Campbell Biology, 10e (Reece)
Chapter 7 Membrane Structure and Function
1) For a protein to be an integral membrane protein, it would have to be _____.
A) hydrophilic
B) hydrophobic
C) amphipathic, with at least one hydrophobic region
D) exposed on only one surface of the membrane
2) You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids.
After testing the permeability of this membrane to glucose, you increase the proportion of
unsaturated phospholipids in the bilayer. What will happen to the membrane’s permeability to
glucose?
A) Permeability to glucose will increase.
B) Permeability to glucose will decrease.
C) Permeability to glucose will stay the same.
D) You cannot predict the outcome. You simply have to make the measurement.
3) According to the fluid mosaic model of cell membranes, phospholipids _____.
A) can move laterally along the plane of the membrane
B) frequently flip-flop from one side of the membrane to the other
C) occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the
membrane
D) have hydrophilic tails in the interior of the membrane
4) The membranes of winter wheat are able to remain fluid when it is extremely cold by _____.
A) increasing the percentage of unsaturated phospholipids in the membrane
B) increasing the percentage of cholesterol molecules in the membrane
C) decreasing the number of hydrophobic proteins in the membrane
D) cotransport of glucose and hydrogen
2
5) Some regions of the plasma membrane, called lipid rafts, have a higher concentration of
cholesterol molecules. At higher temperatures, these regions _____.
A) are more fluid than the surrounding membrane
B) are less fluid than the surrounding membrane
C) detach from the plasma membrane and clog arteries
D) have higher rates of lateral diffusion of lipids and proteins into and out of these regions
6) Singer and Nicolson’s fluid mosaic model of the membrane proposed that membranes_____.
A) are a phospholipid bilayer between two layers of hydrophilic proteins
B) are a single layer of phospholipids and proteins
C) consist of protein molecules embedded in a fluid bilayer of phospholipids
D) consist of a mosaic of polysaccharides and proteins
7) An animal cell lacking oligosaccharides on the external surface of its plasma membrane would
likely be impaired in which function?
A) transporting ions against an electrochemical gradient
B) cell-cell recognition
C) attaching the plasma membrane to the cytoskeleton
D) establishing a diffusion barrier to charged molecules
8) Which of these are NOT embedded in the hydrophobic portion of the lipid bilayer at all?
A) transmembrane proteins
B) integral proteins
C) peripheral proteins
D) All of these are embedded in the hydrophobic portion of the lipid bilayer.
9) Why are lipids and proteins free to move laterally in membranes?
A) The interior of the membrane is filled with liquid water.
B) Lipids and proteins repulse each other in the membrane.
C) Hydrophilic portions of the lipids are in the interior of the membrane.
D) There are only weak hydrophobic interactions in the interior of the membrane.
For the following questions, match the labeled component of the cell membrane in the
figure with its description.
10) Which component is a peripheral protein?
A) A
B) B
C) C
D) D
11) Which component is cholesterol?
A) B
B) C
C) D
D) E
12) Which component is a protein fiber of the extracellular matrix?
A) A
B) B
C) C
D) E
13) Which component is a microfilament (actin filament) of the cytoskeleton?
A) A
B) B
C) C
D) D
14) Which component is a glycolipid?
A) A
B) B
C) C
D) E
15) Cell membranes are asymmetrical. Which of the following statements is the most likely
explanation for the membrane’s asymmetrical nature?
A) Since the cell membrane forms a border between one cell and another in tightly packed
tissues such as epithelium, the membrane must be asymmetrical
B) Since cell membranes communicate signals from one organism to another, the cell
membranes must be asymmetrical.
C) The two sides of a cell membrane face different environments and carry out different
functions.
D) Proteins only function on the cytoplasmic side of the cell membrane, which results in the
membrane’s asymmetrical nature.
16) In what way do the membranes of a eukaryotic cell vary?
A) Phospholipids are found only in certain membranes.
B) Certain proteins are unique to each membrane.
C) Only certain membranes of the cell are selectively permeable.
D) Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have
hydrophilic surfaces facing the cytoplasm.
17) Which of the following is a reasonable explanation for why unsaturated fatty acids help keep
a membrane more fluid at lower temperatures?
A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing
tightly.
B) Unsaturated fatty acids have a higher cholesterol content and, therefore, more cholesterol in
membranes.
C) Unsaturated fatty acids are more polar than saturated fatty acids.
D) The double bonds block interaction among the hydrophilic head groups of the lipids.
