Ch.9 Ion Transport Across Cell Membranes Exam Prep

Chapter 9: Ion Transport Across Cell Membranes

Test Bank

Type: multiple choice question

Title: Chapter 09 - Question 01

1. Unlike secondary active transport, primary active transport

Feedback: Subhead: The Sodium–Potassium Exchange Pump

Learning Objective: Differentiate between primary active transport and secondary active transport.

Bloom’s Level: 2. Understanding

a. relies on the movement of sodium down its electrochemical gradient.

b. is exemplified by sodium-calcium exchange.

c. is reversible.

d. depends on sodium–potassium ATPase.

e. uses energy provided by hydrolysis of ATP.

Type: multiple choice question

Title: Chapter 09 - Question 02

2. In the absence of transport mechanisms, ions would only move across the membrane along their electrochemical gradient. What consequences would this have?

Feedback: Subhead: The Sodium–Potassium Exchange Pump

Learning Objective: Explain why the sodium–potassium exchange pump is needed to maintain cell viability.

Bloom’s Level: 3. Applying

a. The concentration gradients and the potential across the cell membrane would disappear.

b. The concentration gradients across the membrane would be recovered through passive mechanisms relying on Donnan equilibrium.

c. The resting membrane potential of the cells would become more hyperpolarized.

d. Neurons would continuously fire action potentials.

e. Astrocytes, not neurons, would rest at 0 mV.

Type: multiple choice question

Title: Chapter 09 - Question 03

3. What drives primary active transport?

Feedback: Subhead: The Sodium–Potassium Exchange Pump

Learning Objective: State what the source of energy is for the sodium–potassium exchange pump.

Bloom’s Level: 2. Understanding

a. Ion exchange

b. Sodium

c. Potassium

d. Water

e. The hydrolysis of ATP

Type: multiple choice question

Title: Chapter 09 - Question 04

4. What drives secondary active transport?

Feedback: Subhead: The Sodium–Potassium Exchange Pump

Learning Objective: State what the source of energy is for the sodium–potassium exchange pump.

Bloom’s Level: 1. Remembering

a. Metabolic energy

b. ATP

c. Ion flux down their electrochemical gradient

d. Osmotic pressure

e. Diffusion

Type: multiple choice question

Title: Chapter 09 - Question 05

5. Why is the sodium–potassium exchange pump said to be electrogenic?

Feedback: Subhead: The Sodium–Potassium Exchange Pump

Learning Objective: Explain why the sodium–potassium exchange pump is said to be electrogenic.

Bloom’s Level: 4. Analyzing

a. Because it transports the same number of positively charged ions in and out of the cell membrane

b. Because it transports unequal numbers of sodium and potassium ions across the membrane

c. Because ion binding requires a change in membrane potential

d. Because ion transport can only be triggered by electrical stimuli

e. Because it has an electroneutral stoichiometry

Type: multiple choice question

Title: Chapter 09 - Question 06

6. What is the first event for ion transport through the sodium–potassium exchange pump?

Feedback: Subhead: The Sodium–Potassium Exchange Pump

Learning Objective: Describe the general sequence of events that occur when sodium and potassium ions are translocated.

Bloom’s Level: 1. Remembering

a. Sodium binding to the inward-facing sites of the pump

b. Potassium binding to the inward-facing sites of the pump

c. Potassium binding to the outward-facing sites of the pump

d. ATP hydrolysis

e. ATP phosphorylation

Type: multiple choice question

Title: Chapter 09 - Question 07

7. How does the sequence of events underlying ion transport through the sodium–potassium exchange pump end?

Feedback: Subhead: The Sodium–Potassium Exchange Pump

Learning Objective: Describe the general sequence of events that occur when sodium and potassium ions are translocated.

