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CELL BIOLOGY CHAPTER 11
Terms in this set (46)
The permeability of a protein-free lipid bilayer to various molecules depends on their properties. Sort the following in order low to high permeability from left to right.
1. RNA oligonucleotide 2. ATP 3. Na+ 4. Glucose 5. Urea
Why do cells not have membrane transport proteins for O2?
Because oxygen can dissolve in the lipid bilayer and diffuse in and out rapidly without the need for a transporter
For which of the following ions is the intracellular concentration typically higher than the extra cellar concentration?
Imagine a small synthetic vesicle made from pure phospholipids enclosing an interior lumen containing 1 mM glucose and 1 mM sodium chloride. If the vesicle is placed in pure water, which of the following happens faster?
H2O diffused in
In contrast to transporters, the channel proteins in cellular membranes...
Can only mediate passive transport
Based on the graph, which of the following describes the effect of cocaine on the kinetics of dopamine reuptake by the transporter?
In the presence of cocaine, the material