Deck 4: Cell Membrane Transport

Question 1

When molecules are passively transported across a membrane, the direction of their movement is dictated by the molecule's tendency to move

A) into a cell.
B) from lower to higher energy.
C) from higher to lower energy.
D) out of a cell.
E) in both directions; there is no preference.

Answer 1

C

Question 2

When more than one ion species (i.e., Na⁺ and K⁺) is present on both sides of the membrane, the chemical driving force acting on Na⁺ will include

A) all ions present.
B) all positively charged ions.
C) all negatively charged ions.
D) sodium only.
E) the most concentrated ion only.

Answer 2

D

Question 3

As an ion moves passively across a membrane into the cell, the progressive increase in concentration within the cell will

A) cause a switch to facilitated diffusion.
B) increase the net flux across the membrane.
C) decrease the need for active transport to continue transporting.
D) accelerate the rate of diffusion.
E) decrease the net flux across the membrane.

Answer 3

E

Question 4

Which of the following can be used to determine an ion's equilibrium potential?

A) Nernst equation
B) intracellular voltmeter
C) concentration of an ion only
D) Navier -Stokes equation
E) oscilloscope

Question 5

If a positively charged ion is more concentrated outside the cell, the electrical forces required to balance the chemical gradient would be directed . Thus, the equilibrium potential for this
Ion would be charged.

A) outward : positively
B) outward : negatively
C) outward : neutrally
D) inward : negatively
E) inward : positively

Question 6

Based solely upon its electrical charge, the inside of a typical cell will tend to attract extracellular to move inward.

A) proteins
B) anions
C) uncharged ions
D) ions whose concentration gradient allows them
E) cations

Question 7

The unequal distribution of charge in solutions on either side of a membrane will lead to a of charge across the membrane and a membrane.

A) collection : restriction
B) buildup : restriction
C) separation : restriction
D) separation : clustering
E) collection : clustering

Question 8

Which of the following is NOT a determinant of the magnitude and direction of the equilibrium potential for an ion?

A) lipid solubility of the ion
B) charge of the ion
C) concentration gradient
D) chemical driving force
E) valence of the ion

Question 9

Chloride has an equilibrium potential of -90 mV. What direction are the chemical and electrical forces acting on the anion at the resting membrane potential ( -70 mV)?

A) The chemical force is directed into the cell and the electrical force is directed out of the cell.
B) Both the chemical and electrical forces are directed out of the cell.
C) The chemical force is directed out of the cell and the electrical force is directed into the cell.
D) Both the chemical and electrical forces are directed into the cell.
E) There is insufficient information to answer this question.

Question 10

Molecules tend to move spontaneously their chemical gradient.

A) up
B) around
C) down
D) over
E) through

Question 11

If a positively charged ion is more concentrated inside the cell, the electrical forces required to balance the chemical gradient would be directed . Thus, the equilibrium potential for this
Ion would be charged.

A) outward : positively
B) outward : neutrally
C) inward : negatively
D) outward : negatively
E) inward : positively

Question 12

Of the gradients listed below, which is the MOST accurate description of the force that ultimately determines the movement of ions across the membrane?

A) electrochemical gradient
B) chemical gradient
C) electrical gradient
D) potential gradient
E) concentration gradient

Question 13

Which of the following is found in greater concentration inside the cell than outside?

A) water
B) sodium
C) chloride
D) calcium
E) potassium

Question 14

Which of the following is a reflection of the unequal distribution of positive and negative ions across the plasma membrane?

A) chemical gradient
B) chemical driving force
C) electrochemical driving force
D) extracellular potential
E) membrane potential

Question 15

Comparing intracellular to extracellular fluid, the intracellular fluid has a charge relative to the outside of a cell due to the presence of more

A) positive : anions
B) negative : cations
C) positive : cations
D) negative : anions
E) neutral : cations

Question 16

What is responsible for the unequal distribution of ions across a membrane, thereby causing a charge?

A) the semipermeable membrane
B) the concentration of carrier proteins in the membrane
C) the concentration of impermeable charged molecules
D) the concentration of ions seeking equilibrium with respect to their charge
E) the ability of permeable ions to pass through a membrane

Question 17

The potassium equilibrium potential is -94 mV. What does this mean?