Bloom’s Level: 1. Remembering

a. Dephosphorylation of the pump

b. Binding of sodium ions

c. Intracellular binding of potassium ions

d. Release of potassium ions into the cytoplasm

e. Opening of an aqueous pore in the protein

Type: multiple choice question

Title: Chapter 09 - Question 08

8. How does rise in intracellular sodium concentration affect the resting membrane potential through the activity of the sodium–potassium exchange pump?

Feedback: Subhead: The Sodium–Potassium Exchange Pump

Learning Objective: Describe the general sequence of events that occur when sodium and potassium ions are translocated.

Bloom’s Level: 5. Evaluating

a. It would trigger membrane depolarization.

b. It would not lead to significant changes in the resting membrane potential.

c. It would trigger membrane hyperpolarization.

d. It would change the stoichiometry of the transport process.

e. It would promote phosphorylation and desphosphorylation of the pump, which would make the cell membrane leakier.

Type: multiple choice question

Title: Chapter 09 - Question 09

9. What is one of the main functional consequences of increasing cytoplasmic levels of calcium in muscle fibers?

Feedback: Subhead: Calcium Pumps

Learning Objective: Give two examples of how changes in intracellular calcium affect neuronal function.

Bloom’s Level: 3. Applying

a. Trigger muscle relaxation

b. Prevent acetylcholine receptor activation

c. Inhibit action potential propagation

d. Speed up action potential propagation

e. Initiate muscle contraction

Type: multiple choice question

Title: Chapter 09 - Question 10

10. What is one of the main functional consequences of increasing cytoplasmic levels of calcium in neurons?

Feedback: Subhead: Calcium Pumps

Learning Objective: Give two examples of how changes in intracellular calcium affect neuronal function.

Bloom’s Level: 5. Evaluating

a. Promote neurotransmitter release

b. Hyperpolarize the resting membrane potential

c. Change the membrane capacitance

d. Depolarize the threshold for action potential initiation

e. Change the driving force for sodium ions

Type: multiple choice question

Title: Chapter 09 - Question 11

11. Which intracellular organelles contribute to return the intracellular calcium concentration to its resting levels?

Feedback: Subhead: Calcium Pumps

Learning Objective: Give two examples of how changes in intracellular calcium affect neuronal function.

Bloom’s Level: 2. Understanding

a. Golgi apparatus and cell nucleus

b. Lysosomes and synaptic vesicles

c. Endoplasmic reticulum and cell nucleus

d. Endoplasmic/sarcoplasmic reticulum and mitochondria

e. Mitochondria and lysosomes

Type: multiple choice question

Title: Chapter 09 - Question 12

12. There are _______ classes or families of calcium ATPases.

Feedback: Subhead: Calcium Pumps

Learning Objective: Name the two classes of calcium ATPases and explain how they maintain calcium concentration in the cytoplasm at the appropriate level.

Bloom’s Level: 2. Understanding

a. 2

b. 3

c. 4

d. 5

e. 10

Type: multiple choice question

Title: Chapter 09 - Question 13

13. Why is the recovery of intracellular calcium concentration after calcium influx not influenced by membrane potential?

Feedback: Subhead: Calcium Pumps

Learning Objective: Name the two classes of calcium ATPases and explain how they maintain calcium concentration in the cytoplasm at the appropriate level.

Bloom’s Level: 5. Evaluating

a. Because the transport cycle of the plasma cell membrane calcium ATPase is electrogenic

b. Because the plasma cell membrane calcium ATPase has a high affinity for calcium

c. Because calcium binding to the plasma cell membrane calcium ATPase is voltage-dependent

d. Because the transport cycle of the plasma cell membrane calcium ATPase is electroneutral

e. Because the plasma cell membrane calcium ATPase has a low transport capacity

Type: multiple choice question

Title: Chapter 09 - Question 14

14. How does the calcium transport cycle via the calcium ATPase begin?

Feedback: Subhead: Calcium Pumps

Learning Objective: Name the two classes of calcium ATPases and explain how they maintain calcium concentration in the cytoplasm at the appropriate level.

