Becker's World of the Cell, 8e (Hardin/Bertoni/Kleinsmith) Chapter 8 Transport Across Membranes: Overcoming the Permeability Barrier Multiple Choice
... [Show More] Questions 1) Of the following molecules, which would not be expected to be moved across a membrane by simple diffusion? A) oxygen B) fatty acids C) water D) glucose E) dimethylurea Answer: D 2) One mechanism by which ions are specifically transported into the cell is the A) gated channel. B) alternating conformation model. C) carrier protein transport. D) uniport transport model. E) all of the above Answer: A 3) In examining glucose transport into a cell, the immediate phosphorylation of glucose following its entry into the cell A) keeps the glucose from being transported back out of the cell. B) allows the cell to maintain higher levels of glucose outside the cell. C) converts glucose into a form for use in cellular respiration. D) converts glucose into a form to be stored. E) all of the above Answer: E 4) In bacteria, the porins have the unique ability to transport A) all hydrophilic molecules. B) hydrophilic molecules of a particular size. C) all hydrophobic molecules. D) hydrophobic molecules of a particular size. E) any molecule, regardless of properties or size. Answer: B 5) In the kidney, the specialized transport proteins that allow for very rapid fluid movement into or out of cells are known as A) aquaporins. B) porins. C) ionophores. D) anion exchange proteins. E) osmosins. Answer: A Contact: royfields212@gmail.com 6) In all organisms, active transport across a membrane requires A) equal concentrations of ions on both sides of the membrane. B) a resting potential of 0 mV. C) exergonic movement indicated by the direction of the electrochemical potential. D) an asymmetric distribution of ions across a membrane. E) both choices B and D Answer: D 7) The movement of water through a membrane, from an area of high concentration to an area of low concentration, is known as A) active transport. B) facilitated transport. C) passive transport. D) osmosis. E) photolysis. Answer: D 8) Which of the following measures is used to determine a substance's polarity? A) partition coefficient B) extinction coefficient C) polarity factor D) asymmetrical distribution points E) polarity determining factor Answer: A 9) Which of the following is/are true with regard to water movement in osmosis? A) hypotonic → hypertonic B) hypertonic → hypotonic C) isotonic → hypotonic D) hypertonic → isotonic E) both choices C and D Answer: A 10) You are wanting to modify plant cells. With the procedure you are using, the plant cells must be in a plasmolyzed state. This means that the plant cells must be placed in a(n) A) acid solution. B) hypotonic solution. C) isotonic solution. D) basic solution. E) hypertonic solution. Answer: E 11) You wish to dehydrate a piece of meat using solutions of varying salt concentrations. The best concentration to use would be A) 0.01%. B) 0.09%. C) 0.9%. D) 1%. E) 10%. Answer: E 12) Which of the following is not a characteristic of passive transport? A) It requires binding of the molecule to be transported. B) It is specific for the molecule being transported. C) The energy for transport is generated by the gradient of the substance being transported. D) The energy for transport is generated by the molecular bonds of the substance being transported. E) Transport of the substance is the result of a conformational change. Answer: D 13) Which of the following glucose transporters in humans has properties that facilitate glucose transport out of the cell in response to keeping blood sugar levels homeostatic? A) GLUT1 B) GLUT2 C) GLUT3 D) GLUT4 E) GLUT5 Answer: B 14) When transporting uncharged molecules across the membrane, which of the following is/are false? A) Keq is always equal to one. B) ΔG is not dependent upon a gradient. C) Movement requires a transport protein. D) ΔG° is always equal to zero. E) both choices A and B Answer: B 15) When transporting charged molecules across a membrane, which of the following is/are true? A) When moving chloride ions in nerve cells, the movement is with both concentration and electrochemical gradients. B) ΔG is dependent on electrochemical potential. C) Keq is always equal to zero. D) ΔG° is always equal to one. E) Membrane potential is not a factor. Answer: B 16) Which of the following is not an example of facilitated diffusion? A) GLUT1 glucose transporter B) anion exchange protein C) aquaporins D) channel proteins E) oxygen transport Answer: E 17) The chloride-bicarbonate antiport is thought to function by which of the following mechanisms? A) "ping-pong" B) "ying-yang" C) uniport dichotomy D) active transport E) induced-fit model Answer: A 18) Facilitated diffusion implies that energy in which form is NOT required? A) ATP B) oxygen C) Na+ D) glucose E) light Answer: A Base your answers to the questions on the following information: For a particular cell, the concentration of sucrose is 10 mM on the inside of the cell and 0.5 mM on the outside, whereas the concentration of sodium ions (Na ) is 0.5 mM on the inside ⁺ of the cell and 10 mM on the outside. The membrane potential is -150 mV, and the temperature is 25°C. Constants: R = 1.987 cal/mol degree; T = 25°C = 298 K; F = 23,062 cal/mole volt 19) What is the ∆G′ for the inward transport of sucrose? A) +1.774 kcal/mol; an endergonic reaction B) +1.774 kcal/mol; an exergonic reaction C) -1.774 kcal/mol; an endergonic reaction D) -1.774 kcal/mol; an exergonic reaction E) none of the