Block 2 Quiz Questions

Question 1

What is a GPCR?

a) glycerol phosphate-coupled receptor
b) G protein-coupled receptor
c) guanine-purine coupled receptor

Answer 1

b) G protein-coupled receptor

Question 2

In a typical GPCR, which subunit of heterotrimeric G protein is released when the receptor is activated?

a) ß - beta
b) α - alpha
c) γ - gamma

Answer 2

b) α - alpha

Question 3

If receptor activation causes a response that includes potassium channel closure, what is the cell more likely to do?

a) hyperpolarize
b) depolarize

Answer 3

b) depolarize

Question 4

Activation of certain GPCRs triggers an intracellular signaling mechanism that involves fromation of IP3 from fatty acids in the inner leaflet of the plasma membrane. IP3, a small polar molecule, is released into cytosol and stimulates a rise of cytoplasmic Ca2+ concentration. Which of the following statements best describes the Ca2+ concentration increase?

a) Ca2+ concentration increases because IP3 causes Ca2+ ions to release from the endoplasmic reticulum.
b) Ca2+ concentration increases because IP3 causes Ca2+ ions release from mitochondria.
c) Ca2+ concentration increases because IP3 causes an ATPase ion pump to shoft Ca2+ ions into the cell from the extracellular space.

Answer 4

a) Ca2+ concentration increases because IP3 causes Ca2+ ions to release from the endoplasmic reticulum.

Question 5

It is important for the cell to be able to terminate responses, and diminish responsiveness to prevent overstimulation. Cells have different mechanisms for this. One such mechanism is receptor down regulation.

a) Down regulation describes glycosylation of receptor proteins receptors on the surface of target cells in order to decrease the selectivity of ligand binding, making the cells less sensitive to a hormone or neurotransmitter.
b) Down regulation describes a decrease in a number of receptors on the surface of target cells, making the cells less sensitive to a hormone or neurotransmitter.
c) Down regulation describes a diecrease in the availability of hormones or neurotransmitters that bind to receptors on the surface of target cells, making the cells less likely to be stimulated.

Answer 5

b) Down regulation describes a decrease in a number of receptors on the surface of target cells, making the cells less sensitive to a hormone or neurotransmitter.

Question 6

Consider the internal environment in the neuromuscular junction (nerve –> muscle synapse) of a motoneuron that innervates the quadriceps of an athletic who has just run 10 kilometeres in a time of 42 minutes. Which answer best describes the intracellular ion concentrations?

a) 120mM Na+ & 5 mM K+
b) 10mM Na+ & 125 mM K+
c) 15 mM Na+ & 15 mM K+
d) 125 mM Na+ & 125 mM K+

Answer 6

b) 10mM Na+ & 125 mM K+

Question 7

PNa is a terman in the Goldman equation. If a change in PNa on a postsynaptice neuron caused a hyperpolarizing graded potential, did PNa increase of decrease?

a) PNa increased
b) PNa decreased
c) All neurotransmitter receptors are metabotropic

Answer 7

b) PNa decreased

Question 8

Which ion plays the most direct role in causing fusion of vesicles to the presynaptic membrane and subsequent release of neurotransmitter?

a) Sodium
b) Calcium
c) Hydrogen
d) Potassium

Answer 8

b) Calcium

Question 9

Proton gradients occur in mitochondria. Proton gradients also are found between the cytoplasm and the interior of lysosome, endosomes, and synaptic vesicles. Which of the following statements is NOT true?

a) The proton gradient in an endosome is created by a v-ATPase ion pump.
b) The proton gradient in a lysosome is created by a v-ATPase ion pump.
c) The proton gradient in a synaptic vesicle is created by a v-ATPase ion pump.
d) The proton gradient in a mitochondria is created by a v-ATPase ion pump.

Answer 9

d) The proton gradient in a mitochondria is created by a v-ATPase ion pump.

Question 10

In Block 1 we learned the size of a typical cell is typically measured in 10s of microns. However, some neurons in the sciatic nerve extend from the base of the spine to the foot. The sciatic nerve is the largest and longest nerve in the human body. Every person has 2 sciatic nerves, the right and left nerves—supplying each lower limb. The sciatic nerve originates in the lower spine and is formed by the combination of spinal nerves L4 to S3. Mitochondria are carried by from the cell body to the synapse via fast axonal transport. Which of the following proteins is most likely to be involved in this process?

a) Dynein
b) Vimentin
c) Kinesin

Answer 10

c) Kinesin

Question 11

In the term vATPase what does the latter “v” signify?

a) The term “v” signifies the ATPase is associated with the membrane potential (i.e. voltage).
b) The term “v” signifies the ATPase is associated with vimentin, a cytoskeletal protein.
c) The term “v” signifies the ATPase is associated with a membrane vesicle.