A) At the resting membrane potential of neurons, potassium is at equilibrium.
B) At -94 mV, the chemical force for potassium movement is zero.
C) At -94 mV, the electrical force for potassium movement is zero.
D) At -94 mV, potassium movement is opposed exactly by sodium movement.
E) At -94 mV, the chemical force for potassium movement is opposed exactly by the electrical force.

Question 18

The chemical force for which of the following ions is directed into the cell?

A) sodium only
B) calcium only
C) potassium only
D) both potassium and sodium
E) both sodium and calcium

Question 19

Which of the following cells would have a greater electrical attraction for sodium ions to enter the cell?

A) cell with membrane potential = -50 mV
B) cell with membrane potential = 0 mV
C) cell with membrane potential = -70 mV
D) cell with membrane potential = -90 mV
E) cell with membrane potential = +20 mV

Question 20

If the solutions on either side of the membrane have an unequal distribution of charged ions, with the inside having an excess of anions, then the inside of the cell would have to be

A) more positive, relative to the outside of the cell.
B) less highly charged than the outside of the cell.
C) more negative, relative to the outside of the cell.
D) less negative, relative to the outside of the cell.
E) more highly charged than the outside of the cell.

Question 21

The equilibrium potential describes the membrane potential where what two forces are balanced?

A) chemical and electrical
B) density and magnetic
C) electrical and permeability
D) temperature and density
E) chemical and temperature

Question 22

Which of the following pairs of characteristics is more likely to make a substance diffuse through the cell membrane?

A) small, polar molecule
B) large, non -polar molecule
C) large, amphipathic molecule
D) small, non -polar molecule
E) large, polar molecule

Question 23

If a cell's Na⁺/ K⁺ pump worked in reverse and had more leak channels for Na⁺ than for K⁺, what would the ion concentrations of the cell look like?

A) Intracellular Cl ^-would be increased, following Na⁺.
B) Intracellular anions would decrease in number.
C) Intracellular concentration of K⁺ would still be higher than Na⁺ because the body tries to maintain an extracellular concentration of Na⁺ at 145 mM.
D) The cell would swell since water follows Na⁺.
E) Although the body tries to maintain an extracellular concentration of Na⁺ at 145mM, the intracellular concentration of Na+ would still be higher.

Question 24

The diffusion rate is

A) the speed at which diffusion takes place.
B) the amount of time necessary for diffusion to take place.
C) the thickness of the membrane through which a material has to diffuse.
D) the amount of material to diffuse through a membrane.
E) fastest at body temperature.

Question 25

An anion is found in greater concentration inside the cell than outside. Which of the following statements BEST describes forces acting on the anion at the resting membrane potential ( -70 mV)?

A) The chemical force is directed into the cell and the electrical force is directed out of the cell.
B) Both the chemical and electrical forces are directed out of the cell.
C) The chemical force is directed out of the cell and the electrical force is directed into the cell.
D) Both the chemical and electrical forces are directed into the cell.
E) There is insufficient information to answer this question.

Question 26

Which of the following is NOT required to determine equilibrium potential of a particular ion?

A) charge or valence of the ion
B) concentration gradient for ion across the membrane
C) temperature
D) the log of the concentration ratio
E) size of the ion

Question 27

Which of the following will NOT increase the net flux of an ion across a membrane?

A) enhanced surface area
B) reduced surface area
C) increased concentration gradient across the membrane
D) more channels for that ion in the membrane
E) elevated permeability of the membrane

Question 28

With pulmonary hypertension, the lung's capillary walls become thicker to compensate for the higher pressure. What does Fick's law suggest will happen to CO₂ concentrations?

A) CO₂ levels in the tissues will decrease.
B) CO₂ levels in the blood will remain the same.
C) CO₂ in the alveoli will increase.
D) CO₂ levels in the blood will increase.
E) CO₂ levels in the cells will decrease.

Question 29

Which of the following is NOT true for all three of these transport mechanisms: facilitated diffusion, primary active transport, and secondary active transport?