18) What kinds of molecules pass through a cell membrane most easily?
A) large and hydrophobic
B) small and hydrophobic
C) large polar
D) ionic
19) Which of the following most accurately describes selective permeability?
A) An input of energy is required for transport.
B) Lipid-soluble molecules pass through a membrane.
C) There must be a concentration gradient for molecules to pass through a membrane.
D) Only certain molecules can cross a cell membrane.
20) Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
A) It exhibits a specificity for a particular type of molecule.
B) It requires the expenditure of cellular energy to function.
C) It works against diffusion.
D) It has no hydrophobic regions.
21) Which of the following would likely move through the lipid bilayer of a plasma membrane
most rapidly?
A) CO2
B) an amino acid
C) glucose
D) K+
22) Which of the following allows water to move much faster across cell membranes?
A) the sodium-potassium pump
B) ATP
C) peripheral proteins
D) aquaporins
23) You are working on a team that is designing a new drug. For this drug to work, it must enter
the cytoplasm of specific target cells. Which of the following would be a factor that determines
whether the molecule selectively enters the target cells?
A) hydrophobicity of the drug molecule
B) lack of charge on the drug molecule
C) similarity of the drug molecule to other molecules transported by the target cells
D) lipid composition of the target cells’ plasma membrane
24) Diffusion _____.
A) is very rapid over long distances
B) requires an expenditure of energy by the cell
C) is a passive process in which molecules move from a region of higher concentration to a
region of lower concentration
D) requires integral proteins in the cell membrane
25) Which of the following processes includes all others?
A) osmosis
B) facilitated diffusion
C) passive transport
D) transport of an ion down its electrochemical gradient
26) When a cell is in equilibrium with its environment, which of the following occurs for
substances that can diffuse through the cell?
A) There is random movement of substances into and out of the cell.
B) There is directed movement of substances into and out of the cell.
C) There is no movement of substances into and out of the cell.
D) All movement of molecules is directed by active transport.
27) Which of the following is true of osmosis?
A) Osmosis only takes place in red blood cells.
B) Osmosis is an energy-demanding or “active” process.
C) In osmosis, water moves across a membrane from areas of lower solute concentration to areas
of higher solute concentration.
D) In osmosis, solutes move across a membrane from areas of lower water concentration to areas
of higher water concentration.
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.
28) Refer t o the figure. Initially, in terms of tonicity, the solution in side A with respect to the
solution in side B is _____.
A) hypotonic
B) isotonic
C) saturated
D) hypertonic
29) Refer to the figure. After the system reaches equilibrium, what changes are observed?
A) The molarity of sucrose is higher than that of glucose on side A.
B) The water level is higher in side A than in side B.
C) The water level is unchanged.
D) The water level is higher in side B than in side A.
30) A patient was involved a serious accident and lost a large quantity of blood. In an attempt to
replenish body fluids, distilled water—equal to the volume of blood lost—is added to the blood
directly via one of his veins. What will be the most probable result of this transfusion?
A) The patient’s red blood cells will shrivel up because the blood has become hypotonic
compared to the cells.
B) The patient’s red blood cells will swell and possibly burst because the blood has become
hypotonic compared to the cells.
C) The patient’s red blood cells will shrivel up because the blood has become hypertonic
compared to the cells.
D) The patient’s red blood cells will burst because the blood has become hypertonic compared to
the cells.
31) Refer to the figure. At the beginning of the experiment,
A) side A is hypertonic to side B.
B) side A is hypotonic to side B.
C) side A is hypertonic to side B with respect to glucose.
D) side A is hypotonic to side B with respect to NaCl.
32) Refer to the figure. If you examine side A after three days, you should find _____.
A) a decrease in the concentration of NaCl and glucose and an increase in the water level
B) a decrease in the concentration of NaCl, an increase in water level, and no change in the
concentration of glucose
C) a decrease in the concentration of NaCl and a decrease in the water level
D) no change in the concentration of NaCl and glucose and an increase in the water level
Five dialysis bags constructed of membrane, which 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.
33) Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M
solution at the beginning of the experiment?
A) A
B) B
C) C
D) D
34) Which line in the graph represents the bag with the highest initial concentration of sucrose?
A) A
B) B
C) C
D) D
35) Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at
50 minutes?
A) A and B
B) B
C) D
D) D and E
36) 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_____.
