Campbell Biology in Focus, 2e (Urry)
Chapter 5 Membrane Transport and Cell Signaling
5.1 Multiple-Choice Questions
1) The fluid mosaic model of the membrane proposed that membranes
A) consist of a phospholipid bilayer composed of a variety of fatty acids.
B) consist of protein molecules embedded in a fluid bilayer of phospholipids.
C) consist of a single layer of phospholipids and proteins.
D) consist of a phospholipid bilayer between two layers of hydrophilic proteins.
2) Which of the following are localized on the exterior of a phospholipid bilayer?
A) saturated fatty acids
B) unsaturated fatty acids
C) phosphate groups
D) cholesterol
3) The primary structural components of the cell membrane are
A) phospholipids and cellulose.
B) phospholipids and proteins.
C) cholesterol and proteins.
D) proteins and cellulose.
E) glycoproteins and cholesterol.
4) 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) the hydrophobic interactions between the fatty acid tails of the two phospholipid monolayers
are the weakest interactions in the membrane.
D) the carbon-carbon bonds of the phospholipid tails are easily broken.
5) A primary function of cholesterol in the plasma membranes of some animals is to
A) make the membrane more rigid, allowing it to resist pressure from outside the cell.
B) facilitate the removal of hydrogen atoms from saturated phospholipids.
C) facilitate cell-cell interactions by binding to receptors on neighboring cells.
D) enable the membrane to stay fluid more easily when the temperature drops.
6) 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.
7) Which of the following 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 average length of the fatty acid tails in membrane
B) by decreasing the percentage of cholesterol molecules in the membrane
C) by decreasing the number of hydrophobic proteins in the membrane
D) by increasing the percentage of unsaturated phospholipids in the membrane
8) An integral membrane protein would have to be
A) hydrophilic.
B) hydrophobic.
C) amphipathic, with at least one hydrophobic region.
D) exposed to water on only one surface of the membrane.
9) Which of the following tend to lack hydrophobic regions on their surface?
A) transmembrane proteins
B) integral proteins
C) peripheral proteins
D) integrins
E) cholesterol
10) How do unsaturated fatty acids help keep any membrane more fluid at lower temperatures?
A) The double bonds form kinks in the fatty acid tails that prevent adjacent lipids from packing
tightly together.
B) Unsaturated fatty acids have a higher cholesterol content that prevents adjacent lipids from
packing tightly together.
C) Unsaturated fatty acids are more polar than saturated fatty acids.
D) The double bonds result in shorter fatty acid tails and therefore thinner membranes.
11) Which of the following is true of integral membrane proteins?
A) They serve only a structural role in membranes.
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.
12) A primary function of polysaccharides attached to glycoproteins and glycolipids of animal
cell membranes is to
A) facilitate diffusion of active transport of molecules into the cell.
B) mediate cell-to-cell recognition.
C) maintain the integrity of a fluid mosaic membrane.
D) maintain membrane fluidity at low temperatures.
13) A protein that spans the phospholipid bilayer one or more times is
A) a transmembrane protein.
B) a glycoprotein.
C) a peripheral protein.
D) an extracellular matrix protein.
14) The movement of the hydrophobic gas nitrous oxide (N2O) (laughing gas) into a cell is an
example of
A) active transport across the lipid bilayer.
B) facilitated diffusion through the lipid bilayer.
C) diffusion through the lipid bilayer.
D) osmosis through the lipid bilayer.
E) cotransport across the lipid bilayer.
15) The cell membranes of Antarctic ice fish might have which of the following adaptations?
A) a high percentage of very long chain saturated fatty acids
B) no cholesterol
C) a high percentage of unsaturated fatty acids
D) a high percentage of trans fatty acids
16) 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) Phospholipids form hydrogen bonds with water at the membrane surface, which moves the
lipids as water moves.
D) Weak hydrophobic interactions in the interior of the membrane are easily disrupted.
17) Which of the following provides the most likely explanation for why cell membranes are
asymmetrical?
A) Proteins only function on the cytoplasmic side of the cell membrane, which results in
asymmetry across the membrane.
B) Cell-to-cell communication requires different proteins on the surfaces of interacting cells.
C) The molecular composition of the inner and outer layers of the cell membrane is determined
by genes.
D) The two sides of a cell membrane face different environments and carry out different
functions.
18) Which of the following is true for the evolution of cell membranes?
A) The fluid mosaic nature of cell membranes provides for the rapid evolution of cell
membranes.
B) The evolution of cell membranes is driven primarily by the evolution of phospholipids as a
result of natural selection.
C) The evolution of cell membranes is driven primarily by the evolution of glycoproteins and
glycolipids as a result of natural selection.
D) The evolution of cell membranes is driven by the evolution of all membrane components as a
result of natural selection.
19) What kinds of molecules pass through a cell membrane most easily?
A) large hydrophobic
B) small hydrophobic
C) large polar
D) small ionic
E) large and hydrophilic
20) 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 a concentration gradient.
21) Which of the following would diffuse through the lipid bilayer of a plasma membrane most
rapidly?
