Biology, 7e (Campbell) Chapter 7: Membrane Structure and Function Chapter Questions
A.H.DavsonandJ.Danielli
B.I.Langmuir
C.C.Overton
D.S.SingerandG.Nicolson
E.E.GorterandF.Grendel
2) Membranes are a phospholipid bilayer between two layers of hydrophilic proteins. Answer: A
3) The membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.
Answer: D
4) Which of the following types of molecules are the major structural components of the cell
membrane? A) phospholipids and cellulose B) nucleic acids and proteins C) phospholipids and
proteins D) proteins and cellulose E) glycoproteins and cholesterol
For the following questions, match the labeled component of the cell membrane (Figure 7.1)
with its description. Figure 7.1
Figure7.1
5) peripheral protein Answer: D
6) cholesterol Answer: E
7) fiber of the extracellular matrix Answer: A
8) microfilament of the cytoskeleton Answer: C
9) glycolipid Answer: B
10) When biological membranes are frozen and then fractured, they tend to break along the
middle of the bilayer. The best explanation for this is that A) the integral membrane proteins are
not strong enough to hold the bilayer together. B) water that is present in the middle of the
bilayer freezes and is easily fractured. C) hydrophilic interactions between the opposite
membrane surfaces are destroyed on freezing. D) the carbon-carbon bonds of the phospholipid
tails are easily broken. E) the hydrophobic interactions that hold the membrane together are
weakest at this point.
11) All of the following molecules are part of the cell membrane except A) lipids. B) nucleic
acids. C) proteins. D) phosphate groups. E) steroids.
12) The original model for the bilayer structure of cell membranes, which was prepared in the
1920s, was based on which of the following? A) detailed electron micrographs of freezefractured membranes B) the presence of proteins as a functional component of biological
membranes C) the observation that all membranes contain phospholipids and proteins D) the
understanding that phospholipids are amphipathic molecules E) A and B only
13) The presence of cholesterol in the plasma membranes of some animals A) enables the
membrane to stay fluid more easily when cell temperature drops. B) enables the animal to
remove hydrogen atoms from saturated phospholipids. C) enables the animal to add hydrogen
atoms to unsaturated phospholipids. D) makes the membrane less flexible, allowing it to sustain
greater pressure from within the cell. E) makes the animal more susceptible to circulatory
disorders.
14) According to the fluid mosaic model of cell membranes, which of the following is a true
statement about membrane phospholipids? A) They can move laterally along the plane of the
membrane. B) They frequently flip-flop from one side of the membrane to the other. C) They
occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the
membrane. D) They are free to depart from the membrane and dissolve in the surrounding
solution. E) They have hydrophilic tails in the interior of the membrane.
15) The lateral mobility (fluidity) of lipids and proteins in membranes is a consequence of A)
lack of covalent bonds between the lipid and protein components of the membrane. B) weak
hydrophobic interactions among the components in the interior of the membrane. C) the presence
of liquid water in the interior of the membrane. D) A and B only E) A, B, and C Answer: D
Topic: Concept 7.1 Skill: Comprehension
16) What is one of the ways that the membranes of winter wheat are able to remain fluid when it
is extremely cold? A) by increasing the percentage of unsaturated phospholipids in the
membrane B) by increasing the percentage of cholesterol molecules in the membrane C) by
decreasing the number of hydrophobic proteins in the membrane D) A and B only E) A, B, and C
Answer: A Topic: Concept 7.1 Skill: Comprehension
17) The surface of an integral membrane protein would be best described as A) hydrophilic. B)
hydrophobic. C) amphipathic. D) completely covered with phospholipids. E) exposed on only
one surface of the membrane.
18) When a membrane is freeze-fractured, the bilayer splits down the middle between the two
layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps
seen on the fractured surface of the membrane are A) peripheral proteins. B) phospholipids. C)
carbohydrates. D) integral proteins. E) cholesterol molecules.
19) All of the following are functions of integral membrane proteins except A) protein synthesis.