A) and the salt solution are both hypertonic to the cells of the celery stalks
B) is hypotonic and the salt solution is hypertonic to the cells of the celery stalks
C) is hypertonic and the salt solution is hypotonic to the cells of the celery stalks
D) is isotonic and the salt solution is hypertonic to the cells of the celery stalks
37) What will happen to a red blood cell (RBC), which has an internal ion concentration of about
0.9 percent, if it is placed into a beaker of pure water?
A) The cell would shrink because the water in the beaker is hypotonic relative to the cytoplasm
of the RBC.
B) The cell would shrink because the water in the beaker is hypertonic relative to the cytoplasm
of the RBC.
C) The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of
the RBC.
D) The cell will remain the same size because the solution outside the cell is isotonic.
38) Which of the following statements correctly describes the normal tonicity conditions for
typical plant and animal cells? The animal cell is in _____.
A) a hypotonic solution, and the plant cell is in an isotonic solution
B) an isotonic solution, and the plant cell is in a hypertonic solution
C) a hypertonic solution, and the plant cell is in an isotonic solution
D) an isotonic solution, and the plant cell is in a hypotonic solution
39) In which of the following would there be the greatest need for osmoregulation?
A) an animal connective tissue cell bathed in isotonic body fluid
B) a salmon moving from a river into an ocean
C) a red blood cell surrounded by plasma
D) a plant being grown hydroponically in a watery mixture of designated nutrients
40) When a plant cell, such as one from a rose stem, is submerged in a very hypotonic solution,
what is likely to occur?
A) The cell will burst.
B) Plasmolysis will shrink the interior.
C) The cell will become flaccid.
D) The cell will become turgid.
41) A sodium-potassium pump _____.
A) moves three potassium ions out of a cell and two sodium ions into a cell while producing an
ATP for each cycle
B) move three sodium ions out of a cell and two potassium ions into a cell while consuming an
ATP for each cycle
C) moves three potassium ions out of a cell and two sodium ions into a cell while consuming 2
ATP in each cycle
D) move three sodium ions out of a cell and two potassium ions into a cell and generates an ATP
in each cycle
42) The sodium-potassium pump is called an electrogenic pump because it _____.
A) pumps equal quantities of Na+ and K+ across the membrane
B) contributes to the membrane potential
C) ionizes sodium and potassium atoms
D) is used to drive the transport of other molecules against a concentration gradient
43) Which of the following membrane activities requires energy from ATP?
A) facilitated diffusion of chloride ions across the membrane through a chloride channel
B) movement of Na+ ions from a lower concentration in a mammalian cell to a higher
concentration in the extracellular fluid
C) movement of glucose molecules into a bacterial cell from a medium containing a higher
concentration of glucose than inside the cell
D) movement of carbon dioxide out of a paramecium
44) The voltage across a membrane is called the _____.
A) chemical gradient
B) membrane potential
C) osmotic potential
D) electrochemical gradient
45) Ions diffuse across membranes through specific ion channels down _____.
A) their chemical gradients
B) their concentration gradients
C) the electrical gradients
D) their electrochemical gradients
46) Which of the following would increase the electrochemical gradient across a membrane?
A) a sucrose-proton cotransporter
B) a proton pump
C) a potassium channel
D) both a proton pump and a potassium channel
47) 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. Phosphate transport is an example of _____.
A) passive diffusion
B) facilitated diffusion
C) active transport
D) cotransport
14
48) 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 _____.
A) cotransport proteins
B) ion channels
C) pores in the plasma membrane
D) passive diffusion across the plasma membrane
49) Which of the following is most likely true of a protein that cotransports glucose and sodium
ions into the intestinal cells of an animal?
A) Sodium and glucose compete for the same binding site in the cotransporter.
B) Glucose entering the cell down its concentration gradient provides energy for uptake of
sodium ions against the electrochemical gradient.
C) Sodium ions can move down their electrochemical gradient through the cotransporter whether
or not glucose is present outside the cell.
D) A substance that blocks sodium ions from binding to the cotransport protein will also block
the transport of glucose.
50) Proton pumps are used in various ways by members of every domain of organisms: Bacteria,
Archaea, and Eukarya. What does this most probably mean?
A) Proton gradients across a membrane were used by cells that were the common ancestor of all
three domains of life.
B) The high concentration of protons in the ancient atmosphere must have necessitated a pump
mechanism.
C) Cells of each domain evolved proton pumps independently when oceans became more acidic.
D) Proton pumps are necessary to all cell membranes.
