Physiology
- Chapter 4-Cell movement of molecules across cell membrane
- Which of the following statements regarding the structure and function of cell membranes is correct?
A.The phospholipid bilayer is arranged so that the hydrophilic heads of the phospholipid molecule face the extra- and intracellular fluids.
B.Some proteins integrated into the membrane serve as channels for the passage of nonpolar molecules through the membrane.
C.Some proteins integrated into the membrane function as channels associated with transport of ions through the membrane.
D.Both the phospholipid bilayer is arranged so that the hydrophilic heads of the phospholipid molecule face the extra- and intracellular fluids and some proteins integrated into the membrane function as channels associated with transport of ions through the membrane are correct.
E.All of the choices are correct.
2. Diffusion
A.depends upon the random motion of molecules.
B.results in net movement of molecules from regions of low concentration to regions of high concentration.
C.is important for moving molecules over large distances in the body.
D.requires energy in the form of ATP to be carried out.
E.Includes all of the choices.
3. When a solute, X, is placed in compartment A of a two compartment container and allowed to diffuse to compartment B and attain diffusion equilibrium, then
A. there will no longer be any movement of solutes between compartments.
B. solutes will be moving in both directions equally.
C. solutes will only continue to move from A to B
D. solutes will only continue to move from B toE.
E. solutes will continue to move to the side with the higher concentration
4. Which of the following statements regarding the diffusion of nonpolar solutes across cell membranes is correct?
A. At equilibrium for solute X, the flux of X across cell membranes is zero
B. At equilibrium for solute X, the net flux of X across cell membranes is zero
C. At equilibrium for solute X, the concentration of X inside the cell is equal to its concentration outside the cell.
D. Both at equilibrium for solute X, the flux of X across cell membranes is zero and at equilibrium for solute X, the concentration of X inside the cell is equal to its concentration outside the cell are correct.
E. Both at equilibrium for solute X, the net flux of X across cell membranes is zero and at equilibrium for solute X, the concentration of X inside the cell is equal to its concentration outside the cell are correct.
5. The net flux of a penetrating solute into a cell will increase if the
A. permeability constant for that solute
B. temperature increases.
C. concentration of that solute in the extracellular fluid
D. Both permeability constant for that solute increases and concentration of that solute in the
extracellular fluid increases are correct.
E. All of the choices are correct
6. Which of the following would decrease the rate of diffusion?
A. increasing the size of the diffusing solute
B. increasing the temperature
C. increasing the concentration gradient
D. increasing the surface area for diffusion
E. All of the choices would increase the rate of diffusion
7. Equal concentrations of two solutes, A and B, are placed into the same beaker at the same time. Solute A reaches diffusion equilibrium faster than solute B. What is the most likely explanation for this observation?
A. The temperature was greater for solute A than solute B
B. The concentration gradient for A was greater than B.
C. Solute A is smaller than solute B
D. Solute A traveled a shorter distance than solute B
E. All of the choices are logical explanation
8. If it takes solute A 1 second to diffuse 1 millimeter, how long will it take solute A to diffuse 10 millimeters under the same conditions?
A. 1 second
B. 10 seconds
C. 50 seconds
D.100 seconds
E.1000 seconds
9. In general, polar molecules diffuse more rapidly through the lipid bilayer part of cell membranes than do nonpolar molecules. This statement is
A. true
B. false. Polar molecules diffuse through less rapidly because the bilayer is polar throughout its width
C. false. Polar molecules diffuse through less rapidly because the bilayer is nonpolar throughout its width
D. false. Nonpolar molecules diffuse through more rapidly because much of the bilayer is nonpolar.
E. The rate of diffusion of nonpolar and polar molecules through the bilayer is essentially the same as long as the molecules are the same size.
10. Which of the following statements regarding the movement of molecules across cell membranes is correct?
A. The diffusion of molecules across a cell membrane occurs at a rate that is influenced by the surface area of the membrane and the magnitude of the concentration difference across it
B. The net flux of molecules that cross cell membranes by diffusion is always from regions of lower concentration to regions of higher concentration
C. Molecules that enter a cell by diffusion must directly permeate the lipid portion of the plasma membrane, whereas those that enter by facilitated diffusion utilize membrane-bound proteins.
