Deck 6: Cell Membranes

Question 1

In a biological membrane, the phospholipids are arranged in a _______, with the _______.

A) bilayer; fatty acid tails pointing toward each other
B) bilayer; fatty acid tails facing outward
C) single layer; fatty acid tails facing the interior of the cell
D) single layer; phosphorus-containing region facing the interior of the cell
E) bilayer; phosphorus groups in the interior of the membrane

Answer 1

A

Question 2

Refer to the figure below showing results from an analysis of the fluidity of neutrophil membranes as a function of their cholesterol content.Neutrophils are a type of white blood cell in humans. Which statement is consistent with these data?

A) Cholesterol has a negligible influence on cell membrane fluidity.
B) The greater the cholesterol content in a membrane, the more fluid the membrane is.
C) A membrane with less cholesterol is more fluid than a membrane with more cholesterol.
D) Membrane fluidity increases with increasing cholesterol concentration.
E) There is an inverse relationship between membrane fluidity and cholesterol content.

Answer 2

C

Question 3

One student mentioned to another that the fluidity of a cell membrane can be changed by changing the membrane's lipid composition.The second student expressed doubt about this claim.What evidence could the first student find in a research journal to support his claim?

A) A comparison of lipid compositions of membranes in different cells within the same organism
B) An analysis of the change in fatty acid compositions of liver cell membranes in juvenile fish as they mature into adults
C) Results from cell fusion experiments between the same two cells that measure diffusion rates of different membrane proteins
D) Measurement of diffusion rates of the same protein in cell membranes containing different percentages of saturated and unsaturated fatty acids
E) An analysis of the saturated and unsaturated fatty acid content in membranes of skin cells from a single population of cane toads

Answer 3

D

Question 4

Refer to the figure below. Which statement about the lipid bilayer shown in the figure is false?

A) The area labeled A contains hydrophilic portions of fatty acids.
B) The area labeled A contains polar groups that can interact with water.
C) The area labeled B contains hydrophobic regions of fatty acids.
D) The area labeled B allows for the movement of charged particles.
E) The area labeled B allows for the diffusion of lipid-soluble particles.

Question 5

The hydrophilic regions of a membrane protein would most likely be found

A) only in cell membranes.
B) associated with the fatty acid region of the lipids.
C) in the interior of the membrane.
D) exposed on the surface of the membrane.
E) either on the surface or inserted into the interior of the membrane.

Question 6

The plasma membrane of the bacterium Pseudomonas syringae is able to remain fluid when it is extremely cold.The bacterium most likely accomplishes this by

A) increasing the number of cholesterol molecules present.
B) closing protein channels.
C) decreasing the number of hydrophobic proteins present.
D) replacing saturated fatty acids with unsaturated fatty acids.
E) using fatty acids with longer tails.

Question 7

Ion channels are formed by a particular kind of membrane protein that allows the passage of a specific ion under certain conditions.This type of protein is most likely a(n)

A) peripheral protein with additional hydrophobic domains.
B) integral protein with a transmembrane domain.
C) phospholipid with hydrophilic domains.
D) enzyme with an asymmetrical arrangement on either side of the plasma membrane.
E) membrane protein that is able to move freely within the phospholipid bilayer.

Question 8

If a cell membrane lacking integral proteins is prepared by the freeze-fracture technique and examined under the electron microscope, the exposed interior of the membrane bilayer will

A) reveal a bumpy surface.
B) show hydrophobic side chains.
C) show an asymmetric distribution of proteins.
D) show cytoskeletal anchors.
E) look smooth.

Question 9

Experimental results from five different studies on cell membranes are given.Which results could be used as evidence to support the claim that temperature affects a membrane's fluidity?