B) active transport. C) hormone reception. D) cell adhesion. E) cytoskeleton attachment.
20) Which of the following is a reasonable explanation for why unsaturated fatty acids help keep
any membrane more fluid at lower temperatures? A) The double bonds form a kink in the fatty
acid tail, forcing adjacent lipids to be further apart. B) Unsaturated fatty acids have a higher
cholesterol content. C) Unsaturated fatty acids permit more water in the interior of the
membrane. D) The double bonds block interaction among the hydrophilic head groups of the
lipids. E) The double bonds result in a shorter fatty acid tail.
21) Which of the following is correct about integral membrane proteins? A) They lack tertiary
structure. B) They are loosely bound to the surface of the bilayer. C) They are usually
transmembrane proteins. D) They are not mobile within the bilayer. E) They serve only a
structural role in membranes.
22) Of the following functions, which is most important for the glycoproteins and glycolipids of
animal cell membranes? A) facilitated diffusion of molecules down their concentration gradients
B) active transport of molecules against their concentration gradients C) maintaining the integrity
of a fluid mosaic membrane D) maintaining membrane fluidity at low temperatures E) a cell's
ability to distinguish one type of neighboring cell from another
23) What is one of the functions of cholesterol in animal cell membranes? A) facilitates transport
of ions B) stores energy C) maintains membrane fluidity D) speeds diffusion E) phosphorylates
ADP
24) What membrane-surface molecules are thought to be most important as cells recognize each
other? A) phospholipids B) integral proteins C) peripheral proteins D) cholesterol E)
glycoproteins
25) 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) maintaining fluidity of the phospholipid bilayer D) attaching
to the cytoskeleton E) establishing the diffusion barrier to charged molecules
26) Which of the following adheres to the extracellular surface of animal cell plasma
membranes? A) fibers of the extracellular matrix B) fibers of the cytoskeleton C) the
phospholipid bilayer D) cholesterol E) carrier proteins
27) What kinds of molecules pass through a cell membrane most easily? A) large and
hydrophobic B) small and hydrophobic C) large polar D) ionic E) monosaccharides such as
glucose
28) Which of the following is a characteristic feature of a carrier protein in a plasma membrane?
A) It is a peripheral membrane protein. B) It exhibits a specificity for a particular type of
molecule. C) It requires the expenditure of cellular energy to function. D) It works against
diffusion. E) It has few, if any, hydrophobic amino acids.
29) After a membrane freezes and then thaws, it often becomes leaky to solutes. The most
reasonable explanation for this is that A) transport proteins become nonfunctional during
freezing. B) the lipid bilayer loses its fluidity when it freezes. C) aquaporins can no longer
function after freezing. D) the integrity of the lipid bilayer is broken when the membrane freezes.
E) the solubility of most solutes in the cytoplasm decreases on freezing.
30) 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+ E) starch
31) The selective permeability of biological membranes is dependent on which of the following?
A) the type of transport proteins that are present in the membrane B) the lipid bilayer being
permeable to primarily small, nonpolar molecules C) the types of carbohydrates on the surface of
the membrane D) A and B only E) A, B, and C
32) Which of the following statements is correct about diffusion? A) It is very rapid over long
distances. B) It requires an expenditure of energy by the cell. C) It is a passive process in which
molecules move from a region of higher concentration to a region of lower concentration. D) It is
an active process in which molecules move from a region of lower concentration to one of higher
concentration. E) It requires integral proteins in the cell membrane.
33) Water passes quickly through cell membranes because A) the bilayer is hydrophilic. B) it
moves through hydrophobic channels. C) water movement is tied to ATP hydrolysis. D) it is a
small, polar, charged molecule. E) it moves through aquaporins in the membrane
Use the diagram of the U-tube in Figure 7.2 to answer the questions that follow. 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.
Figure 7.2
34) Initially, in terms of tonicity, the solution in side A with respect to that in side B is A)
hypotonic. B) plasmolyzed. C) isotonic. D) saturated. E) hypertonic.