A) The transport mechanism is specific for (a) particular solute(s).
B) The transport mechanism requires energy.
C) The transport mechanism has a limit to the total number of molecules that can be transported per unit of time.
D) The transport mechanism requires a protein.
E) Transport can be increased by increasing the number of transport molecules in the plasma membrane.

Question 30

As a cell's metabolism increases, so does its O₂ consumption, giving rise to what product at a ratio of 2:1?

A) lactic acid
B) ATP
C) H₂O
D) pyruvic acid
E) CO₂

Question 31

The equilibrium potential for a cation is +120 mV. Which of the following statements is TRUE when a cell is at the resting membrane potential ( -70 mV)?

A) The chemical force is directed into the cell and the electrical force is directed out of the cell.
B) Both the chemical and electrical forces are directed out of the cell.
C) The chemical force is directed out of the cell and the electrical force is directed into the cell.
D) Both the chemical and electrical forces are directed into the cell.
E) There is insufficient information to answer this question.

Question 32

Which of the following would NOT increase the rate of simple diffusion across the phospholipid bilayer of the plasma membrane?

A) smaller size
B) greater concentration gradient
C) greater lipid solubility
D) greater available surface area
E) greater number of protein carriers

Question 33

If a molecule crosses a membrane and is quickly removed from the area by the blood stream or some biological pathway, what effect does this have on its rate of diffusion?

A) Diffusion rate will not be affected.
B) Diffusion rate will increase.
C) Diffusion rate will remain constant.
D) Diffusion rate will progressively decrease until zero.
E) Diffusion rate will decrease.

Question 34

The concentration of sodium is greater in the extracellular fluid compared to the intracellular fluid. If the membrane potential was equal to the equilibrium potential for sodium, then what would be the direction of the electrochemical force acting on sodium?

A) inward
B) outward
C) equal in both directions
D) varies by cell
E) varies based on concentration of potassium in the intracellular and extracellular fluids

Question 35

When a substance crossing the membrane is driven by diffusion, the net flux of that molecule can be described mathematically by

A) the Goldman -Hodgkin -Katz equation.
B) Fick's law.
C) the Nernst equation.
D) the Navier -Stokes equation.
E) Einstein's equation.

Question 36

What effect would increasing the extracellular concentration of K⁺ have on the resting membrane potential (RMP)?

A) Increasing extracellular K⁺ will have no effect on the RMP because it displaces Na⁺.
B) The RMP would become more negative.
C) Increasing extracellular K⁺ will have no effect on the RMP because of the Na⁺/ K⁺ pump.
D) The RMP would become more positive (less negative).
E) The effects are really seen on the generating potential.

Question 37

Which of the following molecules is LEAST likely to diffuse through the phospholipid bilayer of the plasma membrane?

A) steroids
B) oxygen
C) disaccharide
D) water
E) fatty acid

Question 38

One way that membrane surface area is increased in absorptive cells is through increasing the of the apical membrane.

A) number of protein channels
B) folding
C) number of protein carriers
D) receptor number
E) thickness

Question 39

Oxygen diffuses from blood into cells down its concentration gradient. As cells become more active and oxidative phosphorylation increases in the cell, which of the following occurs?

A) The concentration gradient for oxygen and its rate of movement into the cell do not change.
B) The concentration gradient for oxygen decreases and oxygen movement into the cell increases.
C) The concentration gradient for oxygen decreases and oxygen movement into the cell decreases.
D) The concentration gradient for oxygen increases and oxygen movement into the cell increases.
E) The concentration gradient for oxygen increases and oxygen movement into the cell decreases.

Question 40

Molecules with a relatively high lipid solubility are capable of crossing the membrane

A) directly through the lipid bilayer.
B) only with the addition of energy.
C) only through specific protein channels.
D) indirectly by moving across a carrier protein.
E) through specific lipid channels.

Question 41

A carrier is a transmembrane protein that moves molecules across the membrane through

A) a water -filled pore.
B) small gaps in the fluid portion of the membrane.
C) opening its gate and allowing molecules through.
D) conformational changes in its protein shape.
E) a lipid -filled pore.

Question 42

What transport process couples the movement of an ion against its electrochemical gradient to another ion that is moving down its electrochemical gradient that was established using cellular energy (ATP)?