A) Results from freeze-fracture imaging of cell membranes isolated from blood cells of Arctic and desert rabbits
B) A comparison of diffusion rates of different membrane proteins at 37°C in the cell membranes of liver cells from mice
C) A chemical analysis of the saturated and unsaturated fatty acid content in membranes of intestinal cells from a single population of tropical frogs
D) A comparison of lipid compositions of membranes in different cells within the same organism
E) An analysis of the change in fatty acid compositions of liver cell membranes in a fish species before and after they migrate from warm to cold waters

Question 10

Membrane proteins are asymmetrically distributed according to the function of the membrane and its lipid composition.Which statement about peripheral membrane proteins is true?

A) They do not contain any hydrophilic regions.
B) They are embedded in the phospholipid bilayer.
C) They are able to move freely within the plasma membrane.
D) Their charged regions interact with other proteins or with phospholipids.
E) Their hydrophobic side chains interact with the lipid bilayer.

Question 11

The LDL receptor is an integral membrane protein that extends both outside and into the interior of the cell.The amino acid side chains (R groups) in the region of the protein that crosses the membrane are most likely

A) polar.
B) hydrophilic.
C) hydrophobic.
D) carbohydrates.
E) lipids.

Question 12

Which observation can be used as evidence that the cell membrane has a fluid nature?

A) In the laboratory, two cells from different species can be fused together to make one large cell.
B) Images obtained using freeze-fracture electron microscopy reveal that the membrane contains embedded proteins.
C) Chemical analysis reveals that cell membranes contain phospholipids, proteins, and cholesterol as major components.
D) Analysis of the amino acids present in protein regions embedded in cell membranes show that they mainly have hydrophobic side chains.
E) The cholesterol content in cell membranes varies depending on cell type, and it is generally higher than in organelle membranes.

Question 13

The compounds in a biological membrane that form a barrier to the movement of hydrophilic materials across the membrane are

A) integral membrane proteins.
B) carbohydrates.
C) lipids.
D) nucleic acids.
E) peripheral membrane proteins.

Question 14

The membrane components that enable a biological membrane to have fluidity are

A) integral membrane proteins.
B) carbohydrates.
C) oligosaccharides.
D) peripheral membrane proteins.
E) lipids.

Question 15

A biologist wants to compare the fluidity of membranes from different human cells.Which data will provide information that can be used for this analysis?

A) Integral membrane protein and peripheral membrane protein content
B) Cholesterol content and phospholipid fatty acid composition and content
C) Mass percentage of membrane proteins and mass percentage of lipids
D) Integral membrane protein densities in different locations of a membrane
E) Glycolipid and glycoprotein content and distribution in a membrane

Question 16

Protein movement within a membrane may be restricted by

A) glycolipids and glycoproteins.
B) cell fusion.
C) the cytoskeleton.
D) cell adhesion.
E) peripheral membrane proteins.

Question 17

Refer to the table below. According to the data presented in the table, biological membranes differ in composition because of differences in

A) gene expression.
B) anatomical location.
C) lipid arrangement.
D) biological origin.
E) biological function.

Question 18

How do the cell membranes of a hibernating animal change in colder temperatures?

A) Cholesterol content is increased.
B) Saturated fatty acids are more tightly packed.
C) Integral membrane proteins increase in number.
D) Unsaturated fatty acids make up more of the lipid composition.
E) Fatty acids with longer tails increase in number.

Question 19

Which membrane protein type would likely be removed most easily from a cell membrane in a laboratory experiment?

A) Integral proteins
B) Channel proteins
C) Peripheral proteins
D) Transmembrane proteins
E) Gated channels

Question 20

If the hydrophilic side chains of a transmembrane protein were removed, the protein would most likely

A) remain within the phospholipid bilayer.
B) extend farther into the cytoplasm.
C) protrude into the extracellular space.
D) remain anchored to the cytoskeleton.
E) become a peripheral protein.

Question 21

Refer to the figure below. The type of cell junction shown is most efficient in

A) animal cells that require a tight structure.
B) animal cells that conduct electrical activity, as in the heart.
C) muscles, where rapid reflexes are required.
D) epithelial cells that line animal body cavities.
E) skin cells that receive stress.