51) Several epidemic microbial diseases of earlier centuries incurred high death rates because
they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal
because we have developed which of the following?
A) antiviral medications that are efficient and work well with most viruses
B) intravenous feeding techniques
C) medications to slow blood loss
D) hydrating drinks with high concentrations of salts and glucose
52) The force driving simple diffusion is _____, while the energy source for active transport is
_____.
A) the concentration gradient; ADP
B) the concentration gradient; ATP
C) transmembrane pumps; electron transport
D) phosphorylated protein carriers; ATP
53) An organism with a cell wall would most likely be unable to take in materials through _____.
A) osmosis
B) active transport
C) phagocytosis
D) facilitated diffusion
54) White blood cells engulf bacteria using _____.
A) phagocytosis
B) pinocytosis
C) osmosis
D) receptor-mediated exocytosis
55) Familial hypercholesterolemia is characterized by _____.
A) defective LDL receptors on the cell membranes
B) poor attachment of the cholesterol to the extracellular matrix of cells
C) a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes
D) inhibition of the cholesterol active transport system in red blood cells
56) The difference between pinocytosis and receptor-mediated endocytosis is that _____.
A) pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis
brings in other molecules as well.
B) pinocytosis increases the surface area of the plasma membrane, whereas receptor-mediated
endocytosis decreases the plasma membrane surface area.
C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated
endocytosis offers more selectivity.
D) pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated
endocytosis cannot.
57) In receptor-mediated endocytosis, receptor molecules initially project to the outside of the
cell. Where do they end up after endocytosis?
A) on the outside of vesicles
B) on the inside surface of the cell membrane
C) on the inside surface of the vesicle
D) on the outer surface of the nucleus
58) A bacterium engulfed by a white blood cell through phagocytosis will be digested by
enzymes contained in _____.
A) lysosomes
B) Golgi vesicles
C) vacuoles
D) secretory vesicles
17
Use the paragraph and accompanying figure to answer the following questions.
Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface
molecules. The viral nucleic acid molecules are enclosed in a protein capsid, and the protein
capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral
glycoproteins. One hypothesis for viral entry into cells is that binding of HIV membrane
glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma
membrane, releasing the viral capsid into the cytoplasm. An alternative hypothesis is that HIV
gains entry into the cell via receptor-mediated endocytosis, and membrane fusion occurs in the
endocytotic vesicle. To test these alternative hypotheses for HIV entry, researchers labeled the
lipids on the HIV membrane with a red fluorescent dye.
59) In an HIV-infected cell producing HIV virus particles, the viral glycoprotein is expressed on
the plasma membrane. How do the viral glycoproteins get to the plasma membrane? They are
synthesized _____.
A) on ribosomes on the plasma membrane
B) by ribosomes in the rough ER and arrive at the plasma membrane in the membrane of
secretory vesicles
C) on free cytoplasmic ribosomes and then inserted into the plasma membrane
D) by ribosomes in the rough ER, secreted from the cell, and inserted into the plasma membrane
from the outside
60) What would be observed by live-cell fluorescence microscopy immediately after HIV entry
if HIV is endocytosed first, and then later fuses with the endocytotic vesicle membrane?
A) A spot of red fluorescence will be visible on the infected cell’s plasma membrane, marking
the site of membrane fusion and HIV entry.
B) The red fluorescent dye-labeled lipids will appear in the infected cell’s interior.
C) A spot of red fluorescence will diffuse in the infected cell’s cytoplasm.
D) A spot of red fluorescence will remain outside the cell after delivering the viral capsid.
61) Three lab groups carried out an experiment to identify the correct molarities for five
solutions. Each unknown contained one of the following sucrose concentrations: 0.0 M, 0.2 M,
0.4 M, 0.6 M, 0.8 M, and 1.0 M. Each data entry represents the average of 3 sample replications
of 1 cm3 sweet potato cubes expressed as percent change in mass after an overnight (24 hr) soak
in the unknown solutions. From the data given, which statement most accurately describes what
is occurring in response to a particular unknown solution.
A) Unknown solution E contains the highest concentration of sucrose and the change in mass is
due to the active transport of sucrose into the cell in exchange for water molecules.
B) Osmosis of water molecules from unknown solution A likely caused the increase in mass
observed.
C) Passive transport of sucrose out of the potato cells explains the change in mass observed for
unknown solution F.
D) Unknown solution C represents a sucrose molarity slightly lower than the molarity of sweet
potato cells, thus water is transported out of the cells.