Answer 11

c) The term “v” signifies the ATPase is associated with a membrane vesicle.

Question 12

A graded potential can be hyperpolarizing or depolarizing. Which of these statements is TRUE?

a) A hyperpoloarizing graded potential is inhibitory to generation of an action potential.
b) A hyperpolarizing graded potential is excitatory to generation of an action potential.

Answer 12

a) A hyperpoloarizing graded potential is inhibitory to generation of an action potential.

Question 13

If a change in PNa caused a hyperpolarizing graded potential, did PNa increase or decrease?

a) PNa increased
b) PNa decreased

Answer 13

b) PNa decreased

Question 14

An mGluR receptor on a postsynaptic cell membrane has a Go G-protein. If a neurotransmitter causes receptor activation and then Go causes a sodium channel to close, what influence is this action likely to have on membrane potential in the postsynaptic cell?

a) A hyperpolarizing influence
b) A depolarizing influence

Answer 14

a) A hyperpolarizing influence

Question 15

Which ion gradient typically provides the energy for uptake of a neurotransmitter into vesicles in the presynaptic nerve terminal?

a) The potassium ion gradient.
b) The calcium ion gradient.
c) The hydrogen ion gradient.
d) The chloride ion gradient.
e) The sodium ion gradient.

Answer 15

c) The hydrogen ion gradient.

Question 16

One of the characteristics of botulinum toxin (the cause of “botulism’) is a very specific protease activity, i.e., the toxin can cleave (cut), and thereby render
“nonfunctional, a SNARE protein associated with neurotransmitter-containing synaptic vesicles found in certain nerve terminals. Which of the following is the likely effect of this toxin on fusion of synaptic vesicles with the plasma membrane (and subsequent neurotransmitter release)?

a) a decrease of fusion events
b) an increase in fusion events
c) no effect on fusion events

Answer 16

a) a decrease of fusion events

Question 17

Calculate the osmotic concentration of a solution that contains:
100 mM NaCl
12 mM NaHCO3
2 mM CaCl2
4 mM KCl
1 mM MgCl2
5 mM glucose

a) 248 mOsM
b) 124 mOsM
c) 258 mOsM
d) 243 mOsM
e) 246 mOsM

Answer 17

e) 246 mOsM

Question 18

Side 1: 10 mM KCl & 100 mM NaCl
Side 2: 100 mM KCl & 10 mM NaCl

Consider the two solutions separated by an ideal semipermeable membrane (permeable to water but impermeable to solute). Assuming complete dissociation of all the salts you can expect:

a) net water movement from side 1 to side 2
b) net water movement from side 2 to side 1
c) no net water movement

Answer 18

c) no net water movement

Question 19

Activation of certain GPCRs triggers an intracellular signaling mechanism that involves activation of adenlyl cyclase and an increase of cAMP. Which of the following statements best describes the the events that follow such a cAMP increase?

a) The cAMP increase leads to activation of protein kinase A.
b) The cAMP increase leads to activation of the release of the gamma subunit from the GPCR.
c) The cAMP increase leads to activation of protein kinase C.

Answer 19

a) The cAMP increase leads to activation of protein kinase A.

Question 20

Endothelins are 21-amino acid vasoconstricting peptides produced primarily in the endothelium. They have an important role in vascular homeostasis. Endothelin activates G protein-coupled receptors (GPCRs) ETA or ET on a target cell. Which subunit of heterotrimeitc G protein is released when the receptor is activated?

a) ß - beta
b) α - alpha
c) γ - gamma

Answer 20

b) α - alpha

Question 21

The extracellular space around axons generally has which of the following concentrations of ions (relative to intracellular concentrations)?

a) Low K, high Na, low Cl
b) High K, low Na, high Cl
c) High K, low Na, low Cl
d) Low K, high Na, high Cl

Answer 21

d) Low K, high Na, high Cl

Question 22

Opiate drugs activate metabotropic receptors. Which of the following statements on metabotropic receptors is TRUE?

a) All metabotropic receptors trigger a postsynaptic response that involves stimulation of glucose metabolism.
b) All metabotropic receptors trigger a postsynaptic response that is depolarizing.
c) Different metabotropic receptors have different effects. The postsynaptic response may be depolarizing or hypderpolarizing.
d) All metabotropic receptors trigger a postsynaptic response that is hyperpolarizing.

