reference 11.3 Bloom's Taxonomy Applying ID Number 10586 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.308 Voltage-Gated Cation Channels Generate Action Potentials in Electrically Excitable Cells Which of the following situations that take place within a neuron results in action potentials that have extended depolarization phases? a. Inhibiting the voltage-gated Na +  channels b. Stimulating the voltage-gated K +  channels c. Compromising the inactivation mechanism in voltage-gated Na +  channels d. Compromising the inactivation mechanism in voltage-gated K +  channels
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Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Analyzing ID Number 10587 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.308 Voltage-Gated Cation Channels Generate Action Potentials in Electrically Excitable Cells Which graph better represents the change in the relative conductance of Na +  and K +  channels during an action potential in a neuronal membrane? a. b.
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c. d. e. Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Analyzing ID Number 10588 Tags Visual Pickup
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Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.308 Voltage-Gated Cation Channels Generate Action Potentials in Electrically Excitable Cells Myelination of axons in the peripheral nervous system does what? a. It is carried out by oligodendrocytes. b. It insulates the axons to assist in current leakage. c. It increases the speed of action potential propagation through heat conduction. d. It conserves energy because the active excitations are restricted to the nodes of Ranvier. Question Type Multiple Choice Difficulty Easy Reference 11.3 Bloom's Taxonomy Understanding ID Number 10589 Tags Revised Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives
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11.309 Myelination Increases the Speed and Efficiency of Action Potential Propagation in Nerve Cells In a voltage-clamp experiment on a squid giant axon, the membrane potential is clamped at +20 mV, as shown below. Within the same time frame, which of the curves, A to D, best represents qualitatively how the total membrane current changes? A positive value of the current represents an outward flow of cations. a. Curve A b. Curve B c. Curve C d.
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Curve D Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Analyzing ID Number 10590 Tags Visual Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.310 Patch-Clamp Recording Indicates That Individual Ion Channels Open in an All- or-Nothing Fashion There is a wide variety of structural and functional diversity among voltage-gated cation channels, although they are found throughout eukaryotes. Which statement is true about their evolutionary relatedness? a. All voltage-gated Na +  and K +  channels are related, but they are independent from Ca 2+  channels. b. All voltage-gated K +  and Ca 2+  channels are related, but they are independent from Na +  channels. c. All voltage-gated Na +  and Ca 2+  channels are related, but they are independent from K +  channels. d.
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All voltage-gated Na + , K + , and Ca 2+  channels are related within a kingdom, but they are not related between kingdoms. e. All voltage-gated Na + , K + , and Ca 2+  channels are related. Question Type Multiple Choice Difficulty Easy Reference 11.3 Bloom's Taxonomy Understanding ID Number 10591 Tags New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.311 Voltage-Gated Cation Channels Are Evolutionarily and Structurally Related A certain neuron in a mouse brain is firing about 300 times per second, whereas almost all of its neighboring neurons are firing at much lower rates of only a few times per second. What does this imply? a. This neuron expresses more depolarizing (Na +  and Ca 2+ ) than hyperpolarizing (K + ) channels compared to most of its neighbors. b. The mouse is experiencing an epileptic seizure. c. The refractory period of its voltage-gated Na +  channels is at least 300 ms. d. It releases excitatory neurotransmitters at its axon terminals.
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e. It is probably of a different type compared to most of its neighbors. Question Type Multiple Choice Difficulty Moderate Reference 11.3 Bloom's Taxonomy Applying ID Number 10592 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.312 Different Neuron Types Display Characteristic Stable Firing Properties In neurons, the synaptotagmin-1 protein is localized to presynaptic axon terminals. When activated, it facilitates the fusion of neurotransmitter-containing synaptic vesicles to the plasma membrane, leading to neurotransmitter release into the synaptic cleft. Which of the following would you expect to directly activate synaptotagmin-1 for this function? a. Binding to Mg 2+ b. Binding to Ca 2+ c. Binding to phosphatidylcholine d. Binding to K +
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e. Binding to the K +  leak channels Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Analyzing ID Number 10593 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.313 Transmitter-Gated Ion Channels Convert Chemical Signals into Electrical Ones at Chemical Synapses At synapsis between neurons, the signal is passed from the presynaptic cell to the postsynaptic cell. As the signal moves from one cell to the next, what type of signal exists at each of the following: Nerve terminal, synaptic cleft, target cell? a. Chemical, chemical, electrical b. Chemical, electrical, chemical c. Electrical, electrical, chemical d. Electrical, chemical, electrical
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e. Electrical, chemical, chemical Question Type Multiple Choice Difficulty Easy Reference 11.3 Bloom's Taxonomy Understanding ID Number 10594 Tags New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.313 Transmitter-Gated Ion Channels Convert Chemical Signals into Electrical Ones at Chemical Synapse What would cause prolonged signaling in a muscle cell at the neuromuscular junction? a. An acetylcholine reuptake inhibitor b. An acetylcholinesterase inhibitor c. An acetylcholine receptor antagonist d. Botulinum toxin, which prevents synaptic vesicles from fusing e.
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The downregulation of the acetylcholine receptor Question Type Multiple Choice Difficulty Moderate Reference 11.3 Bloom's Taxonomy Applying ID Number 10595 Tags New Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.315 The Acetylcholine Receptors at the Neuromuscular Junction Are Excitatory Transmitter-Gated Cation Channels Dopamine is a neurotransmitter involved in the reward pathways in the brain, and its decreased activity has been associated with diseases such as Parkinson’s disease and attention deficit/hyperactivity disorder (ADHD). Which of the following drugs is NOT a likely candidate to treat these diseases? a. Methylphenidate, a dopamine reuptake inhibitor b. Amphetamine, a dopamine-releasing agent that triggers the release of dopamine into the synaptic cleft c. Carbidopa, which enhances the availability of the dopamine synthesis precursors in the brain d. Forskolin, a sensitizer of dopamine receptors e.
