Deck 8: Cell Membranes

Question 1

Which of the following types of molecules are most likely to lack hydrophilic domains?

A) transmembrane proteins
B) ion transport proteins
C) peripheral membrane proteins
D) cholesterol

Answer 1

D

Question 2

Which component in the figure above represents a microfilament of the cytoskeleton?

A) A
B) B
C) C
D) D

Answer 2

C

Question 3

Which of the following statements best describes how unsaturated fatty acids increase membrane fluidity 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, which prevents adjacent lipids from packing tightly.
C) Unsaturated fatty acids are more nonpolar than saturated fatty acids.
D) The double bonds block interaction among the hydrophilic head groups of the lipids.

Answer 3

A

Question 4

Cell membranes have distinct inside and outside faces. Which of the following statements is the most plausible explanation for the asymmetrical nature of the two layers of the membrane?

A) Cell membranes form a border between adjacent cells in tightly packed tissues such as epithelium.
B) Cell membranes communicate signals between different cell types.
C) The two layers of a cell membrane face different environments and carry out different functions.
D) Proteins only function on the cytoplasmic side of the cell membrane.

Question 5

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on 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) Permeability will decrease initially then increase as the bilayer fills with glucose.

Question 6

Which component in the accompanying figure plays a critical role in cell-cell recognition?

A) A
B) B
C) C
D) E

Question 7

Which of the following statements best describes a characteristic of biological membranes?

A) Phospholipids move laterally within the plane of the membrane.
B) Phospholipids frequently flip-flop from one layer of the membrane to the other.
C) Phospholipids generally occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.
D) Phospholipids are arranged with hydrophilic tails in the interior of the membrane.

Question 8

Which of the following statements best describes a characteristic feature of integral membrane proteins?

A) They are hydrophilic.
B) They are hydrophobic.
C) They are amphipathic, with at least one hydrophobic region.
D) They are localized to the interior surface of the membrane.

Question 9

Which of the following statements best explains how the membranes in winter wheat are able to remain fluid in extremely cold temperatures?

A) The membranes contain an increased proportion of unsaturated phospholipids.
B) The membranes contain a reduced proportion of cholesterol molecules.
C) The membranes contain a reduced proportion of hydrophobic proteins.
D) The membranes contain an increased proportion of glycolipids.

Question 10

In which of the following ways 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.

Question 11

Which component in the figure above represents a protein fiber of the extracellular matrix?

A) A
B) B
C) C
D) E

Question 12

Which component in the figure above is hydrophilic?

A) A
B) B
C) C
D) D

Question 13

Which component in the figure above represents cholesterol?

A) B
B) C
C) D
D) E

Question 14

Which of the following statements best describes the structure of a membrane based on the fluid mosaic model?

A) The membrane is composed of a fluid bilayer of phospholipids between two layers of hydrophilic proteins.
B) The membrane is composed of a single layer of fluid phospholipids between two layers of hydrophilic proteins.
C) The membrane is composed of a mosaic of fluid polysaccharides and amphipathic proteins.
D) The membrane is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins.

Question 15

Which of the following types of molecules are most likely to be excluded from the hydrophobic portion of the phospholipid bilayer?

A) transmembrane proteins
B) integral membrane proteins
C) peripheral membrane proteins
D) cholesterol

Question 16

An animal cell that lacks carbohydrates on the external surface of its plasma membrane would likely be impaired in which of the following functions?

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

Question 17

Which of the following types of molecules are least likely to diffuse through the phospholipid bilayer of a cell membrane?

A) large hydrophobic molecules
B) small hydrophobic molecules
C) carbon dioxide
D) small ions

Question 18

Which of the following statements best explains the reason that lipids and proteins are 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.

Question 19

Which of the following types of molecules will diffuse through a cell membrane most readily?

A) large hydrophobic molecules
B) small hydrophobic molecules
C) large polar molecules
D) small ionic molecules

Question 20

Which of the following statements best describes a characteristic feature of a carrier protein in a plasma membrane?

A) It exhibits specificity for a particular type of molecule.
B) It requires the expenditure of cellular energy to function.
C) It works against a concentration gradient.
D) It has no hydrophobic regions.

Question 21

When the interior of a cell is in equilibrium with its environment, which of the following statements best describes the relative movement of molecules that can diffuse through the plasma membrane?

A) There is directed movement of molecules into or out of the cell.
B) There is random movement of molecules into and out of the cell.
C) There is no movement of molecules into or out of the cell.
D) All movement of molecules across the plasma membrane occurs by active transport.

Question 22

What will happen to a red blood cell (RBC), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water?

A) The cell will shrink because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.
B) The cell will shrink because the water in the beaker is hypertonic relative to the cytoplasm of the RBC.
C) The cell will 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.