Question 22

Scientists have been able to engineer young laboratory mice to have a defective gene for a particular integrin protein only in epidermal skin cells.These mice develop into adults with severe hair loss and skin blistering.Which statement explains the connection between the mutation and the observed physical problems of the mice?

A) A membrane protein receptor is absent, causing loss of cell signaling.
B) The mice cannot produce any extracellular matrix proteins.
C) Cell-cell communication is lost because of a lost cell junction.
D) Epidermal cells cannot express their genes properly.
E) Epidermal cells cannot connect to the extracellular matrix.

Question 23

Cell adhesion occurs through the interactions of

A) glycoproteins and glycolipids.
B) cholesterol and fatty acids.
C) phospholipids and glycerol.
D) oligosaccharides and oligonucleotides.
E) integral proteins and cholesterol.

Question 24

Which type of molecule can function as a recognition signal for interactions between cells?

A) RNA
B) Phospholipids
C) Cholesterol
D) Fatty acids
E) Glycolipids

Question 25

Integrin on the cell surface of a white blood cell binds reversibly with the extracellular matrix of blood vessel walls.This reversibility allows for

A) communication between cells.
B) homotypic binding.
C) heterotypic movement.
D) cell movement.
E) passage of dissolved materials.

Question 26

Refer to the figure below. The type of cell junction shown is most efficient in

A) animal cells that must exchange a lot of material with adjacent cells.
B) animal cells that conduct electrical activity, as in the heart.
C) muscles, where rapid reflexes are required.
D) epithelial cells that line animal body cavities.
E) skin cells that receive stress.

Question 27

Heart muscle cells beat in unison because of the rapid spread of electrical current through

A) tight junctions.
B) desmosomes.
C) gap junctions.
D) integral membrane proteins.
E) neurons.

Question 28

You are monitoring the diffusion of a molecule across a membrane.Of the options listed below, the fastest rate of diffusion would result from an internal concentration of _______ $\mu$ M and an external concentration of _______ $\mu$ M.

A) 5; 60
B) 35; 40
C) 50; 40
D) 50; 50
E) 100; 120

Question 29

You are working in a lab that is studying cell recognition and cell attachment in a red sponge.You need to culture individual cells in a medium that promotes cell recognition and attachment of isolated cells.Which of the following would you add to the culture medium?

A) Cellulose beads
B) Glycolipids
C) Glycoproteins from a different species of sponge
D) A species-specific polysaccharide
E) Complementary binding surfaces

Question 30

Osmosis is a specific form of

A) diffusion.
B) facilitated transport.
C) active transport.
D) secondary active transport.
E) movement of water by carrier proteins.

Question 31

Two membrane components that serve as cell recognition sites are

A) peripheral and integral membrane proteins.
B) hydrophilic and hydrophobic domains.
C) carbohydrates and proteins.
D) glycolipids and glycoproteins.
E) amino acids and lipids.

Question 32

Sponges are multicellular organisms whose bodies allow water to circulate freely.If isolated cells from one species were added to a solution of isolated cells from another species, what would you expect in terms of binding among the cells?

A) Cells from both species would bind to one another.
B) Cells from one species would bind only to others of the same species.
C) Cell binding would occur according to which type of cell was present in greater numbers.
D) The cells would bind according to size, with no difference in species.
E) The cells would remain isolated without binding between any groups.

Question 33

A student claims that cell recognition and cell adhesion refer to the same function.Which statement best evaluates this claim?

A) This statement is accurate, because cell recognition and cell adhesion rely on the ability of molecules from different cells to have complementary surfaces.
B) This statement is accurate, because cell recognition and cell adhesion are both abolished if molecules on different cells are prevented from interacting.
C) This statement is not accurate, because cell recognition is the basis for cell adhesion, as well as for many other functions.
D) This statement is not accurate, because cell adhesion is the basis for cell recognition as well as for many other functions.
E) This statement is not accurate, because cell recognition and cell adhesion have no overlap in function.