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Chlorpromazine, a dopamine antagonist that binds to and inhibits dopamine receptors Question Type Multiple Choice Difficulty Moderate Reference 11.3 Bloom's Taxonomy Applying ID Number 10596 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.317 Many Psychoactive Drugs Act at Synapses Which of the following better represents the process of adaptation mediated by the voltage-gated Ca 2+  channels and Ca 2+ -activated K +  channels? The vertical axis in each graph is the membrane potential in the postsynaptic neuron (in millivolts), while the horizontal axis is the time of constant stimulation (in milliseconds). a. b. c.
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d. e. Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Analyzing ID Number 10597 Tags Visual Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.320 Neuronal Computation Requires a Combination of at Least Three Kinds of K ⁺ Channels
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What is NOT common between long-term potentiation and long-term depression? a. They are both important for synaptic plasticity in normal individuals. b. They both require the activation of the glutamate-gated NMDA receptors. c. They both require a rise in the intracellular concentration of Ca 2+ . d. They both result in an enhanced postsynaptic response. e. They can both last for a long time. Question Type Multiple Choice Difficulty Easy Reference 11.3 Bloom's Taxonomy Remembering ID Number 10598 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.321 Long-Term Potentiation (LTP) in the Mammalian Hippocampus Depends on Ca² ⁺ Entry Through NMDA-Receptor Channels
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Astroglial cells in the brain can actively import the amino acid glutamate from the synaptic cleft, convert it to the amino acid glutamine, and release the glutamine into the cleft to be subsequently taken up by the presynaptic neurons. The neurons then convert it back to glutamate. Why is this function of glial cells important? a. Because it competes with and replaces the direct uptake of glutamate by the neurons and thus regulates neuronal function b. Because neurons cannot produce the amino acids glutamine and glutamate and rely on the glial cells for their supply c. Because glutamate cannot be taken up directly by the neurons d. Because glutamate is an excitatory neurotransmitter and should be cleared from the synaptic cleft rapidly after its release e. Because glutamate import through glutamate–Na +  symporters in the glial cells is required for the maintenance of Na +  concentration in the synaptic cleft Question Type Multiple Choice Difficulty Difficult Reference 11.3 Bloom's Taxonomy Analyzing ID Number 10599 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives
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11.321 Long-Term Potentiation (LTP) in the Mammalian Hippocampus Depends on Ca² ⁺ Entry Through NMDA-Receptor Channels Once expressed in a neuron in the mouse brain and subjected to a flash of light, how does channelrhodopsin affect the membrane potential? a. It causes neurotransmitter release, leading to an action potential in the postsynaptic neuron. b. It increases the membrane permeability to cations and makes the membrane potential more negative. c. It depolarizes the membrane, leading to the opening of voltage-gated Na +  channels. d. It hyperpolarizes the membrane, leading to the inactivation of voltage-gated K +  channels. e. It changes the membrane potential such that voltage-gated K +  channels but not voltage-gated Na +  channels are activated. Question Type Multiple Choice Difficulty Moderate Reference 11.3 Bloom's Taxonomy Understanding ID Number 10600 Tags Pickup Chapter
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Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.322 The Use of Channelrhodopsins Has Revolutionized the Study of Neural Circuits The aggregate current crossing a patch of plasma membrane represents the degree to which each individual channel is open at that time. a. True b. False Question Type True/False Difficulty Easy Reference 11.3 Bloom's Taxonomy Understanding ID Number 10601 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.310 Patch-Clamp Recording Indicates That Individual Ion Channels Open in an All- or-Nothing Fashion Which of the following descriptions matches an ABC transporter, a P-type pump, and a V-type pump? a. ABC transporter b. P-type pump c.
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V-type pump B 1. The pumps in this family are phosphorylated at a key Asp residue in each transport cycle. A 2. This family is the largest among membrane transport proteins and includes some channels as well as pumps. C 3. The pumps in this family are responsible for the acidification of synaptic vesicles. B 4. The sodium-potassium pump is a member of this family. A 5. The multidrug resistance protein is a member of this family. Question Type Matching Difficulty Easy Reference 11.2 Bloom's Taxonomy Understanding ID Number 10602 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.204 There Are Three Classes of ATP-Driven Pumps The membrane potential in a particular hyperpolarized cell is measured to be −70 mV. For each of the following channels in this cell, the calculated Nernst equilibrium potential for the corresponding ion is presented. Indicate whether each channel is driven to pass the ion into or out of the cell.