35) After the system reaches equilibrium, what changes are observed? A) The molarity of sucrose
and glucose are equal on both sides. B) The molarity of glucose is higher in side A than in side B.
C) The water level is higher in side A than in side B. D) The water level is unchanged. E) The
water level is higher in side B than in side A.
36) A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body
fluids, distilled water, equal to the volume of blood lost, is transferred directly into one of his
veins. What will be the most probable result of this transfusion? A) It will have no unfavorable
effect as long as the water is free of viruses and bacteria. B) The patient's red blood cells will
shrivel up because the blood fluid is hypotonic compared to the cells. C) The patient's red blood
cells will swell because the blood fluid is hypotonic compared to the cells. D) The patient's red
blood cells will shrivel up because the blood fluid is hypertonic compared to the cells. E) The
patient's red blood cells will burst because the blood fluid is hypertonic compared to the cells.
37) Celery stalks that are immersed in fresh water for several hours become stiff and hard.
Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells
of the celery stalks are A) hypotonic to both fresh water and the salt solution. B) hypertonic to
both fresh water and the salt solution. C) hypertonic to fresh water but hypotonic to the salt
solution. D) hypotonic to fresh water but hypertonic to the salt solution. E) isotonic with fresh
water but hypotonic to the salt solution.
38) A cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a test tube of
water containing 0.02 molar glucose. Assuming that glucose is not actively transported into the
cell, which of the following terms describes the tonicity of the external solution relative to the
cytoplasm of the cell? A) isotonic B) hypertonic C) hypotonic D) flaccid E) turgid
Refer to Figure 7.3 to answer the following questions. 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. Figure 7.3
39) 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 isotonic to side B. D) side A is hypertonic to side B with respect to
glucose. E) side A is hypotonic to side B with respect to sodium chloride.
40) If you examine side A after 3 days, you should find A) a decrease the in concentration of
NaCl and glucose and an increase in the water level. B) a decrease in the concentration NaCl,
an of increase in water level, and no change in the concentration of glucose. C) no net change in the
system. D) a decrease in the concentration of NaCl and a decrease in the water level. E) no
change in the concentration of NaCl and glucose and an increase in the water level.
41) Which of the following statements correctly describes the normal tonicity conditions for
typical plant and animal cells? A) The animal cell is in a hypotonic solution, and the plant cell is
in an isotonic solution. B) The animal cell is in an isotonic solution, and the plant cell is in a
hypertonic solution. C) The animal cell is in a hypertonic solution, and the plant cell is in an
isotonic solution. D) The animal cell is in an isotonic solution, and the plant cell is in a hypotonic
solution. E) The animal cell is in a hypertonic solution, and the plant cell is in a hypotonic
solution.
Comprehension Read the following information and refer to Figure 7.4 to answer the following
questions. Five dialysis bags, constructed from a semi-permeable membrane that is 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. Figure 7.4
42) Which line represents the bag that contained a solution isotonic to the 0.6 molar solution at
the beginning of the experiment? Answer: C
43) Which line represents the bag with the highest initial concentration of sucrose? Answer: A
44) Which line or lines represent(s) bags that contain a solution that is hypertonic at the end of
60 minutes? A) A and B B) B C) C D) D E) D and E
45) What is (are) the best explanation(s) for the shape of line E after 50 minutes? A) The bag is
isotonic with the solution around it. B) Water is entering and leaving the bag at the same rate. C)
Sucrose is entering and leaving the bag at the same rate. D) A and B only E) A, B, and C
46) You are working on a team that is designing a new drug. In order for this drug to work, it
must enter the cytoplasm of specific target cells. Which of the following would not be a factor
that determines whether the molecule enters the cell? A) size of the drug molecule B) polarity of
the drug molecule C) charge on the drug molecule D) similarity of the drug molecule to other
molecules transported by the target cells E) lipid composition of the target cells' plasma
membrane
47) All of the following membrane activities require energy from ATP hydrolysis except A)
facilitated diffusion. B) active transport. C) Na+ ions moving out of the cell. D) proton pumps.