Answer 22

c) Different metabotropic receptors have different effects. The postsynaptic response may be depolarizing or hypderpolarizing.

Question 23

Which statement best completes the following sentence? Naloxone is sometimes used to reverse a heroin overdose because …

a) it is a receptor antagonist that attaches to opioid receptors without activating them. It binds with a higher affinity than heroin and prevents heroin’s attachment to the receptor.
b) it is a receptor antagonist that attaches to opioid receptors without activating them. It binds with a lower affinity than heroin and prevents heroin’s attachment to the receptor.

Answer 23

a) it is a receptor antagonist that attaches to opioid receptors without activating them. It binds with a higher affinity than heroin and prevents heroin’s attachment to the receptor.

Question 24

A drug like cocaine slows reuptake of the neurotransmitter dopamine from the synaptic cleft. Under normal circumstances what ion gradient provides the driving force for dopamine reuptake?

a) The proton gradient across the postsynaptic membrane.
b) The sodium gradient across the presynaptic membrane.
c) The sodium gradient across the postsynaptic membrane.
d) The proton gradient across the presynaptic membrane.

Answer 24

b) The sodium gradient across the presynaptic membrane.

Question 25

Dr. Hernandez is running a study on repetitive stimulation of a neuronal pathway. After a time, she finds evidence that suggests the sensitivity of the synapse has diminished. Which of the following is most likely to explain why this occurs? a) The number of postsynaptic receptors is increased. b) The synaptic cleft narrows. c) The number of neurotransmitter-containing vesicles in the postsynaptic cell is decreased. d) The number of postsynaptic receptors is reduced.

Answer 25

d) The number of postsynaptic receptors is reduced.

Question 26

Tight junctions form ion channels that connect neighboring epithelial cells, forming a diffusion pathway for small molecules to move from one cell to the other. Is this statement true or false? a) True b) False

Answer 26

b) False

Question 27

In 2003 Peter Agre was awarded the Nobel Prize for the discovery of aquaporins. He made the discovery almost by accident while studying blood group antigens in red cells. Which of the following best describes aquaporins? a) Aquaporins are amphipathic integral membrane proteins that form water channels. b) Aquaporins are hydrophobic integral membrane proteins that form water channels. c) Aquaporins are hydrophilic integral membrane proteins that form water channels.

Answer 27

a) Aquaporins are amphipathic integral membrane proteins that form water channels.

Question 28

Epithelia have characteristic electrical properties such as a trans epithelial electrical resistance (TEER). a) The trans epithelial electrical resistance (TEER) is an indicator of the mechanical strength of the epithelium. b) The trans epithelial electrical resistance (TEER) is an indicator of the cells' cytoskeleton to withstand mechanical stretching. c) The trans epithelial electrical resistance (TEER) is an indicator of the tightness of the epithelium.

Answer 28

c) The trans epithelial electrical resistance (TEER) is an indicator of the tightness of the epithelium.

Question 29

The columnar epithelium that lines the small intestine lumen consists of both enterocytes and goblet cells. What is your best estimate for the thickness (apical-basolateral dimension) of the enterocyte cell layer? a) 25 - 30 mM b) 0.5 - 1 µm c) 0.5 - 1 nm d) 0.5 - 1 mm e) 25 - 30 nm f) 25 - 30 µm

Answer 29

f) 25 - 30 µm

Question 30

Some epithelial cells have microvilli. In a typical epithelium, on which part of the cell are microvilli most likely to be located? a) Apical surface b) Endothelial surface c) Basolateral surface d) Basement membrane

Answer 30

a) Apical surface

Question 31

The selective permeability of tight junctions (TJs) is primarily influenced by a) which connexin proteins are associated with the TJ complex b) which claudin proteins are associated with the TJ complex c) which desmosome proteins are associated with the TJ complex d) which synaptotagmin proteins are associated with the TJ complex

Answer 31

b) which claudin proteins are associated with the TJ complex

Question 32

Cell polarity is a specific term. When applied to epithelial cells, what best describes the meaning of cell polarity? a) Cell polarity refers to cells that have either a positive or negative resting membrane potential. b) Cell polarity refers to the intrinsic asymmetry of cells that have distinct apical and basolateral region. c) Cell polarity refers to cells that have a negative resting membrane potential. d) Cell polarity refers to the intrinsic symmetry of cells that have two identical apical regions on both sides of the cell.