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a. Into the cell b. Out of the cell A 1. K +  channel; the K +  equilibrium potential is −60 mV. A 2. Na +  channel; the Na +  equilibrium potential is +70 mV. A 3. Ca 2+  channel; the Ca 2+  equilibrium potential is +130 mV. A 4. Cl −  channel; the Cl –  equilibrium potential is −90 mV. Question Type Matching Difficulty Moderate Reference 11.3 Bloom's Taxonomy Applying ID Number 10603 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.303 The Membrane Potential in Animal Cells Depends Mainly on K ⁺ Leak Channels and the K ⁺ Gradient Across the Plasma Membrane
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Indicate whether the transmitter-gated channels for calcium, chloride, potassium, and sodium at a chemical synapse usually open in response to excitatory or inhibitory neurotransmitters. a. Excitatory neurotransmitters b. Inhibitory neurotransmitters A 1. Calcium B 2. Chloride B 3. Potassium A 4. Sodium Question Type Matching Difficulty Easy Reference 11.3 Bloom's Taxonomy Understanding ID Number 10604 Tags Pickup Chapter Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.312 Different Neuron Types Display Characteristic Stable Firing Properties
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The nicotinic acetylcholine receptor is an ionotropic receptor that can be activated by nicotine, a stimulant drug found in cigarettes. Additionally, α-bungarotoxin, a neurotoxin found in the venom of some snakes, binds preferentially and tightly to the closed conformation of the receptors. Another drug, donepezil, is a potent acetylcholinesterase inhibitor used to treat patients with Alzheimer’s disease. If applied at a neuromuscular junction, indicate whether each of the compounds acetylcholine, nicotine, α- bungarotoxin, and donepezil would enhance or suppress the Ca 2+  influx in the muscle cells. a. Enhance b. Suppress A 1. Acetylcholine A 2. Nicotine B 3. α-bungarotoxin A 4. Donepezil Question Type Matching Difficulty Moderate Reference 11.3 Bloom's Taxonomy Applying ID Number 10605 Tags Pickup Chapter
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Chapter 11: Small-Molecule Transport and Electrical Properties of Membranes Learning Objectives 11.315 The Acetylcholine Receptors at the Neuromuscular Junction Are Excitatory Transmitter-Gated Cation Channels Consider a human cell such as a hepatocyte. Which of the following compartments occupies a larger volume in the cell? a. Cytosol b. Nucleus c. Endoplasmic reticulum d. Mitochondria e. Peroxisomes Question Type Multiple Choice Difficulty Easy Reference 12.1 Bloom's Taxonomy Remembering ID Number 10615 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives
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12.101 All Eukaryotic Cells have the Same Basic Set of Membrane-enclosed Organelles Consider a human liver hepatocyte. Among the following membranes, which one has the largest total area? a. Plasma membrane b. Nuclear inner membrane c. Mitochondrial outer membrane d. Rough ER membrane e. Smooth ER membrane Question Type Multiple Choice Difficulty Easy Reference 12.1 Bloom's Taxonomy Remembering ID Number 10616 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.101 All Eukaryotic Cells Have the Same Basic Set of Membrane-enclosed Organelles
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A significant fraction of total membrane area in the eukaryotic cell encloses the lumen of which cytosolic organelle? a. Ribosomes b. Nucleus c. Golgi apparatus d. Endoplasmic reticulum e. Mitochondria Question Type Multiple Choice Difficulty Easy Reference 12.1 Bloom's Taxonomy Remembering ID Number 10617 Tags Revised Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.102 Evolutionary Origins Explain the Topological Relationships of Organelles Liquid–liquid phase separation is important in the assembly of membrane-less compartments called biomolecular condensates. The formation of this intricate network is reliant on what kind of molecular forces?
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a. Gravitational b. Covalent bonds c. Monovalent interactions d. Glycosylation e. Hydrogen bonds Question Type Multiple Choice Difficulty Moderate Reference 12.1 Bloom's Taxonomy Applying ID Number 10618 Tags New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.104 Multivalent Interactions Mediate Formation of Biomolecular Condensates Cyclin B1, a key cell-cycle regulatory protein in vertebrates, is mostly cytosolic before mitosis. Early in mitosis, however, the protein is phosphorylated by certain protein kinases and consequently accumulates in the nucleus. How can phosphorylation bring about nuclear accumulation of this protein? a.
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Phosphorylation within the nuclear localization signal inhibits the function of the signal. b. Phosphorylation within the nuclear export signal enhances the function of the signal. c. Phosphorylation within the nuclear export signal interferes with the function of the signal. d. Phosphorylation elsewhere on the protein enhances binding to cytosolic proteins. Question Type Multiple Choice Difficulty Moderate Reference 12.1 Bloom's Taxonomy Applying ID Number 10619 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.107 Proteins Can Move Between Compartments in Different Ways Imagine a protein that has been engineered to contain a nuclear localization signal, a nuclear export signal, a C-terminal peroxisomal targeting sequence, and a canonical endoplasmic reticulum (ER) signal sequence. With all of these signals, where would you expect to find the protein after its synthesis? a. Cytosol b.
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Nucleus c. Shuttling between the cytosol and the nucleus d. Peroxisomes e. Endoplasmic reticulum Question Type Multiple Choice Difficulty Moderate Reference 12.1 Bloom's Taxonomy Applying ID Number 10620 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.108 Sorting Signals and Sorting Receptors Direct Proteins to the Correct Cell Address A geneticist has devised a strategy to study protein translocation into the endoplasmic reticulum (ER) in yeast cells. She is interested in two different signal sequences that are thought to operate via slightly different translocation mechanisms. Using genetic engineering, she has fused the first signal sequence to a protein whose cytosolic expression is absolutely necessary for cell survival in the selective medium but is inactive when in the ER. In the same cell, she has also fused the second signal sequence to a toxic protein whose cytosolic expression leads to cell lysis but is harmless when in the ER. Whereas wild-type cells undergo lysis upon the expression of these fusion proteins, she has been able to identify viable mutants, each of which has a loss-of-function mutation in a gene encoding a protein involved in membrane translocation. The products of these genes are probably involved in what?
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a. The general transport of proteins into the ER, regardless of the type of signal sequence b. The transport of proteins with the first signal sequence but not the second one c. The transport of proteins with the second signal sequence but not the first one d. The transport of proteins with a novel signal sequence, i.e., neither the first signal sequence nor the second one Question Type Multiple Choice Difficulty Difficult Reference 12.1 Bloom's Taxonomy Analyzing ID Number 10621 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.108 Sorting Signals and Sorting Receptors Direct Proteins to the Correct Cell Address The production of new organelles requires the DNA that encodes the organelle specific proteins and what else? a.
