Deck 4: Movement of Molecules Across Cell Membranes

Question 1

Which of the following statements regarding the structure and function of cell membranes is correct?

A)The phospholipid bilayer is arranged so that the hydrophilic heads of the phospholipid molecule face the extra- and intracellular fluids
B)Some proteins integrated into the membrane serve as channels for the passage of nonpolar molecules through the membrane
C)Some proteins integrated into the membrane function as channels associated with transport of ions through the membrane
D)Both the phospholipid bilayer is arranged so that the hydrophilic heads of the phospholipid molecule face the extra- and intracellular fluids and some proteins integrated into the membrane function as channels associated with transport of ions through the membrane are correct
E)All of the choices are correct

Answer 1

D

Question 2

Which of the following statements regarding the diffusion of nonpolar solutes across cell membranes is correct?

A)At equilibrium for solute X, the flux of X across cell membranes is zero
B)At equilibrium for solute X, the net flux of X across cell membranes is zero
C)At equilibrium for solute X, the concentration of X inside the cell is equal to its concentration outside the cell
D)Both at equilibrium for solute X, the flux of X across cell membranes is zero and at equilibrium for solute X, the concentration of X inside the cell is equal to its concentration outside the cell are correct
E)Both at equilibrium for solute X, the net flux of X across cell membranes is zero and at equilibrium for solute X, the concentration of X inside the cell is equal to its concentration outside the cell are correct

Answer 2

E

Question 3

The permeability of the plasma membrane to mineral ions

A)Is dependent upon channels formed by proteins
B)Varies from one cell to another
C)Is affected by differences in electrical charge on the two sides of the membrane
D)Both is dependent upon channels formed by proteins and is affected by differences in electrical charge on the two sides of the membrane are correct
E)All of the choices are correct

Answer 3

E

Question 4

Which of the following would decrease the rate of diffusion?

A)Increasing the size of the diffusing solute
B)Increasing the temperature
C)Increasing the concentration gradient
D)Increasing the surface area for diffusion
E)All of the choices would increase the rate of diffusion

Question 5

Mediated transport across cell membranes

A)Refers to the movement of ions through protein channels
B)Refers both to diffusion and to the active transport of molecules
C)Is characterized by saturable carriers and a maximum velocity of transport
D)Both refers to the movement of ions through protein channels and refers both to diffusion and to the active transport of molecules are correct
E)Both refers both to diffusion and to the active transport of molecules and is characterized by saturable carriers and a maximum velocity of transport are correct

Question 6

Diffusion

A)Depends upon the random motion of molecules
B)Results in net movement of molecules from regions of low concentration to regions of high concentration
C)Is important for moving molecules over large distances in the body
D)Requires energy in the form of ATP to be carried out
E)Includes all of the choices

Question 7

Which form of membrane transport is being described? The passage of molecules into cells without passing through the plasma membrane's structural matrix.

A)Diffusion
B)Osmosis
C)Facilitated diffusion
D)Endocytosis
E)Apoptosis

Question 8

Ion channels in cell membranes

A)Are nonspecific
B)May open in response to a change in potential difference across the membrane
C)May open in response to binding a ligand
D)Both are nonspecific and may open in response to a change in potential difference across the membrane are correct
E)Both may open in response to a change in potential difference across the membrane and may open in response to binding a ligand are correct

Question 9

The mediated transport of a substance across a plasma membrane

A)Depends upon the binding of that substance to a specific site on the membrane protein
B)Depends upon movement of proteins from one side of the membrane to the other
C)Always increases in direct proportion to the increasing concentration of the substance on one side of the membrane
D)Both depends upon the binding of that substance to a specific site on the membrane protein and depends upon movement of proteins from one side of the membrane to the other are correct
E)All of the choices are correct

Question 10

Carrier-mediated transport

A)Involves a specific membrane protein that functions as a carrier molecule
B)Always involves the movement of substances against a concentration gradient
C)Always requires the direct expenditure of energy
D)Both involves a specific membrane protein that functions as a carrier molecule and always involves the movement of substances against a concentration gradient are correct
E)All of the choices are correct

Question 11

When a solute,X,is placed in compartment A of a two compartment container and allowed to diffuse to compartment B and attain diffusion equilibrium,then

A)There will no longer be any movement of solutes between compartments
B)Solutes will be moving in both directions equally
C)Solutes will only continue to move from A to B
D)Solutes will only continue to move from B to A
E)Solutes will continue to move to the side with the higher concentration

Question 12

The net flux of a penetrating solute into a cell will increase if the

A)Permeability constant for that solute increases
B)Temperature increases
C)Concentration of that solute in the extracellular fluid increases
D)Both permeability constant for that solute increases and concentration of that solute in the extracellular fluid increases are correct
E)All of the choices are correct

Question 13

If it takes solute A 1 second to diffuse 1 millimeter,how long will it take solute A to diffuse 10 millimeters under the same conditions?