Bloom’s Level: 2. Understanding

a. It begins with the attachment of two calcium ions to cytoplasmic binding sites.

b. It begins with the attachment of two protons to extracellular binding sites.

c. It begins with the hydrolysis of ATP.

d. It begins with opening of a channel pore.

e. It begins with calcium binding to the extracellular side of the calcium ATPase.

Type: multiple choice question

Title: Chapter 09 - Question 15

15. What is the stoichiometry of the NCX transport system?

Feedback: Subhead: The Sodium–Calcium Exchange

Learning Objective: Explain how sodium can provide the energy to carry other ions uphill against their electrochemical gradients.

Bloom’s Level: 1. Remembering

a. Two potassium ions outward for every three sodium ions entering the cell (3 Na⁺:2K⁺)

b. Two calcium ions outward for every two protons entering the cell (2 H⁺:2 Ca²⁺)

c. One calcium ion outward for every three sodium ions entering the cell (3 Na⁺:1 Ca²⁺)

d. One ion X outward for every one sodium and one calcium ions entering the cell (1Na⁺:1 Ca²⁺:1 X)

e. Na⁺ and Ca²⁺ are not transported in a fixed ratio through the NCX transport system

Type: multiple choice question

Title: Chapter 09 - Question 16

16. How does reducing the extracellular sodium concentration increase the intracellular calcium concentration?

Feedback: Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium can provide the energy to carry other ions uphill against their electrochemical gradients.

Bloom’s Level: 4. Analyzing

a. By increasing passive calcium influx through the cell membrane

b. By reducing the activity of the NCX transport system

c. By hyperpolarizing the resting membrane potential

d. By inverting the electrochemical gradient for calcium

e. By inhibiting the activity of the Na⁺/K⁺ ATPase

Type: multiple choice question

Title: Chapter 09 - Question 17

17. How can ion exchange mechanisms be made to run backwards?

Feedback: Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium can provide the energy to carry other ions uphill against their electrochemical gradients.

Bloom’s Level: 4. Analyzing

a. By altering one or more of the ion gradient involved in the exchange

b. By inhibiting ATP hydrolysis

c. By hyperpolarizing the resting membrane potential

d. By replacing extracellular sodium with lithium

e. By removing calcium from the extracellular solution

Type: multiple choice question

Title: Chapter 09 - Question 18

18. How can you calculate the energy dissipated by sodium entry through the NCX transport system?

Feedback: Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium can provide the energy to carry other ions uphill against their electrochemical gradients.

Bloom’s Level: 4. Analyzing

a. By dividing the sum of all charges moved across the NCX transport system by their driving force

b. By subtracting the resting membrane potential from the equilibrium potential for sodium

c. By calculating the equilibrium potential for sodium

d. By analyzing the 3D crystal structure of the NCX transport system

e. By multiplying the charge moved across the membrane by the driving force for this movement

Type: multiple choice question

Title: Chapter 09 - Question 19

19. When does the NCX stop moving ions across the membrane?

Feedback: Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium can provide the energy to carry other ions uphill against their electrochemical gradients.

Bloom’s Level: 2. Understanding

a. When the energy dissipated by sodium entry equals that associated with movement of calcium ions

b. When the resting membrane potential equals the reversal potential for calcium

c. When the driving force for sodium is different than 0 mV

d. When there is no net driving force for calcium

e. When there is not ATP

Type: multiple choice question

Title: Chapter 09 - Question 20

20. How does the NCKX system differ from the NCX system?

Feedback: Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium–calcium exchange in retinal rods differs from that in most other neurons.

Bloom’s Level: 1. Remembering

a. The NCX system is only expressed in the outer segment of vertebrate retinal rod cells.

b. The NCKX system is only expressed in muscle fibers.

c. The NCKX system is expressed in the plasma cell membrane, whereas the NCX system is expressed in the sarcoplasmic and endoplasmic reticulum and in mitochondria.

d. In addition to transporting sodium and calcium, NCKX transports potassium.

e. The NCKX system is a primary active transport mechanism, whereas the NCX system is a secondary active transport mechanism.

