Question 1

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

Accepted Answer

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.F) A) and E)
G) None of the above

Question 2

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

Accepted Answer

A) True 
 B)False

Question 3

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?

Accepted Answer

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.F) None of the above
G) B) and D)

Question 4

Endocytosis of any kind requires metabolic energy.

Accepted Answer

A) True 
 B)False

Question 5

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

Accepted Answer

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

Question 6

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

Accepted Answer

A) True 
 B)False  True

Question 7

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

Accepted Answer

A) True 
 B)False

Question 8

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

Accepted Answer

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.F) A) and C)
G) C) and D)

Question 9

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

Accepted Answer

A) True 
 B)False

Question 10

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

Accepted Answer

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.F) C) and D)
G) B) and C)

Question 11

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

Accepted Answer

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 energyF) C) and D)
G) A) and E)

Question 12

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

Accepted Answer

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.F) A) and E)
G) B) and C)

Question 13

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.

Accepted Answer

A) True 
 B)False

Question 14

Ion channels in cell membranes:

Accepted Answer

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.F) A) and C)
G) A) and E)

Question 15

Which is true about mediated transport across cell membranes?

Accepted Answer

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.F) B) and D)
G) B) and C)

Question 16

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

Accepted Answer

A) True 
 B)False  True

Question 17

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+.

Accepted Answer

A) True 
 B)False

Question 18

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

Accepted Answer

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,intracellularF) A) and B)
G) A) and E) B

Question 19

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

Accepted Answer

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.F) A) and B)
G) B) and C)

Question 20

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.

Accepted Answer

A) True 
 B)False

Exam 4: Movement of Molecules Across Cell Membranes

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

Endocytosis of any kind requires metabolic energy.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedTrue

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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.

Correct AnswerverifiedShow Answer

Ion channels in cell membranes:

Correct AnswerverifiedShow Answer

Which is true about mediated transport across cell membranes?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedTrue

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+.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedB

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

Correct AnswerverifiedShow Answer

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.

Correct AnswerverifiedShow Answer

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True

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True

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⁺.

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B

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