Question 34

In animal cell junctions, _______ seal intercellular spaces, _______ reinforce attachments, and _______ allow for communication between cells.

A) keratins; desmosomes; connexins
B) tight junctions; desmosomes; gap junctions
C) cell recognition molecules; adhesion molecules; tight junctions
D) junction proteins; adhesion molecules; connexins
E) desmosomes; gap junctions; tight junctions

Question 35

A group of transmembrane proteins involved in maintaining animal cell structure via their interactions with the cytoskeleton are known as

A) integrins.
B) desmosomes.
C) seal tissues.
D) connexins.
E) keratins.

Question 36

You are studying the effects of different substances on frog heart muscle cells.You treat the cells with a substance that blocks gap junctions.What do you expect will occur?

A) The cells will not be able to maintain their structure.
B) The gap junctions will not be able to provide stability.
C) The electric current will not spread evenly to adjacent heart cells.
D) Nutrients will not pass between the cells.
E) Nerve impulses will not be transmitted to the cells.

Question 37

If tight junctions were replaced by desmosomes in cells lining the bladder,

A) dissolved substances would move freely through the extracellular matrix.
B) membrane protein migration would be restricted.
C) intercellular spaces would be sealed off.
D) the number of gap junctions would increase.
E) pressure on the desmosomes would increase.

Question 38

Which factor does not affect the rate of diffusion of a substance?

A) Temperature of the solution
B) Concentration gradient
C) Density of the solution
D) Presence of other solutes in the solution
E) Molecular diameter of the diffusing material

Question 39

Which is the name of a specialized cell junction that allows rapid spread of electric current via the flow of ions between animal cells?

A) Gap junction
B) Tight junction
C) Desmosome
D) Connexin
E) Integrin

Question 40

A biologist hypothesizes that a particular membrane protein is distributed throughout the cell and anchored to the cytoskeleton.Which experimental technique could provide evidence to test the biologist's hypothesis, and why?

A) Freeze-fracturing techniques, because they can be used to identify cell locations of membrane proteins
B) Freeze-fracturing techniques, because they can distinguish between integral and peripheral proteins
C) Cell fusion techniques, because they can be used to analyze the diffusion rate of a membrane protein
D) Cell fusion techniques, because they can be used to determine the fluidity of a membrane
E) Cell fusion techniques, because they can distinguish between membrane proteins of different sizes by their diffusion rates

Question 41

If a hospital patient is mistakenly administered pure water instead of a saline solution that is isotonic to blood during intravenous (IV) therapy, the patient's red blood cells will

A) shrink and collapse.
B) release water to the plasma along its concentration gradient.
C) absorb water from the plasma and eventually burst.
D) allow water to move through protein channels in the cell membrane in both directions.
E) lose their function, and the water level in the plasma will be maintained by white blood cells instead.

Question 42

If a red blood cell with an internal salt concentration of about 0.85 percent is placed in a solution that is 4 percent salt,

A) the cell will lose water and shrivel.
B) the cell will gain water and burst.
C) the turgor pressure in the cell will increase greatly.
D) the turgor pressure in the cell will decrease greatly.
E) the cell will remain unchanged.

Question 43

When placed in water, wilted plants regain their leaf turgor because of the

A) active transport of salts from the water into the plant cells.
B) active transport of salts from the plant cells into the water.
C) osmosis of water into the plant cells.
D) osmosis of water out of the plant cells.
E) diffusion of water out of the plant cells.

Question 44

Refer to the table below. Which list contains every substance in the table that can be predicted to pass via simple diffusion across a biological membrane?

A) 6, 7
B) 1, 6, 7
C) 2, 3, 5
D) 1, 2, 3, 6
E) 1, 3, 6, 7

Question 45

Refer to the figure below. Which statement regarding the sequence of events shown in the figure is true?