A) primary active transport
B) secondary active transport
C) tertiary passive transport
D) primary passive transport
E) secondary passive transport

Question 43

Most water molecules that cross the plasma membrane do so by

A) diffusion through aquaporins.
B) diffusion through the plasma membrane.
C) diffusion through ion channels.
D) active transport by aquaporins.
E) active transport by ion channels.

Question 44

Na⁺ is released from its binding site on the Na⁺/ K⁺ pump as a result of the

A) enzyme on the inside of the cell which cleaves the Na⁺ from its binding site.
B) conformational change decreasing the affinity of the Na⁺ binding site.
C) interaction of the Na⁺ and K⁺ binding sites.
D) binding of K⁺ to its binding site.
E) exposure of the Na⁺ binding site to the inside of the cell.

Question 45

In active transport, the affinity of the carrier protein for the molecule being transported is greater on which side of the membrane?

A) always the side facing the intracellular fluid
B) always the side facing the extracellular fluid
C) on the side where the molecule is in lower concentration
D) on the side where the molecule is in greater concentration
E) Neither; it is equal on both sides of the membrane.

Question 46

In general, the molecules that move through specific carrier proteins are determined by which of the following?

A) the molecule's lipid solubility
B) a water -filled pore
C) the unique fit to binding sites on the channel or carrier protein
D) the size of a molecule
E) conformational changes in the pore

Question 47

Which of the following statements about Ca²⁺ pumps is FALSE?

A) It is a form of primary active transport.
B) Calcium is actively transported from an organelle into the cytosol.
C) Calcium is actively transported from the cytosol into the extracellular fluid.
D) The pump is also an ATPase.
E) It maintains low cytosolic calcium levels.

Question 48

The concentration of an anion inside a cell is 0.3%. The concentration of this anion outside the cell is 0.1%. How could the cell obtain more of this ion inside the cell?

A) passive transport
B) osmosis
C) active transport
D) exocytosis
E) pinocytosis

Question 49

During cotransport of glucose with sodium, sodium increases the affinity of the carrier molecule for glucose when the binding site is facing which side?

A) the extracellular fluid
B) Cotransport does not involve changes in affinity of the carrier molecule.
C) Sodium decreases the affinity of the carrier for glucose; it does not increase affinity.
D) Both sides are affected equally.
E) the intracellular fluid

Question 50

Which of the following statements about glucose cotransport with sodium is TRUE?

A) Glucose moves into the cell while sodium moves out of the cell.
B) Glucose moves out of the cell while sodium moves into the cell.
C) Glucose and sodium both move into the cell.
D) Glucose and sodium both move out of the cell.
E) Sodium moves out of the cell, but the movement of glucose will vary based on the type of cell.

Question 51

The first step of the Na⁺/ K⁺ pump's activity involves the binding of which of the following?

A) 3 Na⁺ and 2 K⁺ to their respective binding sites
B) 3 Na⁺ to their binding site on the inside of the cell
C) 3 Na⁺ to their binding site on the outside of the cell
D) 2 K⁺ to their binding site on the inside of the cell
E) 2 K⁺ to their binding site on the outside of the cell

Question 52

What effect does uncontrolled diabetes mellitus have on blood osmolarity?

A) none
B) It increases it, causing a hyperosmotic state compared to normal.
C) It decreases it, causing a hyperosmotic state compared to normal.
D) It decreases it, causing a hypo -osmotic state compared to normal.
E) It increases it, causing a hypo -osmotic state compared to normal.

Question 53

When the Na⁺/ K⁺ pump moves its bound molecules of Na⁺ to the outside of the membrane, it

A) releases the bound ATP to return to its normal confirmation.
B) pumps more K⁺ back into the cell than the amount of Na⁺ that just came out.
C) cannot return to the inside empty -handed, so it must bind two K⁺ first.
D) immediately returns to the inside of the cell, ready to transport more Na⁺ back outside.
E) binds to ATP to release the energy required to power the return trip.

Question 54

Transporting a substance against its concentration gradient requires

A) a transporter that is facilitated in its diffusion.
B) a channel that is specific for that substance.
C) countertransport with another molecule against its concentration gradient.
D) cotransport with another molecule against its concentration gradient.
E) a transporter that uses energy.

