Question 1

ABC-type ATPases that inhibit the effectiveness of antitumor drugs by transporting the drugs out of tumor cells are known as

Accepted Answer

A)  multidrug resistance (MDR) transporters.
B)  Na+-drug antiporters.
C)  the cystic fibrosis transmembrane conductance regulator (CFTR) .
D)  porins.
E)  None of the above; no such transporter has been identified in eukaryotes. A

Question 2

The bacterium Brucella abortus imports and uses the unusual sugar erythritol.The concentration of erythritol within the B.abortus cell is 10 mM,but the external erythritol concentration is much lower at 0.20 mM.What is the energy requirement (ΔG _inward in kcal/mol)for the inward transport of erythritol at 37°C under these conditions?

Accepted Answer

Use the equation ΔG _inward= RT ln[S] inside/[S] outside.With the gas constant R = 1.987 cal/mol-K,the absolute temperature T in Kelvin = (°C + 273),[S] inside = 10 mM and [S] outside = 0.2 mM,the above equation becomes: ΔG _inward = (1.987 cal/mol-K)(37 + 273 K)ln(10 mM/0.2 mM)= 615.97 ln 50 = 2409.69 cal/mol = +2.41 kcal/mol (Note: this value is positive,because the transport is against the concentration gradient.)

Question 3

The primary difference between active transport and facilitated diffusion is that active transport is the only one of the two in which

Accepted Answer

A)  transporter proteins are required.
B)  the direction of transport is [S]high → [S]low.
C)  the direction of transport is [S]low → [S]high.
D)  the S concentration gradient provides the energy necessary for S transport.
E)  the mechanism is not saturable. C

Question 4

Cystic fibrosis is the result of a malfunction of a cellular ABC transporter that transports

Accepted Answer

A)  Cl−.
B)  amino acids.
C)  vitamin B12.
D)  glucose.
E)  a hydrophobic drug.

Question 5

What is the mechanism by which expression of an MDR protein affects treatment of cancer cells with an antitumor drug? How might you potentially counter the effect of such transporters?

Accepted Answer

The answer of What is the mechanism by which expression...

Question 6

Whereas animal cells drive indirect transport with a Na+ gradient,most other organisms use

Accepted Answer

A)  a glucose gradient.
B)  light energy.
C)  an H+ gradient.
D)  a Ca2+ gradient.
E)  osmosis.

Question 7

What specific type of P-type ATPase pumps H+ to acidify the stomach and is inhibited by proton pump inhibitor drugs used to treat excess stomach acid?

Accepted Answer

A)  type 1
B)  type 2
C)  type 3
D)  type 4
E)  type 5

Question 8

Mutations in bacterial porins typically lead to antibiotic resistance by

Accepted Answer

A)  changing the orientation of the porin α-helical transmembrane segments to constrict the size of the channel.
B)  changing the stereoisomer specificity of the porin transport.
C)  blocking diffusion of the antibiotic through the porin channel.
D)  disrupting the voltage difference across the porin channel.
E)  reversing water transport through the channel.

Question 9

The type of transport ATPase that is reversibly phosphorylated as part of the transport mechanism is the ________ ATPase.

Accepted Answer

The answer of The type of transport ATPase that is...

Question 10

Simultaneous transport of two molecules across the cell membrane in the same direction by one transporter is called ________.

Accepted Answer

The answer of Simultaneous transport of two molecules across the...

Question 11

Although all P-type ATPases use the energy of ATP hydrolysis to transport solutes they differ in which of the following?

Accepted Answer

A)  structure
B)  mechanism
C)  localization in cells
D)  physiological roles
E)  All of the above are correct.

Question 12

Frog oocytes are a useful experimental system for studying transporters,because frog oocytes possess all of the following characteristics except

Accepted Answer

A)  they are large,easily injected cells.
B)  they express all transporters known.
C)  they express injected heterologous mRNAs.
D)  they are relatively inexpensive and easy to obtain.
E)  they can be maintained in little more than pure water.

Question 13

The transport of two molecules across the cell membrane in different directions by one transporter is called ________.

Accepted Answer

The answer of The transport of two molecules across the...

Question 14

Which type of P-type ATPase would you expect to find is defective in a novel cell line in which you observe that maintenance of the phospholipid asymmetry in the plasma membrane is impaired?

Accepted Answer

A)  type 1
B)  type 2
C)  type 3
D)  type 4
E)  type 5

Question 15

Bacterial porins transport

Accepted Answer

A)  any hydrophilic molecule regardless of size.
B)  hydrophilic molecules smaller than 600 Da.
C)  any hydrophobic molecule regardless of size.
D)  hydrophobic molecules larger than 600 Da.
E)  any molecule regardless of properties or size.

Question 16

Phosphorylation of glucose following its transport into a cell

Accepted Answer

A)  targets the glucose for transport back out of the cell.
B)  decreases glucose transport into the cell by decreasing its concentration gradient across the plasma membrane.
C)  increases glucose transport into the cell by increasing its concentration gradient across the plasma membrane.
D)  converts glucose into a form that can more easily be exported from the cell.
E)  maintains a higher level of glucose outside the cell.

Question 17

Each of the following is a characteristic of active transport mechanisms except

Accepted Answer

A)  sensitivity to inhibitors such as proton pump inhibitors.
B)  nondirectionality for moving a solute in either direction across a membrane depending on the solute concentration gradient.
C)  coupling transport of a solute down its concentration with transport of another solute up its concentration gradient via a symport or antiport mechanism..
D)  moving solutes away from equilibrium across a membrane.
E)  coupling a thermodynamically unfavorable (endergonic) process with a favorable (exergonic) process.

Question 18

Gated ion channels include each of the following except

Accepted Answer

A)  voltage-gated channels.
B)  ligand-gated channels.
C)  mechanosensitive channels.
D)  patch clamp-gated channels.
E)  All of the above are types of gated channels.

Question 19

Which of the following is an example of indirect active transport?

Accepted Answer

A)  Na+/K+ ATPase
B)  aquaporin water transport
C)  CFTR Cl− transport
D)  Na+/glucose symport
E)  glucose permease transport

Question 20

Each of the following is an example of facilitated diffusion except

Accepted Answer

A)  glucose transport by GLUT1.
B)  chloride-bicarbonate exchange.
C)  aquaporin transport.
D)  ion channel transport.
E)  oxygen transport.

Exam 8: Transport Across Membranes: Overcoming the Permeability Barrier