A)1 second
B)10 seconds
C)50 seconds
D)100 seconds
E)1000 seconds

Question 14

Which of the following statements regarding the movement of molecules across cell membranes is correct?

A)The diffusion of molecules across a cell membrane occurs at a rate that is influenced by the surface area of the membrane and the magnitude of the concentration difference across it
B)The net flux of molecules that cross cell membranes by diffusion is always from regions of lower concentration to regions of higher concentration
C)Molecules that enter a cell by diffusion must directly permeate the lipid portion of the plasma membrane, whereas those that enter by facilitated diffusion utilize membrane-bound proteins
D)Both the diffusion of molecules across a cell membrane occurs at a rate that is influenced by the surface area of the membrane and the magnitude of the concentration difference across it and the net flux of molecules that cross cell membranes by diffusion is always from regions of lower concentration to regions of higher concentration are correct
E)Both the diffusion of molecules across a cell membrane occurs at a rate that is influenced by the surface area of the membrane and the magnitude of the concentration difference across it and molecules that enter a cell by diffusion must directly permeate the lipid portion of the plasma membrane, whereas those that enter by facilitated diffusion utilize membrane-bound proteins are correct

Question 15

Glucose enters most cells by

A)Diffusion through the lipid bilayer
B)Primary active transport
C)Secondary active transport
D)Diffusion through a protein channel
E)Endocytosis

Question 16

Which of the following is not a difference between primary active transport and secondary active transport?

A)Primary active transport uses energy derived from ATP whereas secondary active transport does not
B)Primary active transport uses a carrier that is an ATPase whereas the latter does not
C)Primary active transport uses a carrier that is phosphorylated whereas the latter does not
D)Primary active transport uses a carrier whose binding affinity for the solute is modified by covalent modulation whereas the latter does not
E)None of the choices are correct

Question 17

Which of the following statements regarding the active transport of molecules across cell membranes is correct?

A)Both primary and secondary active transport are dependent upon energy derived from ATP
B)In secondary active-transport systems in which Na ions are bound to carriers, the actively transported solute always follows Na ions across the membrane
C)In secondary active-transport systems in which Na ions are bound to carriers, the actively transported solute always moves across the membrane in the direction opposite of Na ion movement
D)Both primary and secondary active transport are dependent upon energy derived from ATP and in secondary active-transport systems in which Na ions are bound to carriers, the actively transported solute always follows Na ions across the membrane are correct
E)Both primary and secondary active transport are dependent upon energy derived from ATP and in secondary active-transport systems in which Na ions are bound to carriers, the actively transported solute always moves across the membrane in the direction opposite of Na ion movement are correct

Question 18

Which of the following is a feature that distinguishes active transport from facilitated diffusion?

A)Saturability
B)Requirement for a carrier molecule
C)Specificity
D)Presence of a transport maximum
E)Requirement for metabolic energy

Question 19

Equal concentrations of two solutes,A and B,are placed into the same beaker at the same time.Solute A reaches diffusion equilibrium faster than solute B.What is the most likely explanation for this observation?

A)The temperature was greater for solute A than solute B
B)The concentration gradient for A was greater than B
C)Solute A is smaller than solute B
D)Solute A traveled a shorter distance than solute B
E)All of the choices are logical explanations

Question 20

In general,polar molecules diffuse more rapidly through the lipid bilayer part of cell membranes than do nonpolar molecules.This statement is

A)True
B)False.Polar molecules diffuse through less rapidly because the bilayer is polar throughout its width
C)False.Polar molecules diffuse through less rapidly because the bilayer is nonpolar throughout its width
D)False.Nonpolar molecules diffuse through more rapidly because much of the bilayer is nonpolar
E)False.The rate of diffusion of nonpolar and polar molecules through the bilayer is essentially the same as long as the molecules are the same size

Question 21

A cell is placed into a 1 millimolar solution of substance X and over time you witness the concentration of X inside the cell increase to 5 millimolar.The best explanation for this is:

A)X is moving into the cell by simple diffusion
B)X is moving into the cell by diffusion through a protein channel
C)X is moving into the cell by facilitated diffusion
D)X is moving into the cell by primary active transport
E)It is not possible to tell which mechanism is responsible for the transport of X

Question 22

Which of the following statements about the Na,K pump is false?