Answer 32

b) Cell polarity refers to the intrinsic asymmetry of cells that have distinct apical and basolateral region.

Question 33

Cells like pancreatic acinar cells form and release secretory vesicles. SNARE proteins play a functional role. Which of the following statements best describes the proteins called v-SNARES. a) v-SNARES are proteins contained inside of secretory vesicles that help stabilize the vesicle contents until the vesicle fuses with the cytosolic face of the plasma membrane. b) t-SNARES are proteins on the surface of vesicles that help the vesicle fuse with v-SNARES on the sytosolic face of the plasma membrane. c) v-SNARES are proteins on the surface of vesicles that help the vesicle fuse with t-SNARES on the cytosolic face of the plasma membrane.

Answer 33

c) v-SNARES are proteins on the surface of vesicles that help the vesicle fuse with t-SNARES on the cytosolic face of the plasma membrane.

Question 34

Epithelial cells (enterocytes) that line the intestinal tract have a specialized apical surface called a brush border: an array of membrane protrusions known as microvilli. a) The structure of the microvilli is defined mainly by tubulin microfilaments. b) The structure of a microvilli is defined mainly by action microtubules. c) The structure of the microvilli is defined mainly by action microfilaments. d) The structure of the microvilli is defined mainly by ZO1 proteins. e) The structure of the microvilli is defined mainly by centrosome microfilaments.

Answer 34

c) The structure of the microvilli is defined mainly by action microfilaments.

Question 35

Epithelial cell polarity is influenced by a cell's attachments to the extracellular matrix. Which of the following statements best describes such attachments? a) The basolateral surface typically interacts with the extracellular matrix. b) The apical surface typically interacts with the extracellular matrix.

Answer 35

a) The basolateral surface typically interacts with the extracellular matrix.

Question 36

A semipermeable membrane separates two solutions, Side A containing 0.5 mM glucose and Side B 1 mM glucose. In which direction would you predict diffusion of glucose to occur? a) Unidirectional flux from A to B b) Net flux from B to A c) Net flux from A to B d) Unidirectional flux from A to B

Answer 36

b) Net flux from B to A

Question 37

What best completes the following statement? The rate of diffusion of a solute across a membrane … a) is dependent on both permeability and the concentration gradient. b) is dependent on the concentration gradient but independent of permeability. c) is dependent on permeability but independent of the concentration gradient. d) does not depend on either permeability or the concentration gradient.

Answer 37

a) is dependent on both permeability and the concentration gradient.

Question 38

What best completes the following statement? In determining the cell membrane permeability of a solute … a) molecular size of the solute is less important than partition coefficient. b) molecular size of the solute is more important than partition coefficient. c) neither molecular size of the solute not its partition coefficient is important.

Answer 38

a) molecular size of the solute is less important than partition coefficient.

Question 39

Calculate the theoretical osmotic concentration of a solution that contains: 110 mM NaCl 5 mM KCl 25 mM NaHCO3 3 mM CaCl2 a) 286 mOsM b) 314 mOsM c) 143 mOsM d) 289 mOsM

Answer 39

d) 289 mOsM

Question 40

Is the following statement true or false? Uncharged (nonionized) molecules generally have a greater permeability across the plasma membrane than ionized molecules. a) True b) False

Answer 40

a) True

Question 41

Inhibition of the Na,K-ATPase might reasonably result in which of the following: a) reduced activity of many secondary active transporters b) gradual decrease in cytoplasmic Na+ c) hyperpolarization of the membrane potential d) gradual cellular accumulation of K+ e) cell shrinkage

Answer 41

a) reduced activity of many secondary active transporters

Question 42

If the postsynaptic cell's plasma membrane were to become substantially more permeable to Na+, you would expect the membrane potential to [depolarize, hyperpolarize] __________________. You would expect the membrane potential to depolarize if the extracellular K+ concentration were to [increase, decrease] ______________. a) depolarize, decrease b) hyperpolarize, increase c) hyperpolarize, decrease d) depolarize, increase