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Digestive enzymes b. Preexisting protein translocators c. Organelle structure d. Modified lipids e. Secretory proteins Question Type Multiple Choice Difficulty Easy Reference 12.1 Bloom's Taxonomy Remembering ID Number 10622 Tags New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.109 Construction of Most Organelles Require Information in the Organelle Itself Proteins of the protein disulfide isomerase (PDI) family share common domains that harbor an active-site CXXC motif (C = cysteine; X = one of several residues). During the course of a redox reaction, one of the active-site cysteines in its reduced form can attack a disulfide bond in a substrate protein (that could itself be another PDI family member) to form a mixed disulfide between the enzyme and its substrate. This is then attacked by the other active-site cysteine, releasing the substrate in reduced form. The reverse of these reactions can occur instead in order to make disulfide bonds in target proteins. CXXA mutant PDI family proteins—in which one of the active-site cysteines is
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mutated to an alanine—can be trapped in the intermediate mixed disulfide state for an elongated time, facilitating the identification of their substrate proteins. Using these mutations in each of three interacting PDI family proteins—A, B, and C (one mutation at a time)—you have discovered that the mutant B interacts with A and C, while mutant A interacts with C but not with B. Finally, mutant C interacts with neither of the other two. The following diagram shows the thermodynamically favorable flow of electrons (plus protons) in the cascade involving these three proteins. Based on your results above, what proteins correspond to 1, 2, and 3 in the diagram, respectively? a. ABC b. BAC c. ACB d. BCA Question Type Multiple Choice Difficulty Difficult
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Reference 12.2 Bloom's Taxonomy Analyzing ID Number 10623 Tags Visual Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.202 Signal Sequences Were First Discovered in Proteins Imported into the Rough ER Which statement is true about the signal-recognition particle (SRP)? a. It is a heterodimeric protein. b. It transiently inhibits translation and polypeptide elongation by binding to and inhibiting the elongation factors. c. It accompanies the nascent polypeptide all the way into the ER lumen. d. It binds GTP. e. It is permanently attached to the cytosolic face of the ER membrane, thus bringing the ribosomes into close proximity of the translocon. Question Type Multiple Choice Difficulty Easy Reference
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12.2 Bloom's Taxonomy Understanding ID Number 10624 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.203 A Signal-Recognition Particle (SRP) Directs the ER Signal Sequence to a Specific Receptor at the ER You set up an  in vitro  translation system containing the entire translation machinery but devoid of any component of the endoplasmic reticulum (ER) targeting machinery. To this system, you can add mRNA encoding either a 20 kD secretory protein or a 20 kD cytosolic protein. You perform  in vitro  translation in the presence of radioactively labeled methionine, with or without the addition of saturating amounts of SRP or microsomes, as indicated below. After separating the protein products by SDS-PAGE, and visualizing the radioactivity by autoradiography, you obtain the following results. The presence or absence of each component in the reaction is indicated at the top of the corresponding lane(s) by + and –, respectively. The numbers on the left indicate the apparent molecular mass (×1000) of spots on the gel. Which protein (X or Y) is the secretory protein? Which of the reactions (1 or 2) contained SRP?
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a. X; 1 b. X; 2 c. Y; 1 d. Y; 2 Question Type Multiple Choice Difficulty
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Difficult Reference 12.2 Bloom's Taxonomy Analyzing ID Number 10625 Tags Visual Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.203 A Signal-Recognition Particle (SRP) Directs the ER Signal Sequence to a Specific Receptor at the ER The Sec61 translocator facilitates the translocation of proteins that contain a signal sequence. What organelle are these proteins destined for? a. Golgi b. Nucleus c. ER d. Chloroplast e. Lipid Question Type Multiple Choice Difficulty Easy Reference
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12.2 Bloom's Taxonomy Remembering ID Number 10626 Tags Revised Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.204 The Polypeptide Chain Passes Through a Signal Sequence-Gated Aqueous Channel in the Translocator Which of the following is NOT a likely ER signal sequence recognized by the signal- recognition particle? All sequences are written with their N-terminus on the left. a. Met-Lys-Leu-Ser-Leu-Val-Ala-Ala-Met-Leu-Leu-Leu-Leu-Ser-Ala-Ala-Arg-Ala b. Met-Glu-Met-Phe-Gln-Gly-Leu-Leu-Leu-Leu-Leu-Leu-Leu-Leu-Ser-Met-Gly-Gly- Thr-Trp-Ala c. Met-Lys-Ala-Lys-Leu-Leu-Val-Leu-Leu-Tyr-Ala-Phe-Val-Ala-Gly-Asn d. Met-Met-Ala-Ala-Gly-Pro-Arg-Thr-Ser-Leu-Leu-Leu-Ala-Phe-Ala-Leu-Leu-Cys- Leu-Pro-Trp-Thr-Gln-Val-Val e. Met-Leu-Ser-Leu-Arg-Gln-Ser-Ile-Arg-Phe-Phe-Lys-Pro-Ala-Thr-Arg-Thr- Leu-Ser-Ser-Arg-Tyr-Leu Question Type Multiple Choice Difficulty Moderate Reference
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12.2 Bloom's Taxonomy Understanding ID Number 10627 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.207 Hydrophobic Segments of Multipass Transmembrane Proteins are Interpreted Contextually to Determine Their Orientation When the hydrophobic transmembrane α helix at the C-terminus of an ER tail-anchored protein emerges from the ribosome, the tail-anchored binding domain (TABD) of the Get3 ATPase binds to it. The job of TABD in Get3 is similar to that of the flexible hydrophobic domain in the SRP54 protein of the signal-recognition particle, in that it also has to recognize a degenerate set of hydrophobic α-helices. Considering the corresponding SRP4 domain, the Get3 binding site is composed mostly of what type of residues? a. Tyrosine and tryptophan b. Serine and methionine c. Glycine and cysteine d. Methionine and glycine e. Aspartic acid and glutamate Question Type Multiple Choice Difficulty
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Moderate Reference 12.2 Bloom's Taxonomy Applying ID Number 10628 Tags Revised Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.207 Hydrophobic Segments of Multipass Transmembrane Proteins are Interpreted Contextually to Determine Their Orientation The following diagram depicts the topology of a multipass transmembrane protein in the endoplasmic reticulum (ER) membrane. Which set of helices act as stop-transfer signals in this protein? a. 1, 2, 3 b. 4, 5, 6 c. 1, 3, 5 d. 2, 4, 6
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e. 1, 6 Question Type Multiple Choice Difficulty Difficult Reference 12.2 Bloom's Taxonomy Analyzing ID Number 10629 Tags Visual Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.207 Hydrophobic Segments of Multipass Transmembrane Proteins are Interpreted Contextually to Determine Their Orientation Consider the following hydropathy plot for a multipass transmembrane protein in the plasma membrane. Are the protein termini expected to be located inside (I) or outside (O) of the cell? Which of the regions indicated as 2 and 3 in the plot is expected to have more positively charged residues? The position of positively charged residues near the first transmembrane helix is indicated by an asterisk on the plot.