A) The cells in condition B have less turgor pressure than the cells in condition A.
B) The cells in condition A have been placed in a hypotonic solution.
C) The cells in condition C have been placed in a hypertonic solution.
D) The cells in condition C have been placed in an isotonic solution.
E) The cells in condition C have greater turgor pressure than the cells in condition B.

Question 46

If cells that normally contain aquaporins undergo a mutation that destroys aquaporin function, which outcome can be expected?

A) The cells will experience uncontrollable water loss.
B) The cells will experience uncontrollable sodium and potassium ion uptake.
C) The cells will lose the ability to take up or release sodium and potassium ions.
D) The cells' membranes will become impermeable to water.
E) The cells will have no means for any polar compounds to diffuse across their membranes.

Question 47

Refer to the figure below. Which statement regarding the red blood cells in the figure is true?

A) Cell C has been immersed in a hypertonic solution.
B) The concentration of solutes inside cell C is higher than in the solution surrounding the cell.
C) Cell A has been immersed in a hypotonic solution.
D) Osmosis occurs when a cell goes from condition B to C but not from condition B to A.
E) Diffusion of solutes out of the cell is causing the events shown in the transition from condition B to A.

Question 48

Which statement about the process of diffusion is true?

A) The concentration gradient of a solute depends on the size of the molecule.
B) Equilibrium in a solution is the end point of diffusion.
C) The net movement of particles depends on the temperature of the solution.
D) Diffusion is most efficient over long distances.
E) Diffusion can reduce selective permeability of a membrane.

Question 49

Which statement about osmosis is false?

A) Osmosis refers to the movement of water along a concentration gradient.
B) In osmosis, water moves in a direction from low solute concentrations to high solute concentrations.
C) The movement of water across a membrane can affect the turgor pressure of some cells.
D) If osmosis occurs across a membrane, then diffusion is not occurring.
E) Water may move through membrane channels during the process of osmosis.

Question 50

If equal volumes of differently colored solutions are poured into opposite sides of a shallow pool of water, what will be the result at equilibrium?

A) Each solution will be uniformly distributed in the side of the pool into which it was poured.
B) The solutions will be uniformly distributed throughout the pool.
C) Each solution will have moved against its concentration gradient.
D) The concentration of each solution will be higher in one side of the pool than in the other.
E) The solutions will have sunk to the bottom of the pool and remained separate.

Question 51

The directions of ions as they move into and out of the cell are determined by the

A) ability of the ions to let go of their water.
B) ion concentration gradient.
C) number of channel proteins present.
D) size and charge of the ions.
E) presence of specific stimuli to open gated channel proteins.

Question 52

The process of osmosis allows water molecules to pass through specialized channels in membranes.Which statement about osmosis is true?

A) The direction of osmosis depends on temperature.
B) Water will move across a membrane to a region with less solute.
C) Water will move across a membrane to a region with more solute.
D) If the membrane does not allow solutes to pass, water will be equal on both sides.
E) A higher solute concentration on one side of a membrane indicates a higher water concentration on that side.

Question 53

Suppose that a new drug shows promise in treating cancer because it can enter cells by simple diffusion.Which statement about the drug is false?

A) It depends on a specific carrier protein to enter the cells.
B) Diffusion of the drug continues until its concentrations across membranes are in equilibrium.
C) The drug molecules move from areas of higher concentration to areas of lower concentration.
D) Diffusion of the drug molecules is a random process.
E) The rate of its diffusion is affected by temperature.

Question 54

Channel proteins allow ions that would not normally pass through the cell membrane to pass through via the channel.The property of the channel protein that makes this possible is its pore, which is composed of

A) polar amino acid groups.
B) hydrophobic amino acid groups.
C) Ca²⁺.
D) carbohydrates.
E) nonpolar R groups.

Question 55

Which helps ensure the diffusion of glucose into a cell that has a high energy need?