Question 23

Five dialysis bags, constructed of a type of membrane that 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 weighed, and the percent change in mass of each bag was graphed. 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

Question 24

Which of the following cellular processes includes all of the others?

A) osmosis
B) facilitated diffusion
C) passive transport
D) transport of an ion down its electrochemical gradient

Question 25

Which of the following results is most likely when a plant cell is submerged in a hypertonic solution?

A) The cell will burst.
B) Plasmolysis will shrink the interior of the cell.
C) The cell will become flaccid.
D) The cell will become turgid.

Question 26

The solutions in the two arms of a 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. Which of the following statements best describes the relationship between the solutions on both sides of the U-tube?

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 more turgid than side B

Question 27

In which of the following circumstances would the cell or organism have 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

Question 28

Which of the following statements best describes a characteristic feature of osmosis?

A) Osmosis only takes place in red blood cells.
B) The process of osmosis requires energy from ATP hydrolysis.
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.

Question 29

Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown solution (1-6) 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. Cubes of sweet potato (1 cm3) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. From the data provided, which unknown solution has a molarity that most closely reflects the molarity of sweet potato cells?

A) 2
B) 3
C) 4
D) 5

Question 30

Which of the following statements best describes the normal tonicity conditions for typical plant and animal cells in their native environments?

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.

Question 31

Which of the following statements best describes a characteristic feature of diffusion?

A) It is very rapid over long distances.
B) It requires an expenditure of energy by the cell.
C) It is an active process in which molecules move from a region of lower concentration to a region of higher concentration.
D) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

Question 32

Five dialysis bags, constructed of a type of membrane that 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 weighed, and the percent change in mass of each bag was graphed. Which line in the graph represents the bag with the highest initial concentration of sucrose?

A) A
B) B
C) C
D) D

Question 33

A new drug designed for the treatment of lung cancer must specifically enter the cytoplasm of lung cells while not entering the cells of other tissues. Which of the following characteristics would likely enhance the specificity of this drug?

A) the relative hydrophobicity of the drug molecule
B) the phospholipid composition of lung cell membranes
C) the specificity of the drug molecule for binding to the extracellular matrix of lung cells
D) the similarity of the drug molecule to other molecules normally transported lung cells

Question 34

A defect in which of the following molecules would dramatically reduce the rate of diffusion of water across cell membranes?

A) sodium-potassium pump
B) aquaporins
C) gated ion channels
D) ATP

Question 35

The solutions in the two arms of a 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. Which of the following is the most likely result when the system has reached equilibrium?

A) The concentration of sucrose on side A will be greater than the concentration of sucrose on side B.
B) The water level will be higher in side A than in side B.
C) The water levels will be unchanged.
D) The water level will be higher in side B than in side A.

Question 36

Which of the following results is most likely result if a portion of an animal's blood is replaced with distilled water?

A) The animal's red blood cells will shrivel up because the blood has become hypotonic compared to the cells.
B) The animal's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells.
C) The animal's red blood cells will shrivel up because the blood has become hypertonic compared to the cells.
D) The animal's red blood cells will burst because the blood has become hypertonic compared to the cells.

Question 37

The solutions in the two arms of a 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. When the system illustrated above reaches equilibrium, the sugar concentrations on both sides of the U-tube will be ________.

A) 2 M sucrose, 1 M glucose
B) 1 M sucrose, 2 M glucose
C) 1 M sucrose, 1 M glucose
D) 1.5 M sucrose, 1.5 M glucose

Question 38

Celery stalks that are immersed in fresh water for several hours become stiff. Which of the following statements best explains the observation that similar stalks left in a 0.15 M salt solution become limp?

A) The fresh water and the salt solution are both hypertonic to the cells of the celery stalks.
B) The fresh water is hypotonic and the salt solution is hypertonic 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 isotonic and the salt solution is hypertonic to the cells of the celery stalks

Question 39

Five dialysis bags, constructed of a type of membrane that 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 weighed, and the percent change in mass of each bag was graphed. Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic to the solution in the beaker at 50 minutes?

A) A and B
B) B
C) D
D) D and E

Question 40

Which of the following molecules would likely diffuse through the lipid bilayer of a plasma membrane most rapidly?

A) sucrose
B) an amino acid
C) O₂
D) Na+

Question 41

In receptor-mediated endocytosis, membrane receptors bind to molecules outside of the cell. Immediately following endocytosis where will the membrane receptors be located?

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

Question 42

Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown solution (1-6) 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. Cubes of sweet potato (1 cm3) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. From the data given, which statement below most accurately describes something that has occurred in response to a particular unknown solution?