E) translocation of potassium into a cell.
48) What are the membrane structures that function in active transport? A) peripheral proteins B)
carbohydrates C) cholesterol D) cytoskeleton filaments E) integral proteins
49) The movement of a substance across a biological membrane against its concentration
gradient with the help of energy input is A) diffusion. B) active transport. C) osmosis. D)
facilitated diffusion. E) exocytosis.
50) Carrier molecules in the membrane and metabolic energy are required for A) osmosis. B)
facilitated diffusion. C) active transport. D) B and C only E) A, B, and C
51) Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small
intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their
glucose-poor cytoplasm. Using this information, which transport mechanism is most probably
functioning in the intestinal cells? A) simple diffusion B) phagocytosis C) active transport pumps
D) exocytosis E) facilitated diffusion
52) The main difference(s) between facilitated diffusion and active transport is (are) A)
facilitated diffusion moves substances down their concentration gradient and active transport
moves them against their gradient. B) facilitated diffusion does not rely on cellular energy and
active transport does. C) facilitated diffusion uses channel or carrier proteins and active transport
does not. D) A and B only E) A, B, and C
53) What is the voltage across a membrane called? A) water potential B) chemical gradient C)
membrane potential D) osmotic potential E) electrochemical gradient
54) In most cells, there are electrochemical gradients of many ions across the plasma membrane
even though there are usually only one or two electrogenic pumps present in the membrane. The
gradients of the other ions are most likely accounted for by A) cotransport proteins. B) ion
channels. C) carrier proteins. D) B and C only E) A, B, and C
55) The sodium-potassium pump is called an electrogenic pump because it A) pumps equal
quantities of Na+ and K+ across the membrane. B) pumps hydrogen ions out of the cell. C)
contributes to the membrane potential. D) ionizes sodium and potassium atoms. E) is used to
drive the transport of other molecules against a concentration gradient.
56) If a membrane protein in an animal cell is involved in the cotransport of glucose and sodium
ions into the cell, which of the following is most likely not true? A) The sodium ions are moving
down their electrochemical gradient. B) Glucose is entering the cell against its concentration
gradient. C) Sodium ions can move down their electrochemical gradient through the
cotransporter whether or not glucose is present outside the cell. D) The higher sodium ion
concentration outside the cell is the result of an electrogenic pump. E) A substance that blocked
sodium ions from binding to the cotransport protein would also block the transport of glucose.
57) The movement of potassium into an animal cell requires A) low cellular concentrations of
sodium. B) high cellular concentrations of potassium. C) an energy source such as ATP or a
proton gradient. D) a cotransport protein. E) a gradient of protons across the plasma membrane
58) Ions diffuse across membranes down their A) chemical gradients. B) concentration gradients.
C) electrical gradients. D) electrochemical gradients. E) A and B are correct.
59) Which of the following characterizes the sodium-potassium pump? A) Sodium ions are
pumped out of a cell against their gradient. B) Potassium ions are pumped into a cell against their
gradient. C) The pump protein undergoes a conformational change. D) Only A and B are correct.
E) A, B, and C are all correct.
60) What mechanisms do plants use to load sucrose produced by photosynthesis into specialized
cells in the veins of leaves? A) an electrogenic pump B) a proton pump C) a contransport protein
D) A and C only E) A, B, and C
61) The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across
the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what
side of the ER membrane will the ATP binding site be on? A) It will be on the cytoplasmic side
of the ER. B) It will be on the side facing the interior of the ER. C) It could be facing in either
direction because the orientation of proteins is scrambled in the Golgi apparatus. D) It doesn't
matter, because the pump is not active in the ER. E) Not enough information is provided to
answer this question.