A) A glucose pump
B) Ion channels found in large muscle cells
C) A high number of carrier proteins specific for glucose
D) An extracellular environment high in glucose
E) Additional pores through which water can flow, carrying dissolved glucose

Question 56

A molecule is present at two different concentrations on either side of a membrane.The molecule will have the greatest diffusion rate if the concentration is _______ $\mu$ M on one side and _______ $\mu$ M on the other.

A) 10; 20
B) 20; 30
C) 50; 60
D) 30; 30
E) 15; 50

Question 57

In facilitated diffusion, the diffusion rate of a specific molecule across a membrane does not continue to increase as the molecule's concentration difference across the membrane increases beyond a certain point.The reason is that

A) facilitated diffusion requires the use of ATP.
B) as the concentration difference increases, molecules interfere with one another.
C) the carrier proteins become saturated.
D) the transport protein is a channel protein.
E) the diffusion constant depends on the concentration difference.

Question 58

Which strategy is paired with an appropriate consequence that would enable a cell to maintain homeostasis when placed in a vessel of pure water?

A) Reduce the number of aquaporins in the cell membrane to stop water from moving out of the cytoplasm and into the external environment.
B) Decrease the movement of salts out of the cytoplasm to stop water from moving into the cytoplasm.
C) Expend energy to pump water out of the cytoplasm and into the external environment as the internal fluid levels become too high.
D) Expend energy to pump salts into the cytoplasm from the external environment as the cytoplasm swells from water moving in by osmosis.
E) Allow water to diffuse across the cell membrane until equilibrium is reached.

Question 59

Refer to the figure below. Which statement regarding channel proteins shown in the figure is false?

A) Channel proteins can assist polar molecules to cross the plasma membrane by facilitated diffusion.
B) The gated ion channel can allow ions to pass when stimulated to open.
C) The surface of a channel protein in contact with the bilayer would likely have hydrophilic amino acids.
D) Water plays a role in determining which ions are allowed to pass through an ion channel.
E) Aquaporins are channel proteins that facilitate the diffusion of water across membranes.

Question 60

The difference between osmosis and diffusion is that

A) diffusion is passive transport, whereas osmosis is active transport.
B) only in diffusion do molecules move from areas of high concentration to areas of low concentration.
C) only diffusion refers to the movement of materials across a semipermeable membrane.
D) osmosis refers specifically to the movement of water, whereas diffusion is the movement of any molecule.
E) the process of osmosis varies according to the kinds of particles present.

Question 61

Phagocytosis, pinocytosis, and receptor-mediated endocytosis all involve

A) the intake of large particles.
B) invagination of the plasma membrane.
C) the export of macromolecules.
D) the presence of receptor proteins.
E) the intake of fluids by the cell.

Question 62

Which is not involved in secondary active transport?

A) Energy
B) A coupled transporter
C) A concentration gradient
D) The bilayer membrane
E) A uniporter

Question 63

If a cell were bathed in an extracellular solution high in Na⁺, what type of ion movement would maintain the proper balance of Na⁺ ions between the inside and the outside of the cell?

A) Active transport of Na⁺ against its concentration gradient
B) Facilitated diffusion of Na⁺ through ion channels
C) Secondary active transport of K⁺
D) Simple diffusion of Na⁺
E) Simple diffusion of K⁺

Question 64

Both phagocytosis and receptor-mediated endocytosis

A) are methods used by a cell to expel materials into the environment.
B) involve vesicle formation as materials are taken up from the environment.
C) are nonspecific in terms of the materials they transport.
D) use membrane receptors as recognition sites for the molecules they target.
E) involve a process in which vesicles in the cytoplasm fuse with the cell membrane on the interior of a cell.

Question 65

What term is used to describe the nonspecific uptake of fluids and dissolved solutes by a cell?

A) Osmosis
B) Diffusion
C) Receptor-mediated endocytosis
D) Phagocytosis
E) Pinocytosis

Question 66

In the intestine, Na⁺ and an amino acid bind to the same transport protein that moves the two substances in the same direction.This type of active transport involves

A) a symporter.
B) an antiporter.
C) secondary active transport.
D) facilitated transport.
E) a diffusion mechanism.