Type: multiple choice question

Title: Chapter 09 - Question 21

21. What is the stoichiometry of the NCKX transport system?

Feedback: Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium–calcium exchange in retinal rods differs from that in most other neurons.

Bloom’s Level: 1. Remembering

a. One calcium and one potassium ion outward for every four sodium ions entering the cell (4 Na⁺:1 Ca²⁺:1K⁺)

b. Three potassium ions outward for every three sodium ions and one calcium entering the cell (3 Na⁺:1 Ca²⁺:3K⁺)

c. Two calcium ions outward for every two protons and one potassium entering the cell (2 H⁺:2 Ca²⁺:1K⁺)

d. One ion X outward for every one sodium, one potassium and one calcium ions entering the cell (1Na⁺:1 Ca²⁺:1K⁺:1 X)

e. Na⁺, K⁺ and Ca²⁺ are not transported in a fixed ratio through the NCX transport system

Type: multiple choice question

Title: Chapter 09 - Question 22

22. Why is the regulation of intracellular chloride important in neurons?

Feedback: Subhead: Chloride Transport

Learning Objective: Explain why the regulation of intracellular chloride is particularly important in neurons.

Bloom’s Level: 5. Evaluating

a. Because it can change the threshold for action potential initiation

b. Because it determines the magnitude of synaptic excitation

c. Because it determines the polarity of synaptic inhibition

d. Because it controls the production of ATP

e. Because it has implications for calcium homeostasis

Type: multiple choice question

Title: Chapter 09 - Question 23

23. What supplies the energy required for the inward chloride transport across the plasma cell membrane?

Feedback: Subhead: Chloride Transport

Learning Objective: Discuss the two major transport mechanisms for chloride.

Bloom’s Level: 1. Remembering

a. The movement of potassium down its concentration gradient

b. The movement of sodium down its concentration gradient

c. ATP hydrolysis

d. The Na⁺/K⁺ ATPase

e. The sodium–calcium exchanger

Type: multiple choice question

Title: Chapter 09 - Question 24

24. What supplies the energy required for outward chloride transport across the plasma cell membrane?

Feedback: Subhead: Chloride Transport

Learning Objective: Discuss the two major transport mechanisms for chloride.

Bloom’s Level: 1. Remembering

a. The movement of potassium down its concentration gradient

b. The movement of sodium down its concentration gradient

c. ATP hydrolysis

d. The Na⁺/K⁺ ATPase

e. The sodium–calcium exchanger

Type: multiple choice question

Title: Chapter 09 - Question 25

25. Which transporters are blocked by furosemide and bumetanide?

Feedback: Subhead: Chloride Transport

Learning Objective: Discuss the two major transport mechanisms for chloride.

Bloom’s Level: 2. Understanding

a. The chloride–bicarbonate exchanger

b. The NCX and NKCX systems

c. Vesicular transporters for the neurotransmitter glutamate

d. Plasma cell membrane transporters for the neurotransmitter glutamate

e. The inward chloride and outward potassium–chloride transporters

Type: multiple choice question

Title: Chapter 09 - Question 26

26. What is the main function of chloride–bicarbonate exchangers?

Feedback: Subhead: Chloride Transport

Learning Objective: Name the primary function served by chloride–bicarbonate exchange systems.

Bloom’s Level: 2. Understanding

a. Regulate cell volume

b. Maintain cells at their resting membrane potential

c. Regulate intracellular pH

d. Determine the polarity of synaptic inhibition

e. Determine the polarity of synaptic excitation

Type: multiple choice question

Title: Chapter 09 - Question 27

27. Where are neurotransmitters synthesized?

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are transported from their site of synthesis into synaptic vesicles.

Bloom’s Level: 2. Understanding

a. Nucleus

b. Endoplasmic and sarcoplasmic reticulum

c. Cytoplasm

d. Mitochondria

e. Golgi apparatus

Type: multiple choice question

Title: Chapter 09 - Question 28

28. Where are neurotransmitters stored?

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are transported from their site of synthesis into synaptic vesicles.

