Deck 4: Movement of Molecules Across Cell Membranes

Question 1

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,because polar molecules diffuse through less rapidly because the bilayer is polar throughout its width.
C)false,because polar molecules diffuse through less rapidly because the bilayer is nonpolar throughout its width.
D)false,because nonpolar molecules diffuse through more rapidly because much of the bilayer is nonpolar.
E)false,because 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.

Answer 1

D

Question 2

The permeability of the plasma membrane to mineral ions:

A)is not influenced by channels formed by proteins.
B)is the same in all cell types.
C)is affected by differences in electrical charge on the two sides of the membrane.
D)is zero in all living cells.
E)is only possible because of the hydrophobic interior of the lipid bilayer.

Answer 2

C

Question 3

Which of the following would decrease the net flux of a penetrating solute into a cell?

A)increasing the permeability constant for that solute
B)decreasing the temperature
C)increasing the concentration of the solute in the extracellular fluid
D)increasing the area of the cell membrane
E)decreasing the thickness of the membrane

Answer 3

B

Question 4

Ion channels in cell membranes:

A)are nonspecific.
B)are not affected by differences in electrical potential across the membrane.
C)may open in response to binding a ligand.
D)only allow ions to move from the extracellular fluid into the cell.
E)only allow ions to move from the intracellular fluid out of the cell.

Question 5

By what transport mechanism does glucose enter most cells?

A)diffusion through the lipid bilayer
B)primary active transport
C)secondary active transport
D)diffusion through a protein channel
E)facilitated diffusion

Question 6

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) Peripheral membrane proteins function as channels associated with transport of ions through the membrane.
D)Cholesterol molecules function to transport ions from one side of the plasma membrane to the other.
E) The plasma membrane is a layer of phospholipid molecules with their hyrophilic head groups in contact with the extracellular solution and the hydrophobic tail groups in contact with the intracellular solution.

Question 7

Which of the following statements regarding the diffusion of a nonpolar solute X across a cell membrane is correct?

A)At equilibrium the net flux of X across the cell membrane is zero.
B)At equilibrium,X will cease moving across the cell membrane.
C)Solute X will be unable to reach equilibrium because it is nonpolar.
D)Solute X will reach equilibrium,but the concentration will be much higher on the inside of the cell because of the smaller volume.
E)At equilibrium,movement of X across the membrane will be much faster in one direction than in the other.

Question 8

If all other conditions remain the same and the concentration of a nonpenetrating solute increases inside a cell,which is most likely to occur?

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 solute will diffuse across the membrane until its concentration is equal on both sides of the membrane.

Question 9

"Osmosis" refers to the movement of what substance across semipermeable membranes?

A)glucose
B)charged particles
C)lipid molecules
D)water
E)solutes

Question 10

Which of the following statements about the Na+-K+ ATPase 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 11

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.What is the best explanation for this observation?

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)Water is leaving the cell by osmosis.

Question 12

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

A)saturation of transport rate
B)requirement for a carrier molecule
C)carrier molecules have specificity
D)presence of a transport maximum
E)requirement for metabolic energy

Question 13

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

A)Water will diffuse by osmosis until the water concentrations in the two compartments become equal.
B)Water will diffuse by osmosis until all of the the water is on the same side as the solute.
C)Water will diffuse by osmosis toward the side with the solute,until stopped by opposing hydrostatic pressure.
D)No movement will occur between the compartments.
E)Water will diffuse by osmosis away from the side with the solute,until stopped by hydrostatic pressure.

Question 14

What is the best description of a secondary active transport process that cotransports an amino acid with Na+?

A)Both Na+ and the amino acid bind on the side of the membrane where the Na+ concentration is lowest,and undergo net movement to the other side of the membrane.
B)Na+ and the amino acid bind to opposite sides of the membrane,and Na+ undergoes net transport from the side of the membrane with higher Na+ concentration toward the side with lower concentration,while the amino acid moves in the opposite direction.
C)Both Na+ and the amino acid bind on the side of the membrane where the Na+ concentration is higher,and both are transported to the side of the membrane where the Na+ concentration is lower.
D)Both Na+ and the amino acid bind to the side of the membrane where the amino acid concentration is highest and are transported toward the side of the membrane where the amino acid concentration is lower.
E)Na+ and the amino acid bind to opposite sides of the membrane,and the amino acid undergoes net transport from the side of the membrane with lower Na+ concentration to the side of the membrane where the Na+ concentration is higher.

Question 15

Which is a form of cellular transport that involves the movement 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 16

Which is TRUE regarding diffusion?

A)It depends upon the random motion of molecules.
B)It results in net movement of molecules from regions of low concentration to regions of high concentration.
C)It is the principle mechanism by which molecules are moved over large distances in the body.
D)It requires energy in the form of ATP.
E)It requires integral membrane proteins to occur.

Question 17

Which is true about mediated transport across cell membranes?

A)It refers to the movement of ions through protein channels.
B)It refers both to simple diffusion and to the active transport of molecules.
C)It is characterized by saturable carriers and a maximum velocity of transport.
D)As the concentration gradient across a membrane increases,the transport rate always increases.
E)It is nonspecific; any transporter can transport any molecule across the cell membrane.

Question 18

Which is true regarding the mediated transport of a substance across a plasma membrane?

A)It depends upon the binding of that substance to a specific site on the membrane protein.
B)It depends upon movement of proteins from one side of the membrane to the other.
C)It 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 19

Which is true about mediated transport of substances across cell membranes?

A)It involves a specific membrane protein that functions as a carrier molecule.
B)It always involves the movement of substances against a concentration gradient.
C)It is always directly coupled to the splitting of ATP molecules.
D)There is no limit to how fast it can occur as the concentration gradient becomes larger.
E)It is the main mechanism for transporting hydrophobic molecules across membranes.