A) Unknown solution 5 contains the highest concentration of sucrose, and the change in mass is due to the active transport of sucrose out of the cell.
B) Osmosis of water molecules from unknown solution 2 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 6.
D) Unknown solution 3 represents a sucrose concentration slightly higher than the molarity of sweet potato cells, thus water is transported out of the cells.

Question 43

Which of the following molecules would decrease the electrochemical gradient across a membrane?

A) an aquaporin
B) a proton pump
C) a potassium channel
D) a sucrose carrier protein

Question 44

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 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

Question 45

Which of the following statements best explains the observation that proton pumps are used by organisms in every domain of life?

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.

Question 46

Which of the following statements best describes the difference between pinocytosis and receptor-mediated endocytosis?

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

Question 47

Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown solution (1-6) 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. Cubes of sweet potato (1 cm3) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions.

Which unknown solution contains the highest concentration of sucrose?

A) 1
B) 3
C) 4
D) 5

Question 48

The voltage across a membrane is called the ________.

A) chemical gradient
B) membrane potential
C) osmotic potential
D) electrochemical gradient

Question 49

Which of the following factors is a primary contributor underlying 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

Question 50

In some cells, there are many different ion electrochemical gradients across the plasma membrane even though there are usually only one or two types of proton pumps present in the membrane. The gradients of the other ions are most likely established by which of the following?

A) cotransport proteins
B) ion channels
C) pores in the plasma membrane
D) passive diffusion across the plasma membrane

Question 51

Which of the following statements most accurately compares primary factors responsible for simple diffusion versus active transport?

A) Simple diffusion is driven by a concentration gradient, while active transport is driven by ADP.
B) Simple diffusion is driven by a concentration gradient, while active transport is driven by ATP hydrolysis.
C) Simple diffusion is driven by ATP hydrolysis, while active transport is driven by an electrochemical gradient.
D) Simple diffusion is driven transmembrane pumps, while active transport is driven by ATP hydrolysis.

Question 52

Which of the following statements best describes some aspect of the function 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.

Question 53

The force driving simple diffusion is ________, while the energy source for active transport is ________.

A) a concentration gradient; ADP
B) a concentration gradient; ATP hydrolysis
C) transmembrane pumps; an electrochemical gradient
D) phosphorylated carrier proteins; ATP

Question 54

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. Because phosphate import depends on a pH gradient across the membrane, phosphate transport is most likely an example of which of the following transport processes?

A) passive diffusion
B) facilitated diffusion
C) active transport
D) cotransport

Question 55

Which of the following processes is used by white blood cells when engulfing bacteria?

A) phagocytosis
B) pinocytosis
C) osmosis
D) receptor-mediated exocytosis

Question 56

Diffusion of ions across membranes through specific ion channels is driven by ________.

A) active transport pumps
B) ion concentration gradients only
C) electrical gradients only
D) ion electrochemical gradients

Question 57

An organism with a cell wall would most likely be unable to take in materials through which of the following processes?

A) osmosis
B) active transport
C) phagocytosis
D) facilitated diffusion

Question 58

Which of the following statements best describes characteristic activities of a sodium-potassium pump?

A) The pump moves three potassium ions out of a cell and two sodium ions into a cell while producing ATP for each cycle.
B) The pump moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis.
C) The pump moves three potassium ions out of a cell and two sodium ions into a cell using energy from ATP hydrolysis.
D) The pump moves three sodium ions out of a cell and two potassium ions into a cell and generates an ATP in each cycle.

Question 59

Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to diarrhea. Today these diseases are usually not fatal because of the development of which of the following types of treatments?

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 salt and glucose

Question 60

Which of the following statements best explains why the sodium-potassium pump is an electrogenic pump?

A) It transports equal quantities of Na+ and K+ across the membrane in opposite directions.
B) It is used to drive the transport of glucose against a concentration gradient.
C) It decreases the voltage difference across the membrane.
D) It generates voltage across the membrane.

Question 61

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. What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV enters the cell by endocytosis 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.

Question 62

Which of the following organelles plays a primary role in the digestion of bacteria engulfed by white blood cells?

A) lysosomes
B) Golgi vesicles
C) vacuoles
D) secretory vesicles

Question 63

Based on the below figure, which of these experimental treatments would increase the rate of sucrose transport into a plant cell?

A) decreasing extracellular sucrose concentration
B) decreasing extracellular pH
C) decreasing cytoplasmic pH
D) adding a substance that makes the membrane more permeable to hydrogen ions

Question 64

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

Question 65

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) Only certain membranes are constructed from amphipathic molecules.

Question 66

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 interior of the membrane
C) embedded in a lipid bilayer
D) randomly oriented in the membrane, with no fixed inside-outside polarity

Question 67

Which of the following processes includes all the others?

A) osmosis
B) diffusion of a solute across a membrane
C) passive transport
D) transport of an ion down its electrochemical gradient