Deck 4: Movement of Solutes and Water Across Cell Membranes

Question 1

At a very low temperature known as absolute zero,there is no random molecular motion.At absolute zero,would diffusion occur?

A)No,because diffusion depends upon the random motion of molecules.
B)Yes,because diffusion rates are temperature-independent.
C)Yes,as long as concentration gradients still exist.
D)Yes,because diffusion can use energy in the form of ATP.
E)Yes,as long as integral membrane proteins are still intact.

Answer 1

A

Question 2

You are designing a drug.You'd like to deliver the drug by creating a skin patch that is impregnated with the drug and allowing the drug to diffuse through the layers of the skin to reach the underlying tissues and bloodstream.Which of these chemical changes might you make to increase the number of drug molecules that diffuse through the layers of skin cells?

A)Increasing the number of ionized groups in the drug
B)Increasing the number of nitrogen atoms in the drug
C)Decreasing the number of nonpolar groups in the drug
D)Decreasing the number of polar groups in the drug
E)Increasing the number of oxygen atoms in the drug

Answer 2

D

Question 3

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.

Answer 3

A

Question 4

The concentrations of two substances are increasing outside the cell.For substance A,transport into the cell increases proportionally as the concentration outside increases.For substance B transport into the cell increases but then levels off despite the concentration outside continuing to increase.What is the explanation for this?

A)Competition
B)Saturation
C)Specificity
D)Affinity

Question 5

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 6

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 7

You examine a cell by electron microscopy and find a molecule on the outside of the cell and in vesicles in the cytoplasm.The most likely explanation is that this substance moved into the cell by

A)diffusion.
B)osmosis.
C)facilitated diffusion.
D)endocytosis.
E)apoptosis.

Question 8

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.

Question 9

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.

Question 10

Substance A,a penetrating solute,crosses the membrane at a rate of 10 molecules per second.When a patient has a fever and body temperature is elevated,we would expect the cell to have a rate of

A)less than 10 molecules per second.
B)10 molecules per second.
C)more than 10 molecules per second.

Question 11

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 12

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 13

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 14

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 15

CO₂ is a small,non-polar molecule.It will cross the cell membrane by

A)simple diffusion.
B)diffusion through a channel.
C)active transport.
D)diffusion using a pump.

Question 16

A solute,X,is placed in compartment A of a two compartment container and allowed to diffuse to compartment B and attain diffusion equilibrium.At that point in time,

A)there will be no further movement of any solute molecules 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)the concentration in compartment B will be much higher than that in compartment A.

Question 17

Red blood cells have a higher proportion of aquaporins on the membrane than skin cells do.Assuming equal osmotic pressures,which is true?

A)The rate of osmosis is faster in skin cells than red blood cells.
B)The rate of osmosis is faster in red blood cells than in skin cells.
C)The rate of diffusion for non-polar molecules is faster in red blood cells than skin cells.
D)The rate of diffusion for non-polar molecules is faster in skin cells than red blood cells.
E)No significant differences in osmosis or diffusion rates between these cells.

Question 18

Equal amounts of two solutes,A and B,are placed into the same beaker of water 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)Solute B is more soluble in water than solute A.

Question 19

Substance X is a mostly polar molecule and Substance Y is a mostly non-polar molecule of a similar size.Which will diffuse from the extracellular fluid to the intracellular fluid faster if they are in equal concentrations outside and inside the cell?

A)Substance X will diffuse faster.
B)Substance Y will diffuse faster.
C)Substance X and Substance Y will diffuse at the same rate,as they are of equal size and concentration.

Question 20

The human hormone estrogen is highly nonpolar.After being secreted,estrogen will be found

A)at low concentrations in all cells of the body.
B)at high concentrations just in the cells that express a membrane-bound receptor.
C)trapped in endocytic vesicles in cells that express a membrane-bound receptor.
D)in the lysosome of all cells of the body.

Question 21

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 22

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 23

During a lab experiment,you forgot to label your solution containers.You see that red blood cells were placed into an unlabeled solution and they shrunk.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 24

You are examining the data from two time points taken in an experiment.At time 1 there was an extracellular concentration of Na⁺ of 115 mM outside the cell and 8mM inside the cell.An amino acid,lycine,is at 20mM outside and 40mM inside.At the second time measured Na⁺ is 100mM outside the cell and 23 mM inside the cell.Lycine is 15 mM outside the cell and 45mM inside.What is the best explanation?

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 lower and are transported toward the side of the membrane where the amino acid concentration is higher.
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 25

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 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 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

Which of the following statements regarding endocytosis or 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 28

Which would be true if substance X was moving into a cell by primary active transport?

A)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.
B)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 1 millimolar.
C)A cell is placed into a 1 millimolar solution of substance X and over time you witness the concentration of X inside the cell decrease to 0.5 millimolar.
D)A cell is placed into a 1 millimolar solution of substance X and over time you witness the size of the cell shrink.
E)A cell is placed into a 1 millimolar solution of substance X and over time you witness the size of the cell swell.

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

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 31

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 32

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 33

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 34

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 35

Cholesterol-containing lipoproteins are cleared from the blood by which process?  

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 36

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

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

Question 37

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 38

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 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 39

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 40

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 41

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

Question 42

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 43

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 44

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

Question 45

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 46

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 47

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 48

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 49

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

Question 50

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 51

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

Question 52

Molecules increase their rate of diffusion as temperature increases.

Question 53

The Greater the Concentration Difference of a Substance Between Two Solutions Separated by a Permeable Membrane,the Lesser the Magnitude of the Net Flux of the Substance.

Question 54

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

Question 55

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

Question 56

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 57

Which of the following statements about epithelial cells or 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 face 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 58

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

Question 59

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

Question 60

At any given time it is possible to see endocytotic vesicles docked to intracellular organelles such as those that may receive their contents for modification,synthesis,packaging,and then release.Which organelle would most likely 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 61

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

Question 62

In any given tissue,the side of an epithelial cell further from the nearest blood vessel would be the basolateral side. 

Question 63

A woman is participating in a competition held by a local radio station.To win,she must drink 8 gallons of pure water within a few hours.As the osmolarity of her body fluids decreases,it is possible that her cells,including cells in the brain,may swell and burst.

Question 64

Endocytosis of any kind requires metabolic energy.

Question 65

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 66

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 67

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

Question 68

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

Question 69

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

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

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

Question 72

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

Question 73

Transport of solute molecules across an epithelium is often used to create osmotic pressure and therefore direct the movement of water molecules.

Question 74

A disease that resulted in defective Na⁺/K⁺ pumps would have no effect on the absorption of water across an epithelial surface. 

Question 75

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 76

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

Question 77

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

Question 78

A pediatric patient presents with recurring bacterial infections.This could be due to a defect in phagocytosis.

Question 79

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

Question 80

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