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a. I; 2 b. I; 3 c. O; 2 d. O; 3 Question Type Multiple Choice Difficulty Difficult Reference 12.2 Bloom's Taxonomy Analyzing ID Number 10630 Tags Visual Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.207 Hydrophobic Segments of Multipass Transmembrane Proteins are Interpreted Contextually to Determine Their Orientation Mitochondrial hsp70 relates to matrix protein import as what relates to post-translational ER protein import? a. Ribosome b.
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Sec61 c. Sec63 d. BiP e. PDI Question Type Multiple Choice Difficulty Easy Reference 12.2 Bloom's Taxonomy Understanding ID Number 10631 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.208 Some Proteins Are Integrated into the ER Membrane by a Post-translational Mechanism A protein is covalently attached to glycosylphosphatidylinositol. Which of the following is typically NOT true regarding this protein? a. The linkage of the anchor to the C-terminus of the protein occurs in the ER. b. The attachment of the anchor coincides with cleavage of a C-terminal transmembrane segment of the protein precursor.
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c. The protein is likely to be an ER resident, helping with the folding of nascent imported proteins. d. A phospholipase can cleave the protein from the membrane. e. The anchor affects the localization of the protein in the membrane. Question Type Multiple Choice Difficulty Easy Reference 12.2 Bloom's Taxonomy Remembering ID Number 10632 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.209 Some Membrane Proteins Acquire a Covalently Attached Glycosylphosphatidylinositol (GPI) Anchor Consider a transmembrane protein with the following topology that has an internal signal sequence (helix 1). If you fuse a canonical ER signal sequence at the N-terminus of this protein, how would you expect the topology to change? The ER lumen is at the bottom in all drawings. For simplicity, assume that the effect of charged residues flanking the transmembrane helices is negligible in this case.
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a. b. c.
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d. e. Question Type Multiple Choice Difficulty Moderate Reference 12.2 Bloom's Taxonomy Applying ID Number 10633 Tags Visual Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.210 Translocated Polypeptide Chains Fold and Assemble in the Lumen of the Rough ER Calnexin, a calcium-dependent chaperone localized to the ER membrane, binds to folded proteins that contain what type of sugar modification?
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a. O -linked glycosidic linkage b. N -linked oligosaccharide c. O -linked oligosaccharide d. N -linked glycosidic linkage e. N -linked glucosidase Question Type Multiple Choice Difficulty Easy Reference 12.2 Bloom's Taxonomy Remembering ID Number 10634 Tags New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.211 Most Proteins Synthesized in the Rough ER Are Glycosylated by the Addition of a Common N-Linked Oligosaccharide Rough microsomes can be subjected to a “salt extraction” procedure in which a high salt concentration is used to remove membrane-associated ribosomes and peripheral proteins. Such salt-extracted microsomes are known to be translocation-incompetent, meaning that when present co-translationally  in vitro , they fail to protect translated proteins from protease digestion. However, adding back an 11S particle (S is the sedimentation coefficient) purified from the salt-wash fraction is sufficient to restore the
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protein-translocation activity of the salt-extracted microsomes. Which of the following do you think is true regarding the 11S particle? a. It is composed of 21 proteins. b. It is a digestion product of ER-associated ribosomes. c. It is normally assembled in the nucleus and exported to the cytoplasm by exportins. d. It is an ER integral membrane protein that can interact with the translocon. e. It requires high salt concentration for its function  in vivo . Question Type Multiple Choice Difficulty Difficult Reference 12.2 Bloom's Taxonomy Analyzing ID Number 10635 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.214 Misfolded Proteins in the ER Activate an Unfolded Protein Response Misfolded proteins in the ER may actively undergo any of the following EXCEPT what? a.
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Binding to chaperones such as BiP to allow unfolding and refolding b. Binding to chaperones such as calnexin to prevent aggregation c. Being transported back to the cytosol for degradation d. Being expelled to the Golgi apparatus for disposal e. Being glycosylated and binding to lectins Question Type Multiple Choice Difficulty Easy Reference 12.2 Bloom's Taxonomy Understanding ID Number 10636 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.214 Misfolded Proteins in the ER Activate an Unfolded Protein Response Organelle-mediated compartmentalization of the eukaryotic cell allows for the segregation and regulation of various reactions. Mechanisms have evolved to facilitate the exchange of materials, including the formation of membrane contact sites (MCS). Which of the following describes the main function of MCSs? a. Cytoskeleton networking
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b. Lipid biosynthesis c. Tethering one organelle to another organelle d. Neuron synapsis e. Apoptosis Question Type Multiple Choice Difficulty Easy Reference 12.2 Bloom's Taxonomy Understanding ID Number 10637 Tags New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.216 Membrane Contact Sites between the ER and Other Organelles Facilitate Selective Lipid Transfer Betaoxidation is the process of catabolizing fatty acids into acetyl CoA. Identify the cell organelle(s) responsible for this process in mammalian cells. a. Phospholipids and plasmalogens b.