Bloom’s Level: 2. Understanding

a. Synaptic vesicles

b. Glial cells

c. Dendrites

d. Soma

e. Axon initial segment

Type: multiple choice question

Title: Chapter 09 - Question 29

29. Each of these is a vesicular neurotransmitter transporter except

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are transported from their site of synthesis into synaptic vesicles.

Bloom’s Level: 1. Remembering

a. VMAT.

b. VAChT.

c. VGAT.

d. GAT.

e. VGLUT.

Type: multiple choice question

Title: Chapter 09 - Question 30

30. Which ion, in addition to protons, is cotransported into synaptic vesicles together with glutamate?

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are transported from their site of synthesis into synaptic vesicles.

Bloom’s Level: 1. Remembering

a. Sodium

b. Chloride

c. Potassium

d. Calcium

e. GABA

Type: multiple choice question

Title: Chapter 09 - Question 31

31. What is one of the main functional deficits of VGLUT3 knockout mice?

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are recovered after their release.

Bloom’s Level: 4. Analyzing

a. Deafness

b. Blindness

c. Ataxia

d. Epilepsy

e. Migraine

Type: multiple choice question

Title: Chapter 09 - Question 32

32. Which of the following is a GABA transporter mostly expressed in neurons?

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are recovered after their release.

Bloom’s Level: 1. Remembering

a. GAT1

b. GAT3

c. GLAST

d. DAT

e. NET

Type: multiple choice question

Title: Chapter 09 - Question 33

33. How is ACh recycled into presynaptic terminals?

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are recovered after their release.

Bloom’s Level: 2. Understanding

a. Through the activity of VChAT

b. Through monoamine transporters

c. Through glutamate transporters

d. Through GABA transporters

e. ACh is not recycled into presynaptic terminals.

Type: multiple choice question

Title: Chapter 09 - Question 34

34. How does reversed glutamate uptake affect brain function after brain damage by stroke or trauma?

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are recovered after their release.

Bloom’s Level: 5. Evaluating

a. By preventing glutamate receptor activation

b. By promoting glutamate uptake in presynaptic terminals

c. By promoting glial cell death

d. By triggering excitotoxicity in the damaged area

e. Glutamate transporters can only transport glutamate towards the cell cytoplasm, not into the extracellular space.

Type: multiple choice question

Title: Chapter 09 - Question 35

35. What unique feature distinguishes GLYT2 glycine transporters from other members of the SLC6 family?

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are recovered after their release.

Bloom’s Level: 2. Understanding

a. It is only expressed in neurons.

b. It is only expressed in presynaptic terminals.

c. Its transport stoichiometry is three sodium to one chloride to one glycine.

d. It is only expressed in postsynaptic terminals.

e. It is only expressed extrasynaptically.

Type: multiple choice question

Title: Chapter 09 - Question 36

36. What are two purposes served by the recovery of neurotransmitters?

Feedback: Subhead: Transport of Neurotransmitters

Learning Objective: Name two purposes served by the recovery of neurotransmitter.

Bloom’s Level: 5. Evaluating

a. 1) store neurotransmitter into synaptic vesicles; 2) promote neurotransmitter diffusion into glial cells

b. 1) trigger reversed uptake; 2) restore ionic gradients across the membrane

c. 1) dissipate ionic gradients across the membrane; 2) promote neurotransmitter degradation

d. 1) inhibit further neurotransmitter release; 2) promote excitotoxicity

e. 1) prevent neurotransmitter diffusion out of the synaptic cleft; 2) recover neurotransmitter molecules for release

Type: multiple choice question

Title: Chapter 09 - Question 37

37.What are the α- and β-subunits of the sodium–potassium ATP responsible for?

Feedback: Subhead: Molecular Structure of Transporters

Learning Objective: Describe the molecular structure of ATPases and sodium–calcium exchangers.