Question 20

If the ATP-generating mechanisms in a cell are poisoned and the cell depletes its ATP reserves,which would occur first?

A)Primary active transport of molecules would cease.
B)Secondary active transport of molecules would cease.
C)Facilitated diffusion of molecules would cease.
D)Ion concentration gradients would reach equilibrium across the cell membrane.
E)All transport processes would cease immediately when the ATP was depleted.

Question 21

What will happen if a normal cell is placed in a hyperosmotic solution?

A)It will swell in size.
B)It will shrink in size.
C)It will stay the same size.
D)It may swell,shrink,or stay the same size,depending upon the concentration of penetrating and nonpenetrating solutes in the solution.

Question 22

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 23

What process lowers blood plasma levels of cholesterol-containing lipoproteins?

A)second messenger-activated,sterol transgenesis
B)hydrophobic phagocytosis
C)simple,transcellular membrane diffusion
D)Na+ gradient-dependent,secondary active transport
E)clathrin-dependent,receptor-mediated endocytosis

Question 24

What will happen if a normal cell is placed in a hypotonic solution?

A)It will swell in size.
B)It will shrink in size.
C)It will stay the same size.
D)The result can't be predicted.

Question 25

What type of cellular transport involves the cytosolic protein clathrin?

A)exocytosis
B)receptor-mediated endocytosis
C)primary active transport
D)secondary active transport
E)pinocytosis

Question 26

Why do solutions for injection or infusion into people with low blood volume normally contain 150 mM NaCl?

A)This is a hypotonic solution,which will cause water movement into dehydrated blood cells.
B)This is an isotonic solution,and the water in it will follow Na and Cl into the the intracellular fluid compartment.
C)This is a hypertonic solution,which will raise the blood volume and pressure more rapidly than an isotonic solution would.
D)This is an isotonic solution,and NaCl will keep the added volume in the extracellular fluid compartment.
E)NaCl are penetrating solutes,which will get them more quickly into blood cells to increase their volume.

Question 27

What is the most common transport mechanism by which glucose and other organic solutes cross the luminal membrane of an epithelial cell layer?

A)secondary active cotransport with Na+
B)glucose ATPase pump
C)facilitated diffusion
D)simple diffusion through the paracellular pathway
E)through an ion channel

Question 28

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

A)Its nonpenetrating solute concentration is greater than that of a normal cell.
B)Its nonpenetrating solute concentration is less than that of a normal cell.
C)Its nonpenetrating solute concentration is equal to that of a normal cell.
D)Its penetrating solute concentration is less than that of a normal cell.
E)Its penetrating solute concentration is greater than that of a normal cell.

Question 29

All other factors being equal,the rate of diffusion across a permeable surface will be greater for small molecules than for larger ones.

Question 30

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

A)150 mM NaCl
B)300 mM urea
C)100 mM MgCl₂
D)300 mOsm NaCl

Question 31

Which of the following statements about epithelial cells and epithelial transport is NOT correct?

A)Epithelial cell membranes express different transport proteins on different cell surfaces.
B)Epithelial cells lining the small intestine have Na,K-ATPase pumps only in their basolateral membranes.
C) The plasma membrane of epithelial cells that faces the inside of a hollow or fluid-filled chamber in the body is called the basolateral membrane.
D)The pathway taken by substances that flow between epithelial cells is called the paracellular pathway.
E)When substances cross epithelial barriers by going through the cell membranes and cytosol,it is called the transcellular pathway.

Question 32

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 33

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

A)Endocytosis is a method by which large molecules may be secreted from 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 type of exocytosis.
D)Pinocytosis is a form of exocytosis; phagocytosis is a type of endocytosis.
E)Pinocytosis and phagocytosis are both types of exocytosis.

Question 34

Which of these is an example of a hypertonic solution?

A)200 mM NaCl
B)300 mM glucose
C)100 mM MgCl₂
D)400 mM urea
E)100 mM NaCl

Question 35

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 36

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

Question 37

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 38

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 39

Which lists the epithelial cell barrier compartments in the order of the typical Na+ concentrations,from highest to lowest?

A)intracellular,lumen side,blood side
B)blood side,lumen side,intracellular
C)blood side,intracellular,lumen side
D)lumen side,intracellular,blood side
E)lumen side,blood side,intracellular

Question 40

Molecules increase their rate of diffusion as temperature increases.

Question 41

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 42

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

Question 43

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

Question 44

The component of the plasma membrane that acts as a selective barrier to diffusion of polar molecules is the integral proteins.

Question 45

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 46

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

Question 47

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

Question 48

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 49

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

Question 50

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

Question 51

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

Question 52

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 53

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 54

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 55

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

Question 56

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

Question 57

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

Question 58

The Na/K ATPase pump is an enzyme that phosphorylates itself.

Question 59

Mediated transport is required in order for glucose,amino acids,and fatty acids to pass into cells because none of these substances can diffuse through plasma membranes.

Question 60

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

Question 61

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

Question 62

Endocytosis of any kind requires metabolic energy.

Question 63

Most organic solutes cross epithelial membranes by simple diffusion on the lumen side followed by active transport across the blood side of the membrane.

Question 64

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

Question 65

The plasma membranes of epithelial cells facing the lumen of hollow organs or tubes have the same transport proteins as the plasma membranes that face the interstitial fluid.

Question 66

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

Question 67

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

Question 68

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

Question 69

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

Question 70

The clathrin protein involved in 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 71

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

Question 72

Net movement of solute across an epithelium that is permeable to water is always accompanied by movement of water in the opposite direction.