62) Which of the following statements about membrane structure and function is false? A)
Diffusion of gases is faster in air than across membranes. B) Diffusion, osmosis, and facilitated
diffusion do not require any direct energy input from the cell. C) The types of proteins that are
exposed on one side of a membrane are nearly identical to those exposed on the other side of the
membrane. D) Voltage across the membrane depends on an unequal distribution of ions across
the plasma membrane. E) Special membrane proteins can cotransport two solutes by coupling
diffusion down a concentration gradient to transport against the concentration gradient
63) All of the following processes take material into cells except 14 A) pinocytosis. B)
endocytosis. C) exocytosis. D) active transport. E) carrier-facilitated diffusion.
64) An organism with a cell wall would have the most difficulty doing which process? A)
diffusion B) osmosis C) active transport D) phagocytosis E) exocytosis
65) The membrane activity most nearly opposite to exocytosis is A) plasmolysis. B) osmosis. C)
facilitated diffusion. D) phagocytosis. E) active transport.
66) White blood cells engulf bacteria through what process? A) exocytosis B) phagocytosis C)
pinocytosis D) osmosis E) receptor-mediated exocytosis
67) What is the cause of familial hypercholesterolemia? 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 E) a general lack of glycolipids in the blood
cell membranes
68) In addition to exporting materials from the cytoplasm of the cell, the process of exocytosis is
also important in A) the production of cell walls by plant cells. B) the increase in the size of
cells. C) maintaining the osmotic balance between the cytoplasm and the cell exterior. D) A and
B only E) A, B, and C
69) The difference between pinocytosis and receptor-mediated endocytosis is that A) pinocytosis
brings only water into the cell, but receptor-mediated endocytosis brings in other molecules as
well. B) pinocytosis increases the surface area of the plasma membrane whereas receptormediated 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 requires cellular energy, but receptor-mediated
endocytosis does not. E) pinocytosis can concentrate substances from the extracellular fluid, but
receptor-mediated endocytosis cannot.
70) The interior of the phospholipid bilayer is A) composed of fatty acids. B) hydrophobic. C)
composed of cholesterol. D) hydrophilic. E) water. Answer: B Topic: Web/CD Activity: Selective
Permeability of Membranes
71) Oxygen crosses a plasma membrane by A) osmosis. B) phagocytosis. C) active transport. D)
pinocytosis. E) passive transport.
72) In a hypotonic solution an animal cell will A) lyse. B) experience turgor. C) neither gain nor
lose water. D) shrivel. E) lose water.
73) Endocytosis moves materials ________ a cell via ________. A) into; facilitated diffusion B)
into; membranous vesicles 16 C) into; a transport protein D) out of; diffusion E) out of;
membranous vesicles
74) Cholesterol enters cells via A) phagocytosis. B) osmosis. C) receptor-mediated endocytosis.
D) exocytosis. E) pinocytosis.
75) In what way do the various membranes of a eukaryotic cell differ? 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) Only certain membranes are
constructed from amphipathic molecules. E) Some membranes have hydrophobic surfaces
exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm. Answer:
B
76) According to the fluid mosaic model of membrane structure, proteins of the membrane are
mostly A) spread in a continuous layer over the inner and outer surfaces of the membrane. B)
confined to the hydrophobic core of the membrane. C) embedded in a lipid bilayer. D) randomly
oriented in the membrane, with no fixed inside-outside polarity. E) free to depart from the fluid
membrane and dissolve in the surrounding solution
77) Which of the following factors would tend to increase membrane fluidity? A) a greater
proportion of unsaturated phospholipids B) a greater proportion of saturated phospholipids C) a
lower temperature D) a relatively high protein content in the membrane E) a greater proportion
of relatively large glycolipids compared to lipids having smaller molecular masses
78) Which of the following processes includes all others? A) osmosis B) diffusion of a solute
across a membrane C) facilitated diffusion D) passive transport E) transport of an ion down its
electrochemical gradient
79) Based on the model of sucrose uptake in Figure 7.19 (in the text), which of the following
experimental treatments would increase the rate of sucrose transport into the cell? A) decreasing
extracellular sucrose concentration 17 B) decreasing extracellular pH C) decreasing cytoplasmic
pH D) adding an inhibitor that blocks the regeneration of ATP E) adding a substance that makes
the membrane more permeable to hydrogen ions