D. Both the diffusion of molecules across a cell membrane occurs at a rate that is influenced bythe surface area of the membrane and the magnitude of the concentration difference across it and the net flux of molecules that cross cell membranes by diffusion is always from regions of lower concentration to regions of higher concentration are correct.
E. Both the diffusion of molecules across a cell membrane occurs at a rate that is influenced by the surface area of the membrane and the magnitude of the concentration difference across it and molecules that enter a cell by diffusion must directly permeate the lipid portion of the plasma membrane, whereas those that enter by facilitated diffusion utilize membrane-bound proteins are correct.
11. The permeability of the plasma membrane to mineral ions
A. is dependent upon channels formed by
B. varies from one cell to another.
C. is affected by differences in electrical charge on the two sides of the
D. Both is dependent upon channels formed by proteins and is affected by differences in electrical charge on the two sides of the membrane are correct.
E. All of the choices are correct.
12. Ion channels in cell membranes
A. are nonspecific
B. may open in response to a change in potential difference across the
C. may open in response to binding a ligand.
D. Both are nonspecific and may open in response to a change in potential difference across the membrane are correct.
E. Both may open in response to a change in potential difference across the membrane and may open in response to binding a ligand are correct.
13. The concentration of
A. positively charged substances within cells is greater than the concentration of negatively charged substances.
B. sodium and chloride ions in the extracellular fluid is greater than that in the cytosol of cells.
C. potassium and calcium ions in the cytosol of cells is greater than that in the extracellular fluid.
D. Both positively charged substances within cells is greater than the concentration of negatively charged substances and sodium and chloride ions in the extracellular fluid is greater than that in the cytosol of cells are correct
E. Both sodium and chloride ions in the extracellular fluid is greater than that in the cytosol of cells and potassium and calcium ions in the cytosol of cells is greater than that in the extracellular fluid are correct
14. Mediated transport across cell membranes
A. refers to the movement of ions through protein channel
B. refers both to diffusion and to the active transport of molecules
C. is characterized by saturable carriers and a maximum velocity of transport
D. Both refers to the movement of ions through protein channels and refers both to diffusion and to the active transport of molecules are correct
E. Both refers both to diffusion and to the active transport of molecules and is characterized by saturable carriers and a maximum velocity of transport are correct
15. Carrier- mediated transport
A. involves a specific membrane protein that functions as a carrier molecule
B. always involves the movement of substances against a concentration gradient
C. always requires the direct expenditure of energy.
D. Both involves a specific membrane protein that functions as a carrier molecule and always involves the movement of substances against a concentration gradient are correct
E. All of the choices are correct
16. Which of the following is a feature that distinguishes active transport from facilitated diffusion?
A. saturability
B. requirement for a carrier molecule
C. specificity
D. presence of a transport maximum
E. requirement for metabolic energy
17. The mediated transport of a substance across a plasma membrane
A. depends upon the binding of that substance to a specific site on the membrane protein
B. depends upon movement of proteins from one side of the membrane to the other.
C. always increases in direct proportion to the increasing concentration of the substance on one side of the membrane.
D. Both depends upon the binding of that substance to a specific site on the membrane protein and depends upon movement of proteins from one side of the membrane to the other are correct
E. All of the choices are
18. Which of the following statements regarding the active transport of molecules across cell membranes is correct?
A. Both primary and secondary active transport are dependent upon energy derived from ATP
B. In secondary active-transport systems in which Na ions are bound to carriers, the actively transported solute always follows Na ions across the membrane.
C. 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.
D. Both primary and secondary active transport are dependent upon energy derived from ATP and in secondary active-transport systems in which Na ions are bound to carriers, the actively transported solute always follows Na ions across the membrane are correct
E. Both primary and secondary active transport are dependent upon energy derived from ATP and 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 are correct.
19. Glucose enters most cells by
A. diffusion through the lipid
B. primary active transport.
C. secondary active
D. diffusion through a protein channel.
E. endocytosis
20. Which of the following is not a difference between primary active transport and secondary active transport?
A. Primary active transport uses energy derived from ATP whereas secondary active transport does not
B. Primary active transport uses a carrier that is an ATPase whereas the latter does not
C. Primary active transport uses a carrier that is phosphorylated whereas the latter does not
D. Primary active transport uses a carrier whose binding affinity for the solute is modified by covalent modulation whereas the latter does not
E. None of the choices are correct.