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Mitochondria and peroxisomes c. Glyoxymes and chloroplasts d. Chloroplasts and mitochondria e. Peroxisomes and ER Question Type Multiple Choice Difficulty Easy Reference 12.3 Bloom's Taxonomy Remembering ID Number 10638 Tags New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.301 Peroxisomes Use Molecular Oxygen and Hydrogen Peroxide to Perform Oxidation Reactions Which reaction is normally catalyzed by the enzyme catalase in the peroxisome? a. 2O 2 –  + 2H +  → H 2 O 2  + O 2 b. FMNH 2  + O 2  → FMN + H 2 O 2 c. C 2 H 5 OH (ethanol) + NAD +  → C 2 H 4 O (acetaldehyde) + NADH + H +
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d. 2H 2 O 2  → 2H 2 O + O 2 e. Both C and D Question Type Multiple Choice Difficulty Easy Reference 12.3 Bloom's Taxonomy Remembering ID Number 10639 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.301 Peroxisomes Use Molecular Oxygen and Hydrogen Peroxide to Perform Oxidation Reactions Below is an illustration of a chloroplast. What is the name of the area identified by a question mark? a.
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Intermembrane space b. Inner membrane c. Thylakoid d. Stroma e. Thylakoid space Question Type Multiple Choice Difficulty Easy Reference 12.4 Bloom's Taxonomy Understanding ID Number 10640 Tags Visual New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.401 Translocation into Mitochondria Depends on Signal Sequences and Protein Translocators 12.406 Two Signal Sequences Direct Proteins to the Thylakoid Membrane in Chloroplasts Certain cysteine-containing proteins of the mitochondrial intermembrane space are imported from the cytosol with the help of the Mia40 protein via a disulfide relay system. What drives the unidirectional import of these proteins? Are these proteins reduced or oxidized at their cysteine residues upon import?
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a. ATP hydrolysis; oxidized b. The electron-transport chain; oxidized c. ATP hydrolysis; neither oxidized nor reduced d. ATP hydrolysis; reduced e. The electron-transport chain; reduced Question Type Multiple Choice Difficulty Moderate Reference 12.4 Bloom's Taxonomy Applying ID Number 10641 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.403 Protein Import is Powered by ATP Hydrolysis, a Membrane Potential, and Redox Potential Which of the following proteins or protein complexes is directly required for the targeting of mitochondrial inner membrane multipass proteins, such as metabolite transporters, whose signal sequence is normally not cleaved after import?
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a. TIM22 b. TIM23 c. OXA d. Mia40 e. SAM Question Type Multiple Choice Difficulty Easy Reference 12.4 Bloom's Taxonomy Remembering ID Number 10642 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.404 Transport Into the Inner Mitochondrial Membrane Occurs Via Several Routes The import of nuclear-encoded mitochondrial proteins requires the use of protein translocators. Proteins spanning the mitochondrial outer membrane utilize the TOM complex for proper localization. Identify the translocator below responsible for the import of inner mitochondrial membrane proteins. a. TOM
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b. Hsp70 c. TIM23 d. OXA1 e. TIM22 Question Type Multiple Choice Difficulty Easy Reference 12.4 Bloom's Taxonomy Remembering ID Number 10643 Tags New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.404 Transport Into the Inner Mitochondrial Membrane Occurs Via Several Routes Thylakoids are membrane-enclosed compartments found in the chloroplasts of photosynthetic eukaryotic cells. Translocation of proteins into the thylakoid lumen or membrane can occur by which pathway? a. Nuclear import pathway b. Endocytic pathway
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c. IRE1 pathway d. Sec pathway e. Unfolded protein response pathway Question Type Multiple Choice Difficulty Easy Reference 12.4 Bloom's Taxonomy Remembering ID Number 10644 Tags New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.406 Two Signal Sequences Direct Proteins to the Thylakoid Membrane in Chloroplasts Regarding protein import in a photosynthetic eukaryotic cell, targeting to which location requires two different signal peptides? a. Chloroplast b. Lysosome c.
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Nucleus d. Rough ER e. Golgi Apparatus Question Type Multiple Choice Difficulty Easy Reference 12.4 Bloom's Taxonomy Remembering ID Number 10645 Tags New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.406 Two Signal Sequences Direct Proteins to the Thylakoid Membrane in Chloroplasts The mitochondria evolved through an endosymbiotic relationship between a Gram- negative ancestor and an ancestral host cell. The outer membrane of mitochondria and Gram-negative bacteria both contain β-barrel proteins, evidence of this evolutionary relationship. After synthesis in the cytosol, β-barrel proteins are transported to which mitochondrial compartment first? a. Mitochondrial inner membrane b. Mitochondrial outer membrane c. Chloroplast thylakoid
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d. Mitochondrial matrix e. Mitochondrial intermembrane space Question Type Multiple Choice Difficulty Moderate Reference 12.4 Bloom's Taxonomy Applying ID Number 10646 Tags New Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.405 Bacteria and Mitochondria Use Similar Mechanisms to Insert β-Barrels into their Outer Membrane In the following schematic diagram of a nuclear pore complex, on which side is the cytosol located? What is the approximate diameter of the pore, as indicated by the vertical bar?