Bloom’s Level: 1. Remembering

a. The α-subunit is responsible for binding sodium ions. The β-subunit is responsible for binding potassium ions.

b. The α-subunit is responsible for the enzymatic activity of the pump and contains all the substrate-binding sites. The β-subunit has several extracellular glycosylation sites and is necessary for pump function.

c. The α-subunit is responsible for binding sodium and potassium ions. The β-subunit is the substrate of phosphorylation.

d. The α-subunit is not necessary for pump function. The β-subunit contains binding sites for sodium, potassium and ATP.

e. The sodium–potassium ATPase consists of a single polypeptide chain without a β-subunit.

Type: multiple choice question

Title: Chapter 09 - Question 38

38. Which experimental approach has been used to determine the molecular structure of the sarcoplasmic and endoplasmic reticulum calcium ATPase?

Feedback: Subhead: Molecular Structure of Transporters

Learning Objective: Describe the molecular structure of ATPases and sodium–calcium exchangers.

Bloom’s Level: 4. Analyzing

a. Electrophysiology

b. Cloning

c. Computer modeling

d. X-ray crystallography

e. Genetic screening

Type: multiple choice question

Title: Chapter 09 - Question 39

39. Which sodium–calcium exchangers have the shortest amino acidic sequence?

Feedback: Subhead: Molecular Structure of Transporters

Learning Objective: Describe the molecular structure of ATPases and sodium–calcium exchangers.

Bloom’s Level: 1. Remembering

a. NCKX1

b. NCX1

c. NCKX2-4

d. NCX2-3

e. All exchangers have the same amino acid sequence length

Type: multiple choice question

Title: Chapter 09 - Question 40

40. Which bacterial homologs have been used in crystallography studies to determine key structural features of eukaryotic neurotransmitter transporters?

Feedback: Subhead: Molecular Structure of Transporters

Learning Objective: Describe the molecular structure of ATPases and sodium–calcium exchangers.

Bloom’s Level: 1. Remembering

a. LeuT_Aa and Glt_Ph

b. GAT and GLYT

c. NET and SERT

d. DAT and GAT

e. VMAT and VAChT

Type: multiple choice question

Title: Chapter 09 - Question 41

41. Which chloride transporter is transiently expressed in the immature brain?

Feedback: Subhead: Significance of Transport Mechanisms

Learning Objective: Give two examples of how ion transport molecules play an active role in cell signaling.

Bloom’s Level: 1. Remembering

a. KCC2

b. NKCC1

c. NCX

d. NKCX

e. GLAST

Type: multiple choice question

Title: Chapter 09 - Question 42

42. How do developmental changes in chloride transporter expression affect GABAergic transmission?

Feedback: Subhead: Significance of Transport Mechanisms

Learning Objective: Give two examples of how ion transport molecules play an active role in cell signaling.

Bloom’s Level: 5. Evaluating

a. The developmental switch from NKCC1 to KCC2 allows GABA to become depolarizing.

b. Changes in chloride transporter expression do not alter GABAergic transmission.

c. In the immature brain, GABA transporters can transport both glutamate and GABA. The delayed expression of KCC2 promotes the substrate specificity of GABA transporters.

d. Developmental changes in chloride transporters allow GABAergic transmission to have faster kinetics.

e. The delayed expression of KCC2 allows GABA to evoke membrane hyperpolarization in the mature, not the immature brain.

Type: multiple choice question

Title: Chapter 09 - Question 43

43. Which of the following transporters is the target of fluoexitine (Prozac), used in the treatment of psychiatric disorders such as depression and anxiety?

Feedback: Subhead: Significance of Transport Mechanisms

Learning Objective: Give two examples of how ion transport molecules play an active role in cell signaling.

