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1 | | Which of the following statements regarding mediated transport across cell membranes is correct? |
| | A) | All mediated transport requires the expenditure of metabolic energy. |
| | B) | All solutes crossing cell membranes by mediated transport are moved against their concentration gradient (i.e. from low concentration to high concentration). |
| | C) | All mediated transport is saturable. |
| | D) | A and B. |
| | E) | A, B and C. |
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2 | | Which of the following descriptions of movement of molecules across the plasma membrane is correct? |
| | A) | If two similar molecules can both combine with the same carrier, the presence of one of these molecules decreases the rate of entry of the other. |
| | B) | In diffusion, the rate of movement of a molecule into the cell is directly proportional to the molecule's extracellular concentration. |
| | C) | When a carrier becomes saturated, the maximum rate of transport of that carrier's solute across the membrane is reached. |
| | D) | A and B. |
| | E) | A, B and C. |
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3 | | Which of the following statements regarding the active transport of molecules across cell membranes is correct? |
| | A) | Primary active transport differs from secondary active transport in that the former uses energy derived from ATP whereas the latter does not. |
| | B) | In active transport, the affinity of a given binding site for the molecule to be transported changes as the site goes from facing one side of the membrane to facing the other side. |
| | C) | In secondary active-transport systems in which Na ions are bound to carriers, the actively transported solute always follows Na ions across the membrane. |
| | D) | In secondary active-transport systems in which Na ions are bound to carriers, the actively transported solute always moves across the membrane in the direction opposite of Na ion movement. |
| | E) | None of the above. |
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4 | | Graphs A and B below depict two ways of determining how molecules (in this case, molecules X, Y, and Z) can gain entry into a cell: (A) Increase the extracellular concentration (Co) of the molecule and measure its flux; and (B) keep Co constant and measure the intracellular concentration (Ci) of the molecule over time until equilibrium is reached. (2.0K) From the data given in the graphs, |
| | A) | molecule X probably enters the cell by active transport. |
| | B) | molecule Y probably enters the cell by facilitated diffusion. |
| | C) | molecule Z probably enters the cell by diffusion. |
| | D) | A and B. |
| | E) | B and C. |
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5 | | Regarding the sodium, potassium pump, |
| | A) | energy from ATP is directly used to move the sodium and potassium. |
| | B) | sodium can be moved either into or out of the cell. |
| | C) | more sodium ions are pumped into the cell than potassium ions are pumped out. |
| | D) | A and B. |
| | E) | A and C. |
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6 | | If the cell is placed into a solution containing 350 mOsm of non-penetrating solutes and no penetrating solutes, the cell will |
| | A) | shrink as water leaves the cell. |
| | B) | swell as water enters the cell. |
| | C) | remain the same volume as solute moves from the inside of the cell to the outside. |
| | D) | remain the same volume as solute moves from the outside of the cell to the inside. |
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7 | | A sample of human cells is placed in a beaker containing a 0.1-M solution of NaCl in 0.1M urea. A second sample of cells is placed in a beaker containing a 0.1-M solution of CaCl2 in 0.1M urea. Which of the following outcomes would you expect? |
| | A) | The cells will shrink in both solutions. |
| | B) | The cells will swell in both solutions. |
| | C) | The cells will not change volume in either solution. |
| | D) | The cells in the NaCl solution will swell and those in the CaCl2 solution will shrink. |
| | E) | The cells in the NaCl solution will swell and those in the CaCl2 solution will not change volume. |
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8 | | Which of the following solutions is isotonic to human red blood cells? |
| | A) | 150 mM sucrose. |
| | B) | 300 mM NaCl. |
| | C) | 150 mM KCl. |
| | D) | 300 mM urea. |
| | E) | None of the above. |
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9 | | Two of the solutions in questions 6-8 above are hypotonic to human red blood cells. They are |
| | A) | solutions A and B. |
| | B) | solutions A and C. |
| | C) | solutions A and D. |
| | D) | solutions B and C. |
| | E) | solutions C and D. |
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10 | | Placing human red blood cells in a hypotonic solution would cause them to |
| | A) | swell. |
| | B) | shrink. |
| | C) | first swell, then shrink. |
| | D) | first shrink, then swell. |
| | E) | stay the same size. |
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11 | | Which of the following statements regarding the movement of molecules across cell membranes is correct? |
| | A) | Exocytosis is a method by which particles may be brought into a cell. |
| | B) | Polar molecules generally diffuse more readily through the plasma membrane than do nonpolar molecules of the same size. |
| | C) | In facilitated diffusion, a molecule is moved across a membrane against its concentration gradient. |
| | D) | Water molecules are commonly actively transported out of cells. |
| | E) | None of the above is correct. |
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12 | | The active transport pump for sodium ion in intestinal epithelium |
| | A) | is located on the basolateral (blood) side of the cell. |
| | B) | is located on the luminal side of the cell. |
| | C) | secondarily provides for the active cotransport of glucose and amino acids from the intestinal lumen into the cell. |
| | D) | A and C. |
| | E) | B and C. |
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13 | | The concentration of molecule A is greater inside cells than in the extracellular fluid. This concentration difference can be accounted for by |
| | A) | diffusion of A across the cell membrane. |
| | B) | synthesis of A by the cell, whose plasma membrane is impermeable to the molecule. |
| | C) | facilitated diffusion. |
| | D) | active transport mechanisms. |
| | E) | B and D. |
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14 | | The movement of |
| | A) | glucose across cell membranes involves binding with a carrier protein in the membrane. |
| | B) | water across a cell membrane is from a region of high solute concentration to a region of low solute concentration. |
| | C) | molecules by diffusion over a distance of 25 centimeters would take only a few seconds to reach equilibrium. |
| | D) | A and B. |
| | E) | A, B and C. |
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15 | | If a cell is placed in a hypertonic solution |
| | A) | the cell will swell. |
| | B) | the concentration of water outside the cell is initially lower than the concentration inside the cell. |
| | C) | the concentration of non-penetrating solute inside the cell will decrease. |
| | D) | A and C. |
| | E) | B and C. |
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16 | | How do endocrine glands differ from exocrine glands? |
| | A) | Exocrine glands do not secrete hormones; endocrine glands do. |
| | B) | Endocrine glands do not secrete hormones; exocrine glands do. |
| | C) | Exocrine glands do not contain ducts connecting the gland to an epithelial surface; endocrine glands do. |
| | D) | A and C. |
| | E) | B and C. |
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17 | | In secondary active transport systems in which sodium ions are bound to carriers, the carrier is an ATPase. |
| | A) | True |
| | B) | False |
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