1. The plasma membrane of liver cells contains a glucose uniportthat transports glucose by facilitated diffusion. When the[glucose] is higher inside the liver cell than the [glucose]outside the liver cell, the glucose uniport will
A. couple the transport of glucose out of the cell to thehydrolysis of ATP
B. couple the transport of glucose into the cell to thehydrolysis of ATP
C. switch to a closed conformation, allowing no transport ofglucose
D. transport glucose out of the cell by passive transport
E. transport glucose in of the cell by passive transport
2. Unlike the positive charged ion shown in the middle diagramof figure 11-4B, K+ is higher in concentration inside the cell. Howwill the membrane potential of a cell at rest (shown in both themiddle and right-hand diagrams of Figure 11-4B) affect theelectrochemical gradient for K+?
A. The membrane potential will increase the electrochemicalgradient
B. The membrane potential will decrease the electrochemicalgradient
C. The membrane potential will have no effect on theelectrochemical gradient
3. Which of the following proteins carries out activetransport?
A. gluclose symport
B. Bacteriorhodopsin
C. ABC transporter
D. NA K pump
E. All of the above
4. Aquaporin will not transport Na+ ions because
A. Two asparagine residues in the channel prevent the passage ofNa+ ions by binding the oxygen of each water molecule as it passesby
B. Na+ ions are repelled by the positive charges at the entranceto the channel
C. Na+ ions cannot make contact with the carbonyl (C=O) groupson all four sides of the channel
D. The passage of Na+ ions is energetically unfavorable becauseone side of the channel is hydrophobic in nature
5. The acetylcholine receptor is different from other channelproteins we have discussed, such as the K+ leak channel,because
A. The acetylcholine channel is composed of a single polypeptiderather than multiple subunits
B. The acetylcholine channel transports Na+ ions against theconcentration gradient for sodium
C. The acetylcholine channel has a much smaller diameter thanother channel proteins
D. The acetylcholine channel transports ions with theirassociated shell of water molecules
E. The acetylcholine channel is always open, and never switchesto a closed conformation
6. After opening briefly along the axon of a neuron,voltage-gated ion channels switch to an inactivated conformationthat slowly returns to the original closed conformation of theprotein. This slow change in conformation, requiring about amillisecond, is important because
A. all of the ions that were transported across the membranewhen the ion channels were open must be actively transported backto the other side of the membrane, restoring the originalconcentration gradient, before the ion channels can open again
B. ATP hydrolysis is necessary to drive this energeticallyunfavorable change in conformation
C. it prevents the action potential from reversing direction andtraveling back toward the cell body of the neuron
D. the channel protein must be dephosphorylated in order tocomplete the transport process and return to the originalnonphosphorylated conformation