A)It transports Na⁺ out of cells and K⁺ into cells
B)It binds to and hydrolyzes ATP
C)It is constantly active in all cells
D)Its activity requires the expenditure of metabolic energy
E)It transports Na⁺ and K⁺ in a 1:1 ratio

Question 23

If a cell is placed into an unknown solution and it shrinks,what can be concluded about the unknown solution?

A)Its nonpenetrating solute concentration was greater than that of the cell
B)Its nonpenetrating solute concentration was less than that of the cell
C)Its nonpenetrating solute concentration was equal to that of the cell
D)Any of the choices are possible

Question 24

An example of a hypertonic solution is

A)200 mM NaCl
B)300 mM glucose
C)100 mM MgCl₂
D)400 mM urea
E)None of the choices are correct

Question 25

If all other conditions remain the same and the concentration of a nonpenetrating solute increases inside a cell,

A)Water will tend to enter the cell because the interior has an increased osmolarity
B)Water will tend to leave the cell because the interior has an increased osmolarity
C)Water will tend to enter the cell because the interior has a decreased osmolarity
D)Water will tend to leave the cell because the interior has a decreased osmolarity
E)The nonpenetrating solute will diffuse across the membrane until its concentration is equal on both sides of the membrane

Question 26

If a cell is placed in a hypotonic solution,it

A)Will swell
B)Will shrink
C)Will stay the same size
D)May swell, shrink or stay the same size, depending upon the concentration of penetrating and nonpenetrating solutes in the solution

Question 27

If pure water and a solution containing a nonpenetrating solute are separated by a membrane that is permeable only to water,

A)Water will diffuse by osmosis until the water concentrations in the two compartments become equal
B)Both water and the solute will diffuse across the membrane down their concentration gradients until a state of equilibrium is established
C)Water will diffuse by osmosis until stopped by opposing hydrostatic pressure
D)No movement will occur between the compartments
E)None of the choices will occur

Question 28

If a cell is placed in a hyperosmotic solution,it

A)Will swell
B)Will shrink
C)Will stay the same size
D)May swell, shrink or stay the same size, depending upon the concentration of penetrating and nonpenetrating solutes in the solution

Question 29

Regarding the tonicity and osmolarity of solutions,which of the following statements is not true?

A)The term "tonicity" refers to the effect that a solution has on the degree of stretch or shrinking of the cell membrane
B)The term "osmolarity" refers to the osmotic properties of a solution, regardless of its tonicity
C)Isotonic solutions are always isoosmotic
D)Hypoosmotic solutions are always hypotonic
E)Hypertonic solutions are always hyperosmotic

Question 30

Which of the following solutions is not isotonic to human cells?

A)300 mM glucose
B)300 mM urea
C)100 mM MgCl₂
D)300 mOsm NaCl

Question 31

The reason solutions for injection or infusion into people normally contain either 150 mM NaCl or 300 mM glucose is that these

A)Solutes are necessary for metabolism
B)Solutions are hypertonic to the blood and cells
C)Solutions are hypoosmotic to the blood and cells
D)Solutions are isotonic to the blood and cells
E)Solutions contain penetrating solutes

Question 32

Once formed inside of the cell most endocytic vesicles will fuse with which organelle for sorting?

A)Endoplasmic reticulum
B)Golgi apparatus
C)Endosome
D)Nucleus
E)Mitochondria

Question 33

Which of the following statements regarding the active transport of solutes across cell membranes is correct?

A)Primary active transporters are ATPases and secondary active transporters are not
B)Secondary active transporters require binding of Na ion on the extracellular side of the membrane to transport other solutes either into or out of the cell
C)Solutes transported across cell membranes by primary active transport include glucose, Na ion and Ca ion
D)Both primary active transporters are ATPases and secondary active transporters are not and secondary active transporters require binding of Na ion on the extracellular side of the membrane to transport other solutes either into or out of the cell are correct
E)All of the choices are correct

Question 34

"Osmosis" refers to the movement of ____________ across semipermeable membranes.

A)Glucose
B)Charged particles
C)Lipid molecules
D)Water
E)Any substance

Question 35

Which form of endocytosis is nonspecific,in that it occurs by the formation of an invagination of the plasma membrane which then fills with interstitial fluid of the immediate area?