Answer 42

d) depolarize, increase

Question 43

It is important for the cell to be able to terminate responses, and diminish responsiveness to prevent overstimulation. Cells have different mechanisms for this. One such mechanism is receptor down regulation. a) Down regulation describes glycosylation of receptor proteins receptors on the surface of target cells in order to decrease the selectivity of ligand binding, making the cells less sensitive to a hormone or neurotransmitter. b) Down regulation describes a decrease in the availability of hormones or neurotransmitters that bind to receptors on the surface of target cells, making the cells less likely to be stimulated. c) Down regulation describes a decrease in the number of receptors on the surface of target cells, making the cells less sensitive to a hormone or neurotransmitter.

Answer 43

c) Down regulation describes a decrease in the number of receptors on the surface of target cells, making the cells less sensitive to a hormone or neurotransmitter.

Question 44

Jose measures membrane potential in two neighboring cells. He notices that when the membrane potential changes in one cell, the membrane potential of the neighboring cell changes in a similar manner. For example, if one cell hyperpolarizes, the neighboring cell also hyperpolarizes. He concludes the cells are electrically coupled. Which of the following is the most likely to cause the electrical coupling? a) The electrical coupling is most probably due to tight junctions that connect the two cells. b) The electrical coupling is most probably due to gap junctions that connect the two cells. c) The electrical coupling is most probably due to desmosomes that connect the two cells. d) The electrical coupling is most probably due to integrins that connect the two cells.

Answer 44

b) The electrical coupling is most probably due to gap junctions that connect the two cells.

Question 45

Typically, there is an ion gradient between the cytoplasm and the interior of synaptic vesicles. The ion gradient has a functional role. Which of the following statements best describes the ion gradient across the synaptic vesicle membrane and its role? a) There is a sodium gradient across the synaptic vesicle membrane, and it provides the driving force for the transport of neurotransmitter out of the vesicle. b) There is a proton gradient across the synaptic vesicle membrane, and it provides the driving force for the transport of neurotransmitter into the vesicle. c) There is a sodium gradient across the synaptic vesicle membrane, and it provides the driving force for the transport of neurotransmitter into the vesicle. d) There is a proton gradient across the synaptic vesicle membrane, and it provides the driving force for the transport of neurotransmitter out of the vesicle.

Answer 45

b) There is a proton gradient across the synaptic vesicle membrane, and it provides the driving force for the transport of neurotransmitter into the vesicle.

Question 46

System 1 Side A - 3 mM Side B - 5 mM System 2 Side A - 0 mM Side B - 1 mM Consider the two systems shown in the figure. In each system, two solutions containing the indicated concentrations of a solute ("compound X") are separated from one another by a membrane freely permeable to X. To keep it simple, X is not charged, and let's not worry about any movement of water. Based on the information given, which of the following statement is true. (more than one may be correct) a) In each system, the net flux of X is from side B to side A. b) Neither of these issues can be reasonabily predicted from the information given. c) In each system, the net flux of X is from side A to side B.

Answer 46

a) In each system, the net flux of X is from side B to side A.

Question 47

Many polar metabolites and nutrients are trans;orted across the plasma membrane by carriers. Which of the following are NOT characteristics of carriers? a) carriers show saturability b) carriers show substrate selectivity c) carriers cannot be inhibited

Answer 47

c) carriers cannot be inhibited

Question 48

Is the following statement true or false? When a substrate binds to a carrier, the carrier forms a hydrophobic pore that crosses the lipid bilayer. a) True b) False

Answer 48

b) False

Question 49

Jmax is a term that is often used to characterize a carrier. Which of the following statement best describes Jmax? a) Max is the concentration required to increase the rate of transport by 50% b) Jmax is the maximum number of substrate molecules that can bind to the carrier c) Jmax is the maximum rate of transport d) Jmax is the maximum number of different substrates that can bind to the carrier

Answer 49

c) Jmax is the maximum rate of transport

Question 50

Dr Renko observes that an inhibitor molecule Acme771 attaches to the same binding site used by the substrate for the carrier. What is the most likely type of inhibition cause by Acme771? a) Noncompetitive b) Competitive c) Neither noncompetitive nor competitive

Answer 50

b) Competitive

Question 51

Is the following statement true or false? Primary active transporters always move solute across the plasma membrane. a) True b) False