Question 55

Which of the following transport mechanisms requires energy?

A) primary active transport only
B) secondary active transport only
C) facilitated diffusion only
D) both primary and secondary active transport
E) both primary active transport and facilitated diffusion

Question 56

Which of the following transport mechanisms is passive?

A) transport of sodium and potassium across the membrane by the Na⁺/ K⁺ pump
B) cotransport of glucose with sodium
C) countertransport of hydrogen ions with sodium
D) movement of sodium through ion channels
E) movement of calcium out of the cytosol

Question 57

The hydrolysis of ATP on the Na⁺/ K⁺ pump results in

A) a conformational change that exposes the K⁺ binding site to the inside of the cell.
B) a conformational change that exposes the K⁺ binding site to the outside of the cell.
C) a conformational change that exposes the Na⁺ binding site to the inside of the cell.
D) a conformational change that exposes the Na⁺ binding site to the outside of the cell.
E) Na⁺ adhering to its binding site.

Question 58

If a cell becomes damaged and is temporarily unable to produce ATP, what is the likely outcome with respect to H₂O?

A) no change in water movement, as the anionic proteins lose their charge and can no longer create a membrane potential
B) dehydration, as water must be pumped in through aquaporins
C) cellular swelling, as water follows Na⁺ into the cell
D) dehydration, as water diffusion is a passive process
E) no change in water movement, as K⁺ is exchanged equally for Na⁺

Question 59

In facilitated diffusion, a molecule is moved

A) against its concentration gradient with the assistance of a protein carrier molecule and requires energy.
B) down its concentration gradient with the assistance of a protein carrier molecule, and no energy is required.
C) against its concentration gradient while Na is moved with its concentration gradient.
D) against its concentration gradient with the assistance of a protein carrier molecule, but no energy is required.
E) with its concentration gradient while Na is moved against its concentration gradient.

Question 60

In secondary active transport with sodium, which of the following is FALSE?

A) The molecule being transported moves down its electrochemical gradient.
B) Sodium binds to a carrier molecule, changing its binding properties for another molecule to be transported across the cell membrane.
C) Sodium always moves into the cell.
D) The molecule being transported into the cell may move in or out, depending on the carrier molecule.
E) ATP is necessary to produce an electrochemical gradient for sodium ions across the cell membrane.

Question 61

If solution 1 (0.1 M glucose and 0.15 M NaCl) and solution 2 (0.4 M glucose) are separated by a membrane, then solution 1 is

A) hypertonic
B) hypotonic
C) hyperosmotic
D) hypo -osmotic
E) iso -osmotic

Question 62

A cell with normal tonicity is placed in a 200 mM NaCl solution. This solution is and the cell will _.

A) isotonic : not change size
B) hypotonic : swell
C) hypertonic : swell
D) hypotonic : shrink
E) hypertonic : shrink

Question 63

The flow of water across a membrane down its concentration gradient is called

A) osmosis.
B) facilitated diffusion.
C) symporting.
D) leaking.
E) antiporting.

Question 64

Endocytosis is a form of active transport (requiring energy) to move vesicles

A) containing particles into and out of the cell, also known as phagocytosis.
B) containing proteins out of the cell, also known as secretion.
C) filled with particles and/or fluids out of the cell.
D) filled with particles and/or fluids into the cell.
E) containing fluids into and out of the cell, also known as pinocytosis.

Question 65

An erythrocyte is placed in a hypotonic solution of 100 mOsm. What will happen to the cell?

A) The cell swells to three times its original volume, Vf = 3Vo.
B) The cell shrinks to one half its original volume, Vf = 1/2 Vo.
C) The cell swells to twice its original volume, Vf = 2Vo.
D) The cell volume increases by one third, Vf = 4/3 Vo.
E) The cell volume remains unchanged.

Question 66

All of the following statements concerning severe hyperglycemia's effect on serum Na⁺ levels are true, EXCEPT

A) levels are measured as a concentration, so as water decreases, levels increase.
B) administering a hypertonic saline would help compensate for the decreased Na⁺ levels.
C) as insulin is administered, serum Na⁺ levels will return to normal.
D) the amount of Na⁺ is really unchanged since the water has only changed location and not left the body.
E) the Na⁺ levels would appear decreased as the ICF water leaves for the hyperosmotic ECF.