A)Active transport
B)Hyperosmotic vesicular entrapment
C)Phagocytosis
D)Pinocytosis
E)Hydrosmosis

Question 36

If the ATP-generating mechanisms in a cell are poisoned and the cell has depleted its ATP reserves,

A)Primary active transport of molecules would cease immediately
B)Secondary active transport of molecules would cease immediately
C)Eventually there will be no potential difference across the membrane
D)Both primary active transport of molecules would cease immediately and secondary active transport of molecules would cease immediately are correct
E)Both primary active transport of molecules would cease immediately and eventually there will be no potential difference across the membrane are correct

Question 37

Which of the following statements regarding endocytosis and exocytosis is correct?

A)Endocytosis is a method by which large molecules may be brought into a cell
B)Exocytosis is a method by which large molecules may be secreted from a cell
C)Pinocytosis is a form of endocytosis; phagocytosis is a form of exocytosis
D)Both endocytosis is a method by which large molecules may be brought into a cell and exocytosis is a method by which large molecules may be secreted from a cell are correct
E)All of the choices are correct

Question 38

The removal of cholesterol from the blood during times when its concentrations are high

A)Is heavily dependent upon the activity of phagocytosis
B)Requires that it be bound to circulating lipoproteins which attach to absorbtive cell membranes
C)Is promoted by the increased production of lipoprotein receptors in the cholesterol absorbing cells
D)Both requires that it be bound to circulating lipoproteins which attach to absorbtive cell membranes and is promoted by the increased production of lipoprotein receptors in the cholesterol absorbing cells are correct
E)All of these choices are correct

Question 39

Receptor mediated endocytosis requires

A)A specific ligand and functional receptors for it on the external plasma membrane
B)The molecular components necessary for the synthesis of clathrin proteins
C)The ability of the cell to synthesize the proteins which compose the receptor protein
D)The genes in chromosomal DNA for both receptor and clathrin proteins be present in the cell
E)All of these choices are correct

Question 40

Cholesterol levels in the blood are regulated via the activity of the liver utilizing the process known as _____,which can be regulated to increase uptake as the cell ______ the number of cholesterol+ lipoprotein receptors on its surface.

A)Phagosomolysis, increases
B)Endosomolysis, decreases
C)Receptor mediated endocytosis, increases
D)Potocytosis, decreases
E)Pinocytosis, increases

Question 41

Molecules increase their rate of diffusion as temperature increases.

Question 42

The concentration of calcium in the cytosol of cells is very much lower than the concentration of extracellular calcium.

Question 43

Because of the active transport of Na⁺ and K⁺,the intracellular concentration of Na⁺ is lower than the extracellular concentration,whereas the reverse is true for K⁺.

Question 44

The greater the concentration difference of a substance between two volumes separated by a permeable membrane,the lesser the magnitude of the net flux of the substance.

Question 45

Potocytosis

A)Involves simple diffusion of low molecular weight molecules across the plasma membrane, following a concentration gradient
B)Is triggered by ligands which lead to the formation of caveolae delivering low molecular weight molecules directly to the cytosol
C)Is the process which directly regulates and often limits receptor mediated endocytosis to remain within homeostatic parameters
D)Involves active transport of high molecular weight lipoprotein complexes through the participation of clathrin in the formation of endosomal vesicles
E)Both is triggered by ligands which lead to the formation of caveolae delivering low molecular weight molecules directly to the cytosol and is the process which directly regulates and often limits receptor mediated endocytosis to remain within homeostatic parameters are correct

Question 46

At any given time it is possible to see endocytotic vesicles docked to intracellular organelles such as those which may receive their contents for modification,synthesis,packaging and then release.Which organelle would be most likely to be involved in this process as a destination for a transport vesicle formed for this purpose along the plasma membrane?

A)Golgi apparatus
B)Peroxisome
C)Lysosome
D)Mitochondrion
E)Ribosome

Question 47

The Na,K pump is an enzyme that phosphorylates itself.

Question 48

Which of the following are possible combinations of mechanisms for transport of a particle against a concentration gradient across an epithelial cell?

A)Passive diffusion from a lumen into the cell followed by facilitated diffusion from the cell into the blood
B)Passive diffusion on the apical side into the cell followed by primary active transport on the basolateral side
C)Secondary active transport on the mucosal side followed by facilitated diffusion on the serosal side
D)Both passive diffusion from a lumen into the cell followed by facilitated diffusion from the cell into the blood and passive diffusion on the apical side into the cell followed by primary active transport on the basolateral side are correct
E)Both passive diffusion on the apical side into the cell followed by primary active transport on the basolateral side and secondary active transport on the mucosal side followed by facilitated diffusion on the serosal side are correct

Question 49

In general,polar molecules diffuse more rapidly across cell membranes than do nonpolar molecules.

