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22 Cards in this Set
- Front
- Back
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Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found? (a) anaquaporin (b) a sodium channel (c) a calcium channel (d) a proton channel |
(a) Aquaporin channels |
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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 thesemembranes, to varying degrees. Which of the following has the lowest rate of diffusion across an artificial membrane? Why? (a) glucose (b) water (c) glycerol (d) ethanol |
(a) Glucose |
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Ion channels are classified as membrane transport proteins. Channels discriminateby 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? Explain your answer. (a) Mg2+ (b) H+ (c) K+ (d) Cl– |
(b) H+ |
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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 oneof the common ways to perform active transport? (a) Na+-coupled (b) K+-coupled (c) ATP-driven (d) light-driven |
(b) K+ coupled |
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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 |
(c) the pump is phosphorylated |
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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 vesicle membranes keep cytosolic calcium levels low. (b) Ca2+ pumps in the endoplasmic reticulum 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. |
(b) Ca2+ pumps in the endoplasmic reticulum membrane keep cytosolic calcium levels low. |
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Ca2+ pumps in the plasma membrane and endoplasmic reticulum are important for_____________. (a) maintaining osmotic balance. (b) preventing Ca2+ from altering the activity ofmolecules 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. |
(b) preventing Ca2+ from altering the activity ofmolecules in the cytosol. |
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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+ channels (d) voltage-gated Ca2+ channels |
(d) Voltage-gated Ca2+ channels |
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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 |
(d) by opening Cl– channels |
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Which of the following statements about the endoplasmic reticulum (ER) is false? (a) The ER is the major site for new membrane synthesis in the cell. (b) Proteins to be delivered to the ER lumen are synthesized on smooth ER. (c) Steroid hormones are synthesized on the smooth ER. (d) The ER membrane is contiguous with the outer nuclear membrane. |
(b) Proteins to be delivered to the ER lumen are synthesized on smooth ER. |
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Which of the following statements about membrane-enclosed organelles is true? (a) In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane. (b) The nucleus is the only organelle that is surrounded by a double membrane. (c) Other than the nucleus, most organelles are small and thus, in a typical cell, only about 10% of a cell’s volume is occupied by membrane-enclosed organelles; the other 90% of the cell volume is the cytosol. (d) The nucleus is the only organelle that contains DNA. |
(a) In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane. |
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Whichof the following statements is true? (a) Lysosomes are believed to have originated from the engulfment of bacteria specialized for digestion. (b) The nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA. (c) Because bacteria do not have mitochondria, they cannot produce ATP in a membrane-dependent fashion. (d) Chloroplasts and mitochondria share their DNA. |
(b) The nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA. |
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Proteins that are fully translated in the cytosol do not end up in _______. (a) the cytosol. (b) the mitochondria. (c) the interior of the nucleus. (d) transport vesicles. |
(d) transport vesicles. |
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Proteins that are fully translated in the cytosol and lack a sorting signal will end up in ____. (a) the cytosol. (b) the mitochondria. (c) the interior of the nucleus. (d) the nuclear membrane. |
(a) the cytosol. |
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What is the role of the nuclear localization sequence in a nuclear protein? (a) It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. (b) It is a hydrophobic sequence that enables the protein to enter the nuclear membranes. (c) It aids in protein unfolding so that theprotein can thread through nuclear pores. (d) It prevents the protein from diffusing out ofthe nucleus through nuclear pores. |
(a) It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. |
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Your friend works in a biotechnology company and has discovered a drug that blocksthe ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? (a) Nuclear transport receptors would be unable tobind cargo. (b) Nuclear transport receptors would be unable to enter the nucleus. (c) Nuclear transport receptors would be unable to release their cargo in the nucleus. (d) Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils. |
(c) Nuclear transport receptors would be unable to release their cargo in the nucleus. |
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Most proteins destined to enter the endoplasmic reticulum _________. (a) are transported across the membrane after their synthesis is complete. (b) are synthesized on free ribosomes in the cytosol. (c) begin to cross the membrane while still being synthesized. (d) remain within the endoplasmic reticulum. |
(c) begin to cross the membrane while still being synthesized. |
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Your friend has just joined a lab that studies vesicle budding from the Golgi andhas been given a cell line that does not form mature vesicles. He wants to start designing some experiments but wasn’t listening carefully when he was told about the molecular defect of this cell line. He’s too embarrassed to ask and comes to you for help. He does recall that this cell line forms coated pits but vesicle budding and the removal of coat proteins don’t happen. Which of thefollowing proteins might be lacking in this cell line? (a) clathrin (b) Rab (c) dynamin (d) adaptin |
(c) dynamin |
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Step 3 in glycolysis requires the activity of phosphofructokinase to convert fructose 6-phosphate into fructose 1,6-bisphosphate. Which of the following molecules is an allosteric inhibitor of this enzyme? (a) Pi (b) AMP (c) ADP (d) ATP |
(d) ATP |
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In stage 1 of photosynthesis, a proton gradient is generated and ATP is synthesized. Where do protons become concentrated in the chloroplast? (a) thylakoidspace (b) stroma (c) inner membrane (d) thylakoidmembrane |
(a) thylakoid space |
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In stage 1 of photosynthesis, a proton gradient is generated and ATP is synthesized. Where do protons become concentrated in the chloroplast? (a) thylakoidspace (b) stroma (c) inner membrane (d) thylakoidmembrane |
(d) thylakoid membrane |
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In the final stage of the oxidation of food molecules, a gradient of protons is formed across the inner mitochondrial membrane, which is normally impermeable to protons. If cells were exposed to an agent that causes the membrane tobecome freely permeable to protons, which of the following effects would you expect to observe? (a) The ratio of ATP to ADP in the cytoplasm would fall. (b) NADH would build up. (c) Carbon dioxide production would cease. (d) The consumption of oxygen would fall. |
(a) The ratio of ATP to ADP in the cytoplasm would fall. |