Bloom’s Level: 1. Remembering

a. Monoamine transporters

b. GABA transporters

c. Glutamate transporters

d. Sodium–calcium exchangers

e. Vesicular transporters

Type: essay/short answer question

Title: Chapter 09 - Question 44

44. Summarize the difference between primary active transport and secondary active transport.
Feedback: Primary active transport is driven primarily by metabolic energy, produced by the hydrolysis of ATP. Secondary active transport uses energy provided by the flux of an ion, usually the result of sodium moving down its electrochemical gradient to transport other ions across the membrane.
Subhead: The Sodium–Potassium Exchange Pump

Learning Objective: Differentiate between primary active transport and secondary active transport.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 09 - Question 45

45. Given that the sodium–potassium pump is electrogenic, how do you think intracellular injection of sodium would change the membrane potential of a neuron?

Feedback: As shown by Thomas, a brief intracellular injection of sodium would lead to a transient membrane hyperpolarization because of increased pump activity. The potential recovered gradually over several minutes, as the excess sodium was extruded.

Subhead: The Sodium–Potassium Exchange Pump.

Learning Objective: Explain why the sodium–potassium exchange pump is needed to maintain cell viability.

Bloom’s Level: 4. Analyzing

Type: essay/short answer question

Title: Chapter 09 - Question 46

46. What makes transporters electrogenic?

Feedback: Their ability to transport unequal numbers of ions across the membrane. Therefore, each transport cycle results in the net inward or outward movement of positive charges across the membrane.

Subhead: The Sodium–Potassium Exchange Pump.

Learning Objective: Explain why the sodium–potassium exchange pump is said to be electrogenic.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 09 - Question 47

47. Where are calcium pumps located in a cell?

Feedback: There are calcium pumps located in the plasma cell membrane, as well as in the endoplasmic and sarcoplasmic reticulum. All these pumps act in concert to keep the cytoplasmic concentration of calcium at low levels.

Subhead: Calcium Pumps

Learning Objective: Give two examples of how changes in intracellular calcium affect neuronal function.

Bloom’s Level: 2. Understanding.

Type: essay/short answer question

Title: Chapter 09 - Question 48

48. Which fundamental feature distinguishes plasma membrane from endoplasmic and sarcoplasmic reticulum calcium ATPases?

Feedback: The stoichiometry of the transport process. The calcium transport cycle of the endoplasmic and sarcoplasmic reticulum calcium ATPase relies on the translocation of two calcium ions across the membrane and is therefore electrogenic. The calcium transport cycle of the plasma cell membrane calcium ATPase relies on the counter transport of one calcium ion and two protons across the membrane and is therefore electroneutral.

Subhead: Calcium Pumps

Learning Objective: Name the two classes of calcium ATPases and explain how they maintain calcium concentration in the cytoplasm at the appropriate level.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 09 - Question 49

49. Why is the overall transport capacity of the NCX transport system, despite having a lower affinity for calcium, 50 times greater than that of the calcium ATPase?

Feedback: Because the NCX molecules are expressed at a much higher density than calcium ATPases. The exchange system is called into play in excitable cells when calcium influx during electrical activity overwhelms the transport ability of the ATPase.

Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium can provide the energy to carry other ions uphill against their electrochemical gradients.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 09 - Question 50

50. How can the ion exchange mechanism of the NCX transport system be made to run backward?

Feedback: By altering one or more of the ion gradients involved in the exchange process. The direction of transport is determined simply by whether the energy provided by the entry of three sodium ions is greater than or less than the energy required to extrude one calcium ion. Forward transport is facilitated by membrane hyperpolarization and impeded, or even reversed, by depolarization.

Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium can provide the energy to carry other ions uphill against their electrochemical gradients.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 09 - Question 51

51. How can you calculate the energy dissipated by sodium entry via the NCX transport system?

Feedback: By multiplying, the charge moved across the membrane and the driving force for this movement. This, for the NCX transport system, corresponds to 3(E_Na-V_r).

Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium can provide the energy to carry other ions uphill against their electrochemical gradients.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 09 - Question 52

52. How does the NCX transport system in vertebrate retinal rods differ from that expressed in other cell types?

Feedback: The calcium extrusion system in vertebrate retinal rods, known as NCKX, has a different transport stoichiometry compared to the NCX transport system. In addition to transporting sodium and calcium, the NCKX transports potassium. Because of this, NCKX is unlikely to reverse at depolarized potentials.

Subhead: Sodium–Calcium Exchange

Learning Objective: Explain how sodium–calcium exchange in retinal rods differs from that in most other neurons.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 09 - Question 53

53. Why is the regulation of intracellular chloride concentration important in neurons?

Feedback: Because, by regulating the electrochemical gradient for chloride, it determines whether GABAergic transmission via ionotropic receptors is hyperpolarizing, shunting or depolarizing.

Subhead: Chloride Transport

Learning Objective: Explain why the regulation of intracellular chloride is particularly important in neurons.

Bloom’s Level: 4. Analyzing

Type: essay/short answer question

Title: Chapter 09 - Question 54

54. Why is GABA depolarizing in the immature brain?

Feedback: Because the main chloride transporter expressed in the immature brain, NKCC1, accumulates sodium in the cell cytoplasm. This makes the equilibrium potential for chloride depolarized. Consequently, the activation of chloride permeable GABA_A receptors leads to membrane depolarization.

Subhead: Chloride Transport

Learning Objective: Explain why the regulation of intracellular chloride is particularly important in neurons.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 09 - Question 55

55. What is the main function of chloride-bicarbonate exchangers?

Feedback: Chloride–bicarbonate exchangers, together with sodium–hydrogen exchange, serve primarily to regulate intracellular pH. Quantitatively, the role of this system is minimal in regulating intracellular chloride concentration in excitable cells.

Subhead: Chloride Transport

Learning Objective: Name the primary function served by chloride–bicarbonate exchange systems.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 09 - Question 56

56. Which ionic gradients commonly drive neurotransmitter uptake into synaptic vesicles and in the cell cytoplasm?

Feedback: Neurotransmitter transport into synaptic vesicles is typically driven by a proton gradient established by the transport of protons from the cytoplasm into the vesicle by hydrogen ATPase. Neurotransmitter transport from the extracellular space into the cell cytoplasm is typically driven by the electrochemical gradient for sodium.

Subhead: Transport of Neurotransmitters

Learning Objective: Explain how neurotransmitters are transported from their site of synthesis into synaptic vesicles.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 09 - Question 57

57. What are the main structural features of the sodium–potassium ATPase?

Feedback: It is assembled from two subunits, α and β, which are responsible for the enzymatic activity of the pump, substrate binding sites and for pump function. Four transmembrane domains of the α-subunit form the transmembrane pore containing the cation-binding sites. The nucleotide binding and phosphorylation sites have been localized to the large cytoplasmic region between M4 and M5.

Subhead: Molecular Structure of Transporters

Learning Objective: Describe the molecular structure of ATPases and sodium–calcium exchangers.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 09 - Question 58

58. Why is neurotransmitter uptake physiologically relevant?

Feedback: Removing neurotransmitters from the extracellular space terminates the neurotransmitter’s actions by preventing its diffusion out of the synaptic cleft. Removing neurotransmitters from the cytoplasm provides a path for recycling neurotransmitters which can be packaged into synaptic vesicles for release.

Subhead: Significance of Transport Mechanisms

Learning Objective: Give two examples of how ion transport molecules play an active role in cell signaling.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 09 - Question 59

59. What is the mechanism of action of fluoexitine (Prozac), used in the treatment of psychiatric disorders such as depression and anxiety?

Feedback: Fluoexitine inhibits monoamine transporters. By inhibiting them, it allows monoamines to remain in the extracellular space for a longer time and act on their receptor targets.

Subhead: Significance of Transport Mechanisms

Learning Objective: Give two examples of how ion transport molecules play an active role in cell signaling.

Bloom’s Level: 3. Applying