Answer 51

b) False

Question 52

The difference between active transport (AT) and facilitated diffusions (FD) is: a) FD can move substrate against an electrochemical gradient, AT cannot b) AT is both saturable and selective, FD is not c) AT only supports transport of inorganic ions, FD only supports transport of organic compounds d) AT can move substrate again an electrochemical gradient, FD cannot e) FD is both saturable and selective, AT is not

Answer 52

d) AT can move substrate again an electrochemical gradient, FD cannot

Question 53

Which of the following distinguishes Primary Active Transport (AT) from Secondary Active Transport (AT)? a) Secondary AT can move a substrate against an electrochmical gradient, primary AT cannot b) Secondary AT makes direct use of ATP, primary AT does not c) Primary AT can move a substrate against an electrochemical gradient, secondary AT cannot d) Primary AT makes direct use of ATP, secondary AT does not e) Secondary AT is saturable and selective, primary AT is not f) Primary AT is saturable and selective, secondary AT is not

Answer 53

d) Primary AT makes direct use of ATP, secondary AT does not

Question 54

If the Na, K-ATPase is inhibited (e.g., by ouabain), you can expect: a) Intracellular Na+ and K+ to increase b) Intracellular Na+ and K+ to decrease c) Intracellular Na+ to increase and intracellular K+ to decrease d) Intracellular Na+ to decrease and intracellular K+ to increase

Answer 54

c) Intracellular Na+ to increase and intracellular K+ to decrease

Question 55

Rapid, continuous activation of skeletal muscle can result in a gradual increase in cytoplasmic Na+ concentration (for reasons that we will discuss in upcoming lectures). One regulatory response is the phosphorylation of the γ-regulatory sub unit of the Na,K-ATPase (i.e., 'phospholemman') which then exerts a regulatory effect on Na,K-ATPase activity to bring intracellular Na+ back down toward its normal level. Which of the following responses of the Na,K-ATPase to the phosphorylation of phospholemman would, in principal, have this effect? a) Increase in the K0.5 for Na+ efflux b) Decrease in the K0.5 for Na+ efflux c) Increase in the K0.5 for Na+ uptake d) Decrease in the K0.5 for Na+ uptake

Answer 55

b) Decrease in the K0.5 for Na+ efflux

Question 56

SERT is a transporter that neurons use to shift serotonin from the synaptic cleft into the presynaptic meuron. Which of the following statements is most likely to describe the transporter's source of energy? a) SERT hydrolyzes ATP. b) SERT uses the energy of the Na+ gradient across the membrane c) SERT uses the energy of the H+ gradient across the membrane.

Answer 56

b) SERT uses the energy of the Na+ gradient across the membrane

Question 57

The inside negative membrane potential is a force that helps support a) the movement of cations into the cell b) the movement of (neutral) nonelectrolytes out of the cell c) the movement of (neutral) nonelectrolytes into the cell d) the movement of anions into the cell

Answer 57

a) the movement of cations into the cell

Question 58

Some cells in the pancreatic acinus form vesicles containing zymogens. Then the cells secrete the zymogens. Certain proteins called v-SNARES play a role in this process. What best describes the proteins called v-SNARES? a) v-SNARES are proteins on the cytosolic face of the plasma membrane that help vesicles to fuse with the plasma membrane. b) v-SNARES are proteins on the surface of vesicles that help the vesicle fuse with the cytosolic face of the plasma membrane. c) v-SNARES are proteins contained inside of vesicles that help stabilize the vesicle contents until the vesicle fuses with the cytosolic face of the plasma membrane. d) v-SNARES are a type of glycophingolipid in the vesicle lipid bilayer that help maintain vesicle integrity.

Answer 58

b) v-SNARES are proteins on the surface of vesicles that help the vesicle fuse with the cytosolic face of the plasma membrane.

Question 59

The basolateral surface of the airway epithelium interacts with the extracellular matrix (ECM) and adjacent cells. Integrins stabilize the cell by attaching the cell's cytoskeleton to the ECM. The integrin protein, which passes through the plasma membrane, interacts with the extracellular matrix outside the cell, and the cytoskeleton inside the cell. What best describes how integrins are formed? a) Integrins are translated by ribosomes located in the cytoplasm beneath the apical surface of the cell. b) Integrins are translated by ribosomes located in the cytoplasm beneath the basolateral surface of the cell. c) Integrins are translated by ribosomes attached to the rough endoplasmic reticulum, with their ECM binding site facing the lumen. d) Integrins are translated by ribosomes attached to the rough endoplasmic reticulum, with the ECM binding site facing away from the lumen.