A) glucose
B) starch
C) O2
D) Na+
E) an amino acid
22) Which of the following would diffuse through the lipid bilayer of a plasma membrane most
slowly, if at all?
A) glucose
B) an amino acid
C) O2
D) CO2
E) water
23) Which of the following statements about diffusion is correct?
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 is a passive process in which molecules move from a region of lower concentration to a
region of higher concentration.
24) 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, nonpolar molecule.
E) it moves through aquaporin channel proteins.
25) Celery stalks that are immersed in fresh water for several hours become turgid (stiff). Celery
stalks left in a 0.15 M salt solution become flaccid (limp). From this we can deduce that
A) the fresh water and the salt solution are both hypertonic to the cells of the celery stalks.
B) the fresh water and the salt solution are both hypotonic to the cells of the celery stalks.
C) the fresh water is hypertonic and the salt solution is hypotonic to the cells of the celery stalks.
D) the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks.
E) the fresh water is isotonic and the salt solution is hypertonic to the cells of the celery stalks.
26) Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent
of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?
A) Water will leave the cells, causing them to shrivel and collapse.
B) NaCl will be exported from the red blood cells by facilitated diffusion.
C) The blood cells will take up water, swell, and eventually burst.
D) NaCl will passively diffuse into the red blood cells.
27) Which of the following statements correctly describes the normal tonicity relationships
between typical plant and animal cells and their respective environments?
A) Animal cells are generally in a hypotonic solution, and plant cells are generally in an isotonic
solution.
B) Animal cells are generally in an isotonic solution, and plant cells are generally in a hypotonic
solution.
C) Animal cells are generally in an isotonic solution, and plant cells are generally in a hypertonic
solution.
D) Animal cell are generally in a hypertonic solution, and plant cells are generally in an isotonic
solution.
E) Animal cells are generally in a hypertonic solution, the plant cells are generally in a hypotonic
solution.
28) Submerging a plant cell in distilled water will result in
A) plasmolysis of the cell.
B) lysis of the cell membrane.
C) bursting of the cell.
D) the cell becoming turgid.
E) the cell becoming flaccid.
29) Submerging a red blood cell in distilled water will result in
A) plasmolysis of the cell.
B) lysis of the cell.
C) the cell becoming turgid.
D) the cell becoming flacid.
30) Submerging a red blood cell in a hypertonic solution will result in
A) plasmolysis of the cell.
B) lysis of the cell.
C) the cell becoming turgid.
D) the cell wall shriveling.
31) 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. Based on this information, which transport mechanism is most likely
responsible for glucose transport in the intestinal cells?
A) simple diffusion
B) phagocytosis
C) active transport pumps
D) facilitated diffusion
32) Which of the following membrane activities requires energy from ATP hydrolysis?
A) facilitated diffusion of chloride ions across the membrane through a chloride channel
B) movement of water into a cell through aquaporins
C) movement of sodium ions from a lower concentration in a mammalian cell to a higher
concentration in the extracellular fluid
D) movement of glucose molecules into a bacterial cell from a medium containing a higher
concentration of glucose than inside the cell
E) movement of carbon dioxide out of a paramecium
33) 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 bind to the same site on the cotransporter.
B) Transport of glucose against its concentration gradient provides energy for uptake of sodium
ions against the electrochemical gradient.
C) Sodium ions can be transported whether or not glucose is present outside the cell, but glucose
transport requires cotransport of sodium ions.
D) Transport of sodium ions down their electrochemical gradient facilitates the transport of
glucose against its concentration gradient.
E) Following transport of sodium ions into the cell, the cotransporter can also transport
potassium ions out of the cell.
34) 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.
E) receptor-mediated endocytosis.
35) What is the voltage across a membrane called?
A) water potential
B) chemical gradient
C) membrane potential
D) osmotic potential
E) electrochemical gradient
36) The sodium-potassium pump is called an electrogenic pump because it
A) pumps electrons across the plasma membrane.
B) pumps hydrogen ions out of the cell.
C) contributes to the membrane potential.
D) ionizes sodium and potassium atoms.
37) Transport of potassium ions into an animal cell by the sodium-potassium pump requires
A) low intracellular concentrations of sodium.
B) high intracellular concentrations of sodium.
C) high intracellular concentrations of potassium.
D) low intracellular concentrations of potassium.
E) energy from ATP.
38) The sodium-potassium pump generates the following concentration gradients across the
plasma membrane:
A) high [Na+] and [K+] inside the cell and low [Na+] and [K+] outside.
B) low [Na+] and [K+] inside the cell and high [Na+] and [K+] outside.
C) low [Na+] and high [K+] inside the cell and high [Na+] and low [K+] outside.
D) high [Na+] and low [K+] inside the cell and low [Na+] and high [K+] outside.
39) Proteins that allow the diffusion of ions across membranes in the direction of their
concentration gradients are most likely
A) channel proteins.
B) carrier proteins.
C) aquaporins.
D) active transport pumps.
40) Which of the following would increase the electrochemical gradient across a membrane?