Question 67

Both primary and secondary active transport

A) generate ATP.
B) are based on passive movement of Na⁺ ions.
C) include the passive movement of glucose molecules.
D) use ATP directly.
E) can move solutes against their concentration gradients.

Question 68

Secondary active transport occurs in the small intestine, where the uptake of glucose is coupled to the transport of sodium ions into the cells lining this organ.This type of transport system is called

A) a uniporter.
B) a symporter.
C) an exchange channel.
D) diffusion.
E) an antiporter.

Question 69

Which is an example of passive transport?

A) Facilitated diffusion
B) The sodium-potassium pump
C) Turgor pressure
D) ATP-driven transport
E) Endocytosis

Question 70

Refer to the figure below, which is being created to illustrate secondary active transport. The small red circles represent the molecules being transported, and the H⁺ symbols represent hydrogen ions.The natural concentration gradient of the red molecules is shown.The hydrogen ion gradient was established by a membrane protein that is not shown.Given this information, which symbol should appear in the oval to indicate the direction of movement of hydrogen ions and red molecules?

A)
B)
C)
D)
E)

Question 71

Refer to the figure below. According to the graph, as the number of glucose molecules increases, the rate of diffusion across a membrane

A) increases indefinitely.
B) decreases.
C) increases until a plateau is reached.
D) can either increase or decrease.
E) remains unchanged.

Question 72

In passive transport, molecules move

A) against their concentration gradient.
B) more slowly than in active transport.
C) toward a region of higher concentration.
D) so as to reduce differences in concentration across a membrane.
E) until a state of equilibrium is reached and movement stops.

Question 73

Refer to the figure below, which is being created to illustrate secondary active transport. What is missing from the figure?

A) A concentration gradient
B) Arrows showing movement of sodium ions
C) A coupled transporter acting to create a concentration gradient
D) Arrows showing movement of glucose molecules
E) A source of energy for sodium ion transport

Question 74

Facilitated diffusion and active transport both

A) require ATP.
B) require the use of proteins as carriers or channels.
C) carry ions and not small molecules.
D) increase without limit as the concentration gradient increases.
E) depend on the solubility of the solute in lipids.

Question 75

For each molecule of ATP consumed during active transport of sodium and potassium, there is an import of _______ ion(s) and an export of _______ ion(s).

A) two Na⁺; three K⁺
B) two Na⁺; one K⁺
C) one K⁺; three Na⁺
D) two K⁺; three Na⁺
E) three K⁺; two Na⁺

Question 76

Refer to the figure below showing concentrations of three ions inside and outside a cell, as well as the direction of transport of each ion facilitated by a membrane protein. Which ions are moved by active transport and why?

A) K⁺ and Na⁺, because they are present in millimolar concentrations in the cell
B) Ca²⁺, because it is present in concentrations below the micromolar level in the cell
C) K⁺, because it is being moved into the cell and not out of the cell
D) K⁺, Na⁺, and Ca²⁺, because they are charged particles
E) K⁺, Na⁺, and Ca²⁺, because they are moving from lower to higher concentration

Question 77

The sodium‒potassium pump found in animal cells is a(n)

A) uniporter.
B) carrier protein.
C) symporter.
D) peripheral membrane protein.
E) antiporter.

Question 78

Regardless of the specific type of molecule or particle being transported, endocytosis always involves

A) phagocytosis.
B) pinocytosis.
C) receptor proteins.
D) membrane invagination.
E) phagosomes.

Question 79

Transporters that move two substances at once are known as

A) uniporters.
B) facilitated transporters.
C) secondary active transporters.
D) coupled transporters.
E) directional transporters.

Question 80

The sodium‒potassium pump changes shape in response to

A) the binding of ions.
B) the hydrolysis of ATP and phosphorylation.
C) the release of Na⁺ ions outside the cell.
D) the influx of K⁺ ions.
E) secondary active transport.