front 1 Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this fact most probably mean? | back 1 Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life. |
front 2 Which of the following statements is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal? | back 2 A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose. |
front 3 In some cells, there are many ion electrochemical gradients across the plasma membrane even though there are usually only one or two proton pumps present in the membrane. The gradients of the other ions are most likely accounted for by ________. | back 3 cotransport proteins |
front 4 The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane—more acidic outside the cell than inside the cell. In this bacterial cell, phosphate transport is an example of ________. | back 4 cotransport |
front 5 Which of the following structures would decrease the electrochemical gradient across a membrane? | back 5 a potassium channel |
front 6 Diffusion of ions across membranes through specific ion channels is driven by ________. | back 6 ion electrochemical gradients |
front 7 The voltage across a membrane is called the ________. | back 7 membrane potential |
front 8 Which of the following membrane activities requires energy from ATP hydrolysis? | back 8 movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid |
front 9 The sodium-potassium pump is called an electrogenic pump because it ________. | back 9 is used to drive the transport of glucose against a concentration gradient |
front 10 A sodium-potassium pump ________. | back 10 moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis |
front 11 When a plant cell, such as one from a tulip leaf, is submerged in a hypertonic solution, what is likely to occur? | back 11 Plasmolysis will shrink the interior of the cell. |
front 12 In which of the following environments would there be the greatest need for osmoregulation? | back 12 a salmon moving from a river into an ocean |
front 13 Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells? The animal cell is in ________. | back 13 an isotonic solution, and the plant cell is in a hypotonic solution |
front 14 What will happen to a red blood cell (RBC), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water? | back 14 The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. |
front 15 Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the fresh water ________. | back 15 is hypotonic and the salt solution is hypertonic to the cells of the celery stalks |
front 16 Five dialysis bags, constructed of a type of membrane that is
permeable to water and impermeable to sucrose, were filled with
various concentrations of sucrose and then placed in separate beakers
containing an initial concentration of 0.6 M sucrose solution. At
10-minute intervals, the bags were massed (weighed), and the percent
change in mass of each bag was graphed. | back 16 B |
front 17 Five dialysis bags, constructed of a type of membrane that is
permeable to water and impermeable to sucrose, were filled with
various concentrations of sucrose and then placed in separate beakers
containing an initial concentration of 0.6 M sucrose solution. At
10-minute intervals, the bags were massed (weighed), and the percent
change in mass of each bag was graphed. | back 17 A |
front 18 Five dialysis bags, constructed of a type of membrane that is
permeable to water and impermeable to sucrose, were filled with
various concentrations of sucrose and then placed in separate beakers
containing an initial concentration of 0.6 M sucrose solution. At
10-minute intervals, the bags were massed (weighed), and the percent
change in mass of each bag was graphed. | back 18 C |
front 19 The solutions in the arms of a U-tube are separated at the bottom of
the tube by a selectively permeable membrane. The membrane is
permeable to sodium chloride but not to glucose. Side A is filled with
a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side
B is filled with a solution containing 0.8 M glucose and 0.4 M sodium
chloride. Initially, the volume in both arms is the same. | back 19 The concentration of NaCl will increase, the concentration of glucose will decrease, and the water level will increase. |
front 20 The solutions in the arms of a U-tube are separated at the bottom of
the tube by a selectively permeable membrane. The membrane is
permeable to sodium chloride but not to glucose. Side A is filled with
a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side
B is filled with a solution containing 0.8 M glucose and 0.4 M sodium
chloride. Initially, the volume in both arms is the same. | back 20 Side A is hypotonic to side B. |
front 21 The solutions in the two arms of this U-tube are separated by a
membrane that is permeable to water and glucose but not to sucrose.
Side A is half-filled with a solution of 2 M sucrose and 1 M glucose.
Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the
liquid levels on both sides are equal. | back 21 1.5 M sucrose, 1.5 M glucose |
front 22 The solutions in the two arms of this U-tube are separated by a
membrane that is permeable to water and glucose but not to sucrose.
Side A is half-filled with a solution of 2 M sucrose and 1 M glucose.
Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the
liquid levels on both sides are equal. | back 22 The water level will be higher in side A than in side B. |
front 23 The solutions in the two arms of this U-tube are separated by a
membrane that is permeable to water and glucose but not to sucrose.
Side A is half-filled with a solution of 2 M sucrose and 1 M glucose.
Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the
liquid levels on both sides are equal. | back 23 side A is isotonic to side B |
front 24 Which of the following statements correctly describes osmosis? | back 24 In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration. |
front 25 When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane? | back 25 There is random movement of substances into and out of the cell. |
front 26 Which of the following processes includes all of the others? | back 26 passive transport |
front 27 Which of the following statements about diffusion is true? | back 27 It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. |
front 28 A research team is working on the design of a new drug for the treatment of lung cancer. To be most effective, this drug must specifically enter the cytoplasm of lung cells while not entering the cells of other tissues. Which of the following characteristics would likely enhance the specificity of this drug? | back 28 similarity of the drug molecule to other molecules normally transported lung cells |
front 29 Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes? | back 29 aquaporins |
front 30 Which of the following would likely diffuse through the lipid bilayer of a plasma membrane most rapidly? | back 30 O2 |
front 31 Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane? | back 31 It exhibits specificity for a particular type of molecule. |
front 32 Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane? | back 32 small ions |
front 33 What kinds of molecules pass through a cell membrane most easily? | back 33 small and hydrophobic |
front 34 Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures? | back 34 The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. |
front 35 In what way do the membranes of a eukaryotic cell vary? | back 35 Certain proteins are unique to each membrane. |
front 36 Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature? | back 36 The two sides of a cell membrane face different environments and carry out different functions. |
front 37 For the following questions, match the labeled component of the cell
membrane in the figure with its description. | back 37 B |
front 38 For the following questions, match the labeled component of the cell
membrane in the figure with its description. | back 38 C |
front 39 For the following questions, match the labeled component of the cell
membrane in the figure with its description. | back 39 A |
front 40 For the following questions, match the labeled component of the cell
membrane in the figure with its description. | back 40 E |
front 41 For the following questions, match the labeled component of the cell
membrane in the figure with its description. | back 41 D |
front 42 Why are lipids and proteins free to move laterally in membranes? | back 42 There are only weak hydrophobic interactions in the interior of the membrane. |
front 43 Which of the following types of molecules lack hydrophilic domains? | back 43 cholesterol |
front 44 Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer? | back 44 peripheral membrane proteins |
front 45 An animal cell lacking carbohydrates on the external surface of its plasma membrane would likely be impaired in which function? | back 45 cell-cell recognition |
front 46 According to the fluid mosaic model, a membrane ________. | back 46 is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins |
front 47 The membranes of winter wheat are able to remain fluid when it is extremely cold by ________. | back 47 increasing the proportion of unsaturated phospholipids in the membrane |
front 48 According to the fluid mosaic model of cell membranes, phospholipids ________. | back 48 can move laterally along the plane of the membrane |
front 49 A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose? | back 49 Permeability to glucose will increase. |
front 50 For a protein to be an integral membrane protein, it would have to be ________. | back 50 amphipathic, with at least one hydrophobic region |