Answer 59

c) Integrins are translated by ribosomes attached to the rough endoplasmic reticulum, with their ECM binding site facing the lumen.

Question 60

The trans epithelial electrical resistance (TEER) is a characteristic property of an epithelium. Which of the following statements best describes the TEER? a) A high trans epithelial electrical resistance (TEER) is an indicator of a tight epithelium in which paracellular diffusion of solute is likely to be low. b) A high trans epithelial electrical resistance (TEER) is an indicator of a leaky epithelium in which paracellular diffusion of a solute is likely to be high. c) A high trans epithelial electrical resistance (TEER) is an indicator of a tight attachment between the epithelium and the basement membrane in which diffusion of solute across the basolateral surface is likely to be low.

Answer 60

a) A high trans epithelial electrical resistance (TEER) is an indicator of a tight epithelium in which paracellular diffusion of solute is likely to be low.

Question 61

Dr Renko studied diffusion of tracer molecules to study paracellular diffusion across an epithelial monolayer of Caco-2 cells. The tracers were fluorescently labelled dextran molecules of different molecular weight. She is screening various drugs to determine whether they affect the cells in any way. Which drugs are most likely to change paracellular diffusion? a) Drugs that modify tight junctions are the most likely to change paracellular diffusion. b) Drugs that modify with aquaporins are the most likely to change paracellular diffusion. c) Drugs that modify microvilli are the most likely to change paracellular diffusion. d) Drugs that modify gap junctions are the most likely to change paracellular diffusion.

Answer 61

a) Drugs that modify tight junctions are the most likely to change paracellular diffusion.

Question 62

Ion channel behavior is sometimes called "stochastic." Which of the following best describes the meaning of this term? a) Stochastic behavior indicates a degree of predictability. b) Stochastic behavior indicates a degree of randomness and uncertainty. c) Stochastic behavior indicates adherence to a linear pattern. d) Stochastic behavior indicates adherence to defined rhythm.

Answer 62

b) Stochastic behavior indicates a degree of randomness and uncertainty.

Question 63

Dr. Renko occasionally uses a patch clamp technique to study ion channels. Which of the following best describes this methodology? a) The patch clamp technique measures the small changes in ion concentration that occur when ions flow through channels. b) The patch clamp technique measures the small changes in lipid fluidity that occur when a patch pipette makes contact with the membrane in the vicinity of ion channels. c) The patch clamp technique measures electrical current that occurs when ions flow through channels. d) The patch clamp technique measures the small changes in tensile strength of the membrane that occurs when ions flow through channels.

Answer 63

c) The patch clamp technique measures electrical current that occurs when ions flow through channels.

Question 64

What best completes the following statement? When calcium ion channels in the plasma membrane are in the open state, the rate of passage of calcium ions across the membrane... a) ...is dependent on both membrane potential and the concentration gradient. b) ...is dependent on the concentration gradient but independent of membrane potential. c) ...is dependent on membrane potential permeability but independent of the concentration gradient.

Answer 64

a) ...is dependent on both membrane potential and the concentration gradient.

Question 65

Imagine a neuron that receives a stimulus that causes a graded depolarization. What is the response most likely caused by? a) An increase in the open probability of sodium channels. b) An increase in the open probability of potassium channels.

Answer 65

a) An increase in the open probability of sodium channels.

Question 66

Dr. Renko's research laboratory is studying high-conductance potassium channels. Because they allow movement of charged particles (potassium ions), the channels have certain electrical properties. In the context of ion channel characteristics, which of the following best describes the meaning of the term "electrical conductance"? a) The electrical conductance of a channel is a measure of the threshold voltage for channel opening. b) The electrical conductance of a channel is a measure of the channel's electrical resistance. c) The electrical conductance of a channel is the inverse of the channel's electrical resistance. d) The electrical conductance of a channel is a measure of the threshold voltage for channel closing.

Answer 66

c) The electrical conductance of a channel is the inverse of the channel's electrical resistance.