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a. Right; 1 µm b. Right; 0.1 µm c. Left; 1 µm d. Left; 0.1 µm Question Type Multiple Choice Difficulty Moderate Reference 12.5 Bloom's Taxonomy Applying ID Number 10647
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Tags Visual Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.501 Nuclear Pore Complexes Perforate the Nuclear Envelope Sorting signals are essential in the import of molecules in the cell. Which of the following scenarios would lead to the correct sorting of molecules to the nucleus? a. Phosphorylation causes a conformational change exposing the nuclear receptor tail. b. In a single pore, a nuclear localization signal (NLS)-containing protein is imported, while at the same time a nuclear export signal (NES)-containing protein is exported. c. A nuclear import receptor is modified in the cytosol. d. A protein containing an NLS is imported into the mitochondria. Question Type Multiple Choice Difficulty Moderate Reference 12.5 Bloom's Taxonomy Understanding ID Number 10648 Tags Revised Chapter Chapter 12: Intracellular Organization and Protein Sorting
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Learning Objectives 12.502 Nuclear Localization Signals Direct Proteins to the Nucleus Consider a transcription regulatory protein that has both a nuclear localization signal (NLS) and a nuclear export signal (NES) and is normally found both in the nucleus and in the cytosol at comparable concentrations. This protein has a high-affinity binding partner in the nucleus. Upon activation of a certain signaling pathway, the binding protein is ubiquitylated and degraded. What is the result? a. The transcription regulatory protein accumulates in the nucleus. b. The transcription regulatory protein accumulates in the cytosol. c. The distribution of the transcription regulatory protein does not change, but the expression of its target genes may be altered. d. The distribution of the transcription regulatory protein does not change, and the expression of its target genes is not necessarily changed as a result of the degradation event. Question Type Multiple Choice Difficulty Difficult Reference 12.5 Bloom's Taxonomy Evaluating ID Number 10649 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.502 Nuclear Localization Signals Direct Proteins to the Nucleus
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According to the model for nuclear transport described in this chapter, what do you think would happen if you could artificially limit all Ran-GAP activity to the nucleus and all Ran-GEF activity to the cytosol? a. Proteins containing an NLS would be actively exported from the nucleus, while NES-containing proteins would be actively imported. b. Both import and export of nuclear proteins would be stalled, as they lose their directionality. c. Protein import into the nucleus would be reversed, but export would be unaffected. d. Protein import into the nucleus would be stalled, but export would be unaffected. e. Nothing would change; this is the normal Ran-GAP and Ran-GEF distribution. Question Type Multiple Choice Difficulty Moderate Reference 12.5 Bloom's Taxonomy Applying ID Number 10650 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.504 The Ran GTPase Imposes Directionality on Nuclear Import Through NPCs
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The formation of a stable ternary complex involving Ran GTPase, a nuclear transport receptor, and a cargo protein occurs during which process(es)? a. Both nuclear import and export b. Nuclear import, but not export c. Nuclear export, but not import d. Neither nuclear import nor export Question Type Multiple Choice Difficulty Easy Reference 12.5 Bloom's Taxonomy Remembering ID Number 10651 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.504 The Ran GTPase Imposes Directionality on Nuclear Import Through NPCs Consider two cells, A and B. Both are approximately spherical, but cell A is a bacterium with a diameter of only about 1 µm, while the diameter of the eukaryotic cell B is about 10 µm. If the plasma membrane in the eukaryotic cell comprises only about 2% of the total cell membrane, then cell B has a higher ratio of total cell membrane to volume. a.
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True b. False Question Type True/False Difficulty Difficult Reference 12.1 Bloom's Taxonomy Analyzing ID Number 10652 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.102 Evolutionary Origins Explain the Topological Relationships of Organelles Almost all eukaryotic cells have plastids, but only plant cells have chloroplasts capable of photosynthesis. a. True b. False Question Type True/False Difficulty Easy Reference 12.1 Bloom's Taxonomy Remembering ID Number 10653 Tags Pickup Chapter
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Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.102 Evolutionary Origins Explain the Topological Relationships of Organelles The signal-recognition particle is not the only factor that evaluates the authenticity of endoplasmic reticulum (ER) signal sequences in proteins. The Sec61 complex is also able to recognize the signal sequences and “opens” after binding to them. Even single- point mutations within the signal sequence of a protein can render the protein unable to enter the ER efficiently, as the Sec61 complex does not readily open in response to the mutant sequence. However, “suppressor” mutations in genes encoding components of the translocation pathway, including the Sec61 subunits, can partially restore the wild- type localization of proteins with mutant signal sequences. Many such suppressor mutations (also called  prl  mutations) map to or near the “plug” domain in the Sec61 translocon. These mutations, including the deletion of the entire plug, generally result in destabilization of the closed conformation of the translocon and favor its open conformation. Your friend has mutated a certain residue in the plug domain of the yeast Sec61. She has just finished measuring the translocation efficiency of an ER protein with either a wild-type or a mutant (defective) signal sequence, either in wild-type or in her Sec61- mutant cells, and has obtained the following results. Based on these early results, the Sec61 mutation shows a  prl  phenotype.
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a. True b. False Question Type True/False Difficulty Difficult Reference 12.2 Bloom's Taxonomy Analyzing ID Number 10654 Tags Visual Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.203 A Signal-Recognition Particle (SRP) Directs the ER Signal Sequence to a Specific Receptor at the ER Most proteins synthesized in the rough ER are  N -glycosylated, and some of them require this modification for their correct folding. a. True b. False Question Type True/False Difficulty Easy Reference 12.2 Bloom's Taxonomy
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Remembering ID Number 10655 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.211 Most Proteins Synthesized in the Rough ER Are Glycosylated by the Addition of a Common N-Linked Oligosaccharide All peroxisomal proteins are encoded in the nucleus. a. True b. False Question Type True/False Difficulty Easy Reference 12.3 Bloom's Taxonomy Remembering ID Number 10656 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.302 Short Signal Sequences Direct the Import of Proteins into Peroxisomes Signal sequences that target precursor proteins to the mitochondrial matrix form an α helix in which positively charged residues cluster near its N-terminus, while uncharged or hydrophobic residues cluster near the other side. a. True
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b. False Question Type True/False Difficulty Easy Reference 12.4 Bloom's Taxonomy Understanding ID Number 10657 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.401 Translocation into Mitochondria Depends on Signal Sequences and Protein Translocators Tom40 is a nuclear-encoded essential subunit of the TOM complex in the outer mitochondrial membrane. It is a β-barrel protein that forms the pore through which precursor proteins enter the intermembrane space from the cytosol. Tom40 is translocated through the inner membrane as a precursor. a. True b. False Question Type True/False Difficulty Easy Reference 12.4 Bloom's Taxonomy Remembering ID Number 10658
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Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.405 Bacteria and Mitochondria Use Similar Mechanisms to Insert β-Barrels into their Outer Membrane Most nuclear import receptors contain unstructured domains with FG-repeats. a. True b. False Question Type True/False Difficulty Easy Reference 12.5 Bloom's Taxonomy Remembering ID Number 10659 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.503 Nuclear Import Receptors Bind to Both Nuclear Localization Signals and NPC Proteins Ribosomal proteins pass through the nuclear pore complexes twice: They are imported into the nucleus after synthesis and exported from the nucleus after assembly with ribosomal RNA. a. True
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b. False Question Type True/False Difficulty Easy Reference 12.5 Bloom's Taxonomy Understanding ID Number 10660 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.505 Nuclear Export Works Like Nuclear Import, But in Reverse Indicate whether the location of each of the following is topologically equivalent to the cytosol or the extracellular space. a. Cytosol b. Extracellular space A 1. Ribosomes A 2. Chromatin B 3. Lysosomal hydrolases B 4.