A) a chloride channel
B) a sucrose-proton cotransporter
C) a proton pump
D) a potassium channel
41) 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 pumps must have evolved before any living organisms were present on Earth.
B) Proton pumps are an essential feature of all cell membranes.
C) Proton gradients across a membrane were used by cells that were the common ancestor of all
three domains of life.
D) Cells of each domain evolved proton pumps independently when oceans became more acidic.
42) A bacterium engulfed by a white blood cell through phagocytosis will be digested by
enzymes contained in
A) peroxisomes.
B) lysosomes.
C) Golgi vesicles.
D) vacuoles.
E) secretory vesicles.
43) Familial hypercholesterolemia is characterized by extremely high levels of cholesterol in the
blood, which results from
A) defective cell membranes that cannot incorporate cholesterol.
B) poor attachment of cholesterol to the extracellular matrix of cells.
C) inhibition of the cholesterol active transport system in red blood cells.
D) nonfunctional or missing LDL receptors on cell membranes.
44) The difference between pinocytosis and receptor-mediated endocytosis is that
A) pinocytosis brings only water molecules into the cell, whereas 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 is highly selective.
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.
45) In receptor-mediated endocytosis, receptor molecules are initially localized on the outer
surface of the plasma membrane. Where do the receptors end up following endocytosis?
A) on the inside surface of the plasma membrane
B) on the inside surface of a vesicle
C) on the outer surface of a vesicle
D) on the outer surface of the nucleus
E) on the inside surface of the Golgi apparatus
46) Which of the following is the first event that occurs following the binding of a ligand by a
membrane receptor protein?
A) An intracellular enzyme is activated by phosphorylation.
B) An intracellular G protein is activated.
C) The membrane receptor protein undergoes a conformational change.
D) The membrane receptor protein enters the cytoplasm.
47) Which of the following is true of steroid receptors?
A) The receptor molecules are themselves lipids or glycolipids.
B) The receptor molecules are transmembrane proteins with the ligand binding domain on the
outside of the cell.
C) The receptor molecules are transmembrane proteins with the ligand binding domain on the
inside of the cell.
D) The receptor molecules are peripheral proteins embedded in the interior layer of the plasma
membrane.
E) The receptor molecules may be soluble proteins in the cytoplasm.
48) Which of the following is the most likely fate of animal cells that lack receptors for local
paracrine signal molecules?
A) They would be unable to grow and divide in response to growth factors from nearby cells.
B) They would be unable to respond to hormone signals delivered through the bloodstream.
C) They would bind locally secreted growth factors, but intracellular signal pathways would be
blocked.
D) They would grow and divide normally.
49) The secretion of a signal molecule by a cell into the local environment, followed by a
response by a number of cells in the immediate vicinity, is an example of
A) hormonal signaling.
B) synaptic signaling.
C) endocrine signaling.
D) paracrine signaling.
E) extracellular matrix signaling.
50) Which of the following characteristics is unique to plant hormones?
A) Plant hormones may be bound by intracellular steroid receptors.
B) Plant hormones may be delivered to target cells through a vascular system.
C) Plant hormones may be delivered to target cells through the air.
D) The target cells for plant hormones may be located large distances from the cells that produce
and secrete the hormones.
51) When a neuron responds to a particular neurotransmitter by opening gated ion channels, the
neurotransmitter is serving as which part of the signal pathway?
A) receptor
B) relay molecule
C) signal molecule
D) transducer
E) molecule protein
52) The mechanism by which testosterone alters cell function is by
A) binding to a receptor protein that enters the nucleus and activates specific genes.
B) serving as a transmembrane signal receptor that activates cell-signaling pathways.
C) acting as a steroid signal receptor that activates ion channel proteins.
D) serving as a second messenger that activates cell-signaling pathways.
53) The primary function of transcription factors is
A) to regulate the conversion of ATP into cAMP.
B) to regulate DNA synthesis.
C) to regulate gene expression.
D) to transmit signals from an activated receptor to intracellular G proteins.
54) In general, a signal transmitted via a phosphorylation cascade
A) is initiated by a phosphorylase enzyme.
B) is propagated by a steroid receptor.
C) results in a conformational change in each phosphorylated protein.
D) is turned off by a kinase enzyme.
55) Approximately what proportion of human genes are thought to encode protein kinases?
A) 0.01%
B) 0.5%
C) 2%
D) 10%
56) Immediately following binding of a growth factor, an activated receptor would most likely
stimulate
A) activation of a protein kinase.
B) activation of adenylyl cyclase.
C) activation of a calcium-binding protein.
D) activation of a protein phosphatase.
57) Following activation of a receptor, which sequence below represents the correct order in
which components will be involved in a signaling pathway that utilizes the second messenger
cAMP?
A) G protein → cAMP → adenyl cyclase → protein kinase
B) G protein → adenyl cyclase → cAMP → protein kinase
C) adenyl cyclase → cAMP → G protein → protein kinase
D) cAMP → adenyl cyclase → protein kinase → G protein
E) protein kinase → G protein → adenyl cyclase → cAMP