Question 67

What percentage of children born ot a couple in which (i) the father carries on mutant CFTR gene and (ii) the mother carries no mutant CFTR genes can be expected to develop cystic fibrosis? a) 50% b) 25% c) 100% d) 0%

Answer 67

d) 0%

Question 68

The major stimulus of pancreatic zymogen secretion is: a) acetylcholine (ACh) released from vagal nerves b) cephalic parasympathetic activity c) secretin released from duodenal S-cells d) gastrin released from stomach cells e) cholecystokinin (CCK) released from duodenal I-cells

Answer 68

e) cholecystokinin (CCK) released from duodenal I-cells

Question 69

The major stimulus of pancreatic secretion of NaHCO3 and water is: a) acetylcholine (ACh) released from vagal nerves b) cephalic parasympathetic activity c) secretin released from duodenal S-cells d) gastrin released from stomach cells e) cholecystokinin (CCK) released from duodenal I-cells

Answer 69

c) secretin rleased from duodenal S-cells

Question 70

Failure of CFTR in pancreatic duct cells results in: a) Increased recycling of Cl- across the luminal membrane, leading to a futile cycle of energy waste b) the runaway alkalinization of the ductal lumen and a subsequent increase in zymogen delivery to the intestine c) increased water secretion across the ductal epithelium, leading to increased zymogen delivery to the intestine d) decreased recycling of Cl- across the luminal membrane, leading to the net loss of luminal Cl- and the subsequent inhibition of apical Cl/HCO3 exchange

Answer 70

d) decreased recycling of Cl- across the luminal membrane, leading to the net loss of luminal Cl- and the subsequent inhibition of apical Cl/HCO3 exchange

Question 71

The predominant chloride channel in pancreatic acinar cells is ________ (CFTR; CLCA), whereas the predominant chloride channel in pancreatic duct cells is ________ (CFTR; CLCA). a) CFTR, CLCA b) CFTR, CFTR c) CLCA, CLCA d) CLCA, CFTR

Answer 71

d) CLCA, CFTR

Question 72

Dr. Renko's research laboratory is studying potassium channels in AC981 cells. She tests a new drug K-Pop that she predicts will increase the open probability of the channels. Which of the following statements best describes the outcome? a) If K-POP increases the open probability of the potassium channels the cell resting potential will shift in a depolarizing direction. b) If K-POP increases the open probability of the potassium channels the cell resting potential will shift in a hyperpolarizing direction. c) If K-POP increases the open probability of the potassium channels the cell resting potential will not change.

Answer 72

b) If K-POP increases the open probability of the potassium channels the cell resting potential will shift in a hyperpolarizing direction.

Question 73

Dr. Renko asks her junior colleague Irina to measure ion concentrations in A981 cells to determine the effect of eliminating K+ ions from the extracellular medium. The cells were placed in K+-free medium for 90 min. Which of the following is most likely to be the result? (Hint: Keep in mind the way Na,K-ATPase works) a) Irine observes a decrease of intracellular Na+ in cells that were exposed to K+ free medium. b) Irina observes a decrease of intracellular K+ in cells that were exposed to K+ free medium. c) Irina observes an increase of intracellular K+ in cells that were exposed to K+ free medium.

Answer 73

b) Irina observes a decrease of intracellular K+ in cells that were exposed to K+ free medium.

Question 74

The Michaelis Menten relationship of a particular glucose transporter can be written in the form of an equation. In the version of the shown below, one part of the equation is missing and has been replaced with "?" J = Jmax [glucose] Kt + ? Which of the following is the correct term that replaces the "?" a) Jmax b) 1/Kt c) V d) [glucose]

Answer 74

d) [glucose]

Question 75

Eadie-Hofstee plots can be used to analyze the characteristics of a solute carrier and the responses of the carrier to an inhibitor. Which of the Eadie-Hofstee plots presented below best describes the expected kinetic profile of non-competitive inhibition? (In each graph Control = black line; Inhibitor-treated = red line)

Answer 75

Negative slope control line parallel to and above the inhibitor-treated line

Question 76

Dietary glucose uptake involves Na+-glucose cotransport by cells that line the small intestine. If you eat a meal high in carbohydrate content, which of the following is most likely to happen? a) Na, K-ATPase activity of small intestine cells is likely to decrease. b) Na, K-ATPase activity of small intestine cells is likely to increase. c) Na, K-ATPase activity of small intestine cells is likely to remain unchanged.

Answer 76

b) Na, K-ATPase activity of small intestine cells is likely to increase.