Question 50

Which of the following statements about epithelial cells and epithelial transport is correct?

A)Epithelial cells are polarized
B)Epithelial cells lining the small intestine have Na, K-ATPase pumps only in their basolateral membranes
C)The "active" component of active transport across epithelial cells occurs only from the lumen side into the cells
D)Both epithelial cells are polarized and epithelial cells lining the small intestine have Na, K-ATPase pumps only in their basolateral membranes are correct
E)Both epithelial cells are polarized and the "active" component of active transport across epithelial cells occurs only from the lumen side into the cells are correct

Question 51

In active transport,the affinity of any given binding site for the molecule to be transported changes as the site goes from facing one side of the membrane to facing the other side.

Question 52

The component of the plasma membrane that acts as the selective barrier for diffusion is the integral proteins.

Question 53

During the active transport of glucose across an epithelium,energy is used to

A)Power the Na, K-ATPase pump
B)Power the Na-glucose cotransporter
C)Synthesize insulin, which is necessary for glucose reabsorption
D)Maintain the transport maximum for glucose
E)Power the facilitated diffusion of glucose across the basolateral membrane of the epithelial cell

Question 54

At any given concentration difference,the rate of diffusion across a permeable surface will be greater for small molecules than for larger ones.

Question 55

In most of the cells in the body there is an electrical difference such that the inside of cells is positive with respect to the outside.

Question 56

Specific proteins in the membranes mediate movement of lipid-soluble molecules into cells.

Question 57

Integral membrane proteins can form channels through which ions such as Na+ and K+ can diffuse.

Question 58

The final equilibrium state reached by a molecule that enters a cell by facilitated diffusion is the same as that for a molecule that enters the cell by diffusion.

Question 59

Mediated transport is required in order for glucose,amino acids and fatty acids to pass into cells because these substances cannot diffuse through plasma membranes.

Question 60

Although permeability to mineral ions does not vary much from one cell to another,different cells vary considerably in their permeability to nonpolar molecules.

Question 61

The functions of the process known as potocytosis in homeostasis have been extensively studied and are very well known and understood beyond any speculation to include,cell signaling,trans-cellular transport and cholesterol homeostasis.

Question 62

In the body,Na ions behave as if they are nonpenetrating solutes because they are actively transported out of cells.

Question 63

The clathrin protein so important to carrying out receptor mediated transport remains with an endosome as it moves deep within the cell and is degraded entirely along with the ingested internal contents.

Question 64

The fate of all endocytotic vesicles is digestion of their contents by lysosomal enzymes.

Question 65

The luminal side of an epithelial cell is also known as the basolateral side.

Question 66

If a cell were placed in a solution of 0.15 M NaCl,it would shrink.

Question 67

Adding one gram of NaCl to one liter of water will lower the water concentration twice as much as adding one gram of glucose.(The molecular mass of NaCl is 58.5; that of glucose is 180.)

Question 68

Pinocytosis is a method by which molecules can leave cells whose membranes are impermeable to the molecules.

Question 69

A portion of a cell's plasma membrane is removed during endocytosis.

Question 70

Both primary and secondary active transport require the expenditure of metabolic energy.

Question 71

Most cells can perform pinocytosis,but only a few kinds can perform phagocytosis.

Question 72

Receptor mediated endocytosis can be used as an elegant mechanism to that allows for the transport and introduction of a vesicle's contents into another membrane-bound organelle or from one layer of epithelial cells to another.

Question 73

Endocytosis of any kind requires metabolic energy.

Question 74

The intracellular concentration of water in the cells of the body is the same as the extracellular concentration of water.

Question 75

Phagocytic leukocytes use the process to engulf foreign bacteria and destroy them within ribosomes.

Question 76

Adding one mole of NaCl to one liter of water will lower the water concentration twice as much as adding one mole of glucose.

Question 77

The Na,K-ATPase carrier transports sodium ions out of cells and potassium ions into cells on a one-to-one basis.

Question 78

Active transport,facilitated diffusion and osmosis all require the expenditure of metabolic energy.

Question 79

In the body,K ions behave as if they are penetrating solutes because they are actively transported into cells.

Question 80

The higher the osmolarity of a solution,the higher the concentration of water in it.