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Calcium ions in the ER B 5. Peroxisomal catalase Question Type Matching Difficulty Easy Reference 12.1 Bloom's Taxonomy Remembering ID Number 10661 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.101 All Eukaryotic Cells Have the Same Basic Set of Membrane-enclosed Organelles Indicate whether each of the following transport processes occurs via the mechanisms described as gated transport, transmembrane transport, or vesicular transport. a. Gated transport b. Transmembrane transport c. Vesicular transport A 1. Import into nucleus A 2. Export from nucleus
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B 3. Import into mitochondria C 4. Return from Golgi to ER B 5. Return from ER to cytosol Question Type Matching Difficulty Easy Reference 12.1 Bloom's Taxonomy Understanding ID Number 10662 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.107 Proteins Can Move Between Compartments in Different Ways Indicate whether each of the following descriptions better matches the rough or smooth endoplasmic reticulum (ER). a. Rough endoplasmic reticulum b. Smooth endoplasmic reticulum B 1. It mostly has a tubular appearance. B
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2. It contains the transitional ER. A 3. It is coated by ribosomes. B 4. It can be specialized for functions such as detoxification and lipid metabolism. B 5. Sarcoplasmic reticulum in muscle cells is one of its specialized forms. Question Type Matching Difficulty Easy Reference 12.2 Bloom's Taxonomy Understanding ID Number 10663 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.201 The ER Is Structurally and Functionally Diverse Indicate whether the C-terminus or the N-terminus of each of the following proteins is expected to be located in the cytosol upon membrane integration of the protein. a. C-terminus b. N-terminus B 1.
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A single-pass transmembrane protein that has one N-terminal signal sequence and one internal stop-transfer signal B 2. A single-pass transmembrane protein that has one internal signal sequence that is preceded by a patch of positively charged residues A 3. An ER tail-anchored protein Question Type Matching Difficulty Moderate Reference 12.2 Bloom's Taxonomy Applying ID Number 10664 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.205 Translocation Across the ER Membrane Does Not Always Require Ongoing Polypeptide Chain Elongation Indicate whether each of the following occurs on the cytosolic side of the ER membrane, on the luminal side of the ER membrane, or in the Golgi apparatus. a. Cytosolic side b. Luminal side c. Golgi apparatus A
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1. Assembly of GlcNAc oligosaccharides on dolichol phosphate A 2. Synthesis of phosphatidylcholine C 3. Synthesis of sphingomyelin A 4. Ubiquitylation of misfolded ER protein A 5. Synthesis of phosphatidic acid Question Type Matching Difficulty Easy Reference 12.2 Bloom's Taxonomy Remembering ID Number 10665 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.209 Some Membrane Proteins Acquire a Covalently Attached Glycosylphosphatidylinositol (GPI) Anchor Indicate whether each of the following descriptions better matches the ATF6, the IRE1, or the PERK branch of the ER unfolded protein response. a. ATF6 b. IRE1
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c. PERK B 1. It involves a noncanonical cytoplasmic splicing process. A 2. Its sensor is a latent transcription regulator. A 3. It involves regulated proteolysis of the sensor protein in the Golgi apparatus. B 4. Its sensor bears both kinase and endoribonuclease activities. Question Type Matching Difficulty Easy Reference 12.2 Bloom's Taxonomy Understanding ID Number 10666 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.213 Improperly Folded Proteins Are Exported from the ER and Degraded in the Cytosol Indicate whether each of the following descriptions refers to protein import into mitochondria, chloroplasts, or both. a. Mitochondria b.
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Chloroplasts c. Both B 1. ATP and GTP hydrolysis drive translocation into the organelle. B 2. The organelle has an extra compartment that requires extra signal sequences for protein targeting. A 3. Transport through the double membrane is driven in part by an H +  gradient across the inner membrane. C 4. Imported precursor proteins have amphiphilic N-terminal signal sequences that are usually removed after use. C 5. Hsp70 family chaperones inside the organelle assist in protein translocation during import. Question Type Matching Difficulty Easy Reference 12.4 Bloom's Taxonomy Remembering ID Number 10667 Tags Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.403 Protein Import is Powered by ATP Hydrolysis, a Membrane Potential, and Redox Potential
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In the following graph, the magnitude of concentration difference across the nuclear pore complexes (NPCs) is plotted for four molecules (A to D) as a function of time, starting from an arbitrarily chosen initial concentration difference. Indicate which curve corresponds to each of the following molecules. a. Curve A b. Curve B c. Curve C d. Curve D B
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1. A large protein that is being actively transported across the NPC D 2. A small water-soluble molecule C 3. A small protein composed of a few dozen residues A 4. A large protein that is NOT actively transported into or out of the nucleus Question Type Matching Difficulty Difficult Reference 12.5 Bloom's Taxonomy Analyzing ID Number 10668 Tags Visual Pickup Chapter Chapter 12: Intracellular Organization and Protein Sorting Learning Objectives 12.506 Transport Through NPCs Can Be Regulated by Controlling Access to the Transport Machinery
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