Question 67

Secretory vesicles are a part of what transport mechanism?

A) phagocytosis
B) pinocytosis
C) receptor -mediated endocytosis
D) osmosis
E) exocytosis

Question 68

The sodium -proton exchanger is an example of a(n)

A) cotransporter.
B) passive transporter.
C) primary active transporter.
D) antiporter.
E) symporter.

Question 69

The electrochemical gradient is to diffusion as

A) thermal energy
B) entropy
C) an ion channel
D) glucose
E) ATP

Question 70

The movement of a number of molecules across the apical surface of the epithelial cell by secondary transporters is coupled to the the basolateral surface of the epithelial cell.

A) K⁺ : K⁺ pump
B) K⁺ : K⁺ channel
C) Na⁺ : Na⁺ channel
D) Ca²⁺ : Na⁺/ K⁺ pump
E) Na⁺ : Na⁺/ K⁺ pump

Question 71

Epithelial cells are polarized with different structures at either end of the cell. The portion of the membrane that faces the lumen is called the _

A) basement
B) basolateral
C) abluminal
D) apical
E) transport

Question 72

If there is a difference in osmolarity between a cell and its environment, water will move its osmotic pressure gradient.

A) across
B) through
C) up
D) between
E) down

Question 73

A cell is placed into a solution that has the same osmolarity. However, one of the solutes in the solution is able to move across the membrane (the cell does not contain this solute). After a period of time, the solution into which the cell was placed would become

A) hyperosmotic.
B) isotonic.
C) hypertonic.
D) hypotonic.
E) iso -osmotic.

Question 74

White blood cells are an important component of our immune system. One thing they do is consume and destroy bacteria by extending their plasma membrane around the bacterium and bringing it inside the cell in a vesicle. By what process do they engulf the bacterium?

A) pinocytosis
B) phagocytosis
C) exocytosis
D) receptor -mediated endocytosis
E) transcytosis

Question 75

The osmotic pressure of a solution is a(n)

A) direct measure of its solvent concentration.
B) direct measure of its solute concentration.
C) indirect measure of its solute concentration.
D) indication of its glucose concentration.
E) indirect measure of its solvent concentration.

Question 76

A membrane permeable to water separates a chamber into two compartments: A and B. Compartment A contains a 10 mM solution of non -permeating solute, whereas compartment B contains a 40 mM solution of non -permeating solute. Which of the following statements is TRUE?

A) Solute will move from side A to B, and water will move from side B to A.
B) Solute will move from side B to A, and water will move from side A to B.
C) Water will move from side A to B, but solute will not move.
D) Both water and solute will move from side B to A.
E) Water will move from side B to A, but solute will not move.

Question 77

Vesicles formed during phagocytosis or endocytosis often fuse with the membrane of which of the following organelles?

A) smooth endoplasmic reticulum
B) peroxisome
C) lysosome
D) mitochondria
E) rough endoplasmic reticulum

Question 78

The extent of ion movement through the _ membrane.
Space between epithelial cells is determined by
The extent of coupling between neighboring epithelial cells.

A) transcellular : desmosomal
B) transcellular : gap junctional
C) transcellular : tight junctional
D) paracellular : tight junctional
E) paracellular : gap junctional

Question 79

If a solution contains 0.1 M glucose along with 0.15 M NaCl, what is the osmolarity of this solution?

A) 350 mOsm
B) 0.4 M
C) 0.25 M
D) 250 mOsm
E) 400 mOsm

Question 80

When white blood cells are called to an area of infection, not only is there phagocytosis taking place, but also exocytosis of undigested particles from the white blood cells into the interstitial space. What effect does this have on water in the surrounding cells and capillary plasma?

A) It creates a hypertonic environment, drawing water from the surrounding cells and plasma.
B) It dehydrates the area due to the increase in lysosomal waste products.
C) Swelling of the nearby cells and plasma ensues due to the hypotonic nature of the area.
D) These particles have no effect on tonicity, since their precursors were already in the body.
E) Plasma water moves to the interstitium by osmosis and then into the adjacent cells.