above Answer: A 20) What is the ∆G′ for the inward transport of sodium ions? A) +5.233 kcal/mol; an endergonic reaction B) +5.233 kcal/mol; an exergonic reaction C) -5.233 kcal/mol; an endergonic reaction D) -5.233 kcal/mol; an exergonic reaction E) none of the above Answer: D 21) What would be the net ∆G′ for the coupling of these two reactions? A) +7.007 kcal/mol B) +3.459 kcal/mol C) -1.774 kcal/mol D) -3.459 kcal/mol E) -7.007 kcal/mol Answer: D Base your answers to the questions below on the following information: A cell biologist interested in the transport of calcium ions (C a2+) across the plasma membrane of bacterial cells made the following measurements on bacterial cells at 25°C: Vm = -150 mV[Ca2+] inside = 20 mM [C a2+] outside = 0.4 mM 22) What is the free energy change for the inward movement of calcium ions into the bacterial cell? A) +4.6 kcal/mol; an endergonic reaction B) +4.6 kcal/mol; an exergonic reaction C) -4.6 kcal/mol; an endergonic reaction D) -4.6 kcal/mol; an exergonic reaction E) none of the above Answer: D 23) Assuming no change in either the internal or external calcium ion concentration, at what membrane potential would there be no net movement of calcium across the membrane? A) -25 mV B) -50 mV C) 0 mV D) +25 mV E) +50 mV Answer: B 24) The bacteriorhodopsin proton pump creates a proton gradient that is needed in the process of anoxygenic photosynthesis. The energy necessary to drive this pump is generated by A) the rhodopsin pigment directly. B) the proton gradient itself. C) GTP hydrolysis. D) ATP hydrolysis. E) light energy. Answer: E 25) Cystic fibrosis is the result of a malfunction of the cell in transporting which of the following ions? A) ClB) K+ C) Na+ D) glucose E) OHAnswer: A 26) In some cells, it was noted that water moved faster than could be accounted for by simple diffusion. From this information, which of the following were identified and characterized? A) hydroporins B) glycoporins C) facilitator porins D) lipoporins E) aquaporins Answer: E 27) Which of the following is not a characteristic of active transport? A) sensitive to metabolic poisons B) exclusively move one molecule at a time in a unidirectional manner C) can be coupled with passive transport to generate the energy necessary for active transport D) can work as symports or antiports E) all of the above Answer: B 28) Which of the following is not a mechanism of active transport? A) coupled transport B) ATP hydrolysis-driven pump C) unidirectional movement with gradients D) light-driven pumps E) both choices C and D Answer: C 29) Which type of ATPase is associated with the integral binding of ATP as part of the transport process? A) ABC type B) F type C) P type D) V type Answer: A 30) The P-type ATPases associated with the movement of heavy metals are A) type 1. B) type 2. C) type 3. D) type 4. E) type 5. Answer: A 31) While working with a novel cell line, you observe that movement of hydrophobic molecules, such as cholesterol and fatty acids, is impaired. You narrow the defect down to a P-type ATPase A) type 1. B) type 2. C) type 3. D) type 4. E) type 5. Answer: D 32) The Na+/K+ pump actively moves A) 2 Na+ in, 3 K+ out. B) 2 Na+ out, 3 K+ in. C) 3 Na+ in 2 K+ out. D) 3 Na+ out, 2 K+ in. E) 1 Na+ out, 1 K+ in. Answer: D 33) An example of indirect active transport is A) Na+/K+ pumps. B) P-type ATPases. C) ABC-type ATPases. D) Na+/glucose symport. E) both choices B and C Answer: D A researcher is interested in the mode of transport across the cell membrane of three different substances: A, B, and C. His data are reported in the graphs associated with the following questions. Figure 8.1 34) The graph above shows the initial rate of transport for each substance when the cells are placed in solutions of different concentrations of A, B, and C. Based on these data, substance A is transported via A) active transport. B) facilitated transport. C) passive transport. D) simple diffusion. E) choices A, B, and C Answer: D 35) Based on the same graph, substances B and C A) show saturation kinetics. B) are transported by a transporter protein. C) do not move by simple diffusion. D) choices A and B only E) all of the above Answer: E 36) The graph below shows the rate of transport for each substance when the cells are placed in 0.10 mM solutions of A, B, and C. Based on these data and coupled with the data observed above, substance C is transported via ________. Figure 8.2 A) active transport B) facilitated transport C) passive transport D) simple diffusion E) choices A, B, and C Answer: A 37) The primary difference between active transport and facilitated diffusion is that active transport is the only one in which A) [S]high → [S]low. B) transporter proteins are required. C) [S]low → [S]high. D) the concentration gradient provides the necessary energy for movement. E) only water molecules move. Answer: C 38) Animal cells use exocytosis to secrete all of the following except A) cell wall material. B) mucus. C) peptide hormones. D) milk proteins. E) digestive enzymes. Answer: A 39) Mutations in bacterial porins can lead to antibiotic resistance typically by A) closing the α-helix of the porin. B) limiting the passage of nonpolar substances. C) blocking entry of the antibiotic. D) disrupting the voltage of the gated channel. E) all of the above Answer: C 40) A special class of ABC-type ATPases associated with tumors that allow movement of antibiotics and other drugs out of the cell are known as A) multidrug resistance transport protein. B) import transporter proteins. C) cystic fibrosis transmembrane conductance regulator. D) human catalytic convertase. E) none of the above; no such transporter has been identified in eukaryotes. Answer: A Matching Questions Choose the item in column 2 that best matches each item in column 1. A) diffusion and passive and active transport B) both passive and active transport C) diffusion D) active transport E) none of the listed processes F) both diffusion and passive transport G) indirect active transport H) passive transport 1) requires a specific integral membrane protein 2) dependent on solubility properties of the solute 3) requires cellular expenditure of energy 4) Keq = 1 5) Na+/glucose symport 6) Na+/K+ pump 7) exclusively involves the transfer of small, nonpolar molecules 8) applies only to ions 9) ΔG° = 0 10) direction of transport is dependent upon the concentration gradient at any given point in time 11) requires ligand binding and therefore Michaelis constants can be calculated Answers: 1) A 2) C 3) D 4) A 5) G 6) D 7) C 8) E 9) A 10) F 11) B Short Answer Questions 1) Transmembrane movement of a substance against a concentration gradient is called ________. Answer: active transport 2) Transmembrane movement of a substance with a concentration gradient utilizing a membrane protein is called ________. Answer: passive transport or facilitated transport 3) Transmembrane movement of a substance with a concentration gradient, with no involvement of membrane proteins, is called ________. Answer: diffusion 4) The transport of two molecules across the cell membrane in the same direction is called ________. Answer: symport 5) The transport of two molecules across the cell membrane in different directions is called ________. Answer: antiport 6) The type of transport ATPase found in bacteria, mitochondria, and chloroplasts are the ________ ATPases. Answer: F-type 7) The type of transport ATPase that are reversibly phosphorylated as part of the transport mechanism are the ________ ATPases. Answer: P-type 8) Uptake of food particles by trapping them within an invagination of the plasma membrane is called ________. Answer: endocytosis 9) A(n) ________ solution is one that contains a solute concentration that is ________ than that within the cell and results in the "bursting" of the cell. Answer: hypotonic, lower 10) Receptor-mediated endocytosis involves vesicles with a special coat protein known as ________. Answer: clathrin 11) In the capillaries of the body tissues, CO2 diffuses ________ and is converted to ________. Answer: inward; bicarbonate 12) In the capillaries of the lungs, O2 diffuses ________ and is bound to ________. Answer: inward; hemoglobin 13) Pores of the outer membrane of bacteria, mitochondria, and chloroplasts that are less specific and are formed by multipass transmembrane proteins are called ________. Answer: porins Inquiry 1) What are the two most important properties that allow a molecule to cross a phospholipid bilayer by simple diffusion? What are two such molecules? Answer: The two most important properties are size (small) and being nonpolar. A variety of examples are possible answers, including oxygen, water, carbon dioxide, and ethanol. 2) Brucella abortus is a bacterium that utilizes an unusual sugar, erythritol. The concentration of erythritol within the B. abortus cell is 10 mM, while the external erythritol concentration is at very low levels, such as 0.20 mM. What is the energy requirement for the inward transport of erythritol at 37°C under these conditions? Answer: Begin with the equation: ΔG inward = + R T ln [S] outside [S]inside As R = 1.987 cal/mol-K and T = K = °C + 273, the above equation is: ΔG inward = + (1.987) (37 + 273) ln = 615.97 ln 50 = 2409.69 cal/mol = +2.41 kcal/mol 3) How would known cancer cells that possess multidrug resistance transport proteins affect cancer treatment? How might you potentially counter the effect of such transporters? Answer: Although answers will vary, the students should discuss the mechanism whereby the transporter removes the drug before it could potentially have an effect on the cancer cells. Further, they should hypothesize that treatments that prevent functioning of the MDR transport protein, such as monoclonal antibody binding of the transport protein or prior treatment of the cells with a competitive or noncompetitive inhibitor followed by drug treatment, are possible. Evaluate integrity of other possible answers. 4) Consider the glucose transporters (GLUT). In the case of GLUT1, glucose is transported into the cell for use by the cell. On the other hand, GLUT2 in liver cells allows for glucose to be released by the cells. Why would the body need GLUT systems with such variation? Answer: GLUT1 recognizes glucose and brings it into the cell for cellular activities in red blood cells. Many cells have GLUT proteins associated with glucose import. However, in the case of the liver, the cells sometimes need to release glucose in order to maintain homeostasis with regard to blood sugar levels. 5) Design an experiment whereby you would be able to distinguish between simple diffusion and facilitated diffusion of a substance. (Include graphs, if this aids in your discussion.) Answer: Basically all student responses should include the observation that, with simple diffusion, increasing solute concentrations lead to increased crossing of the cell membrane in a linear fashion. On the other hand, if facilitated diffusion occurs, one will observe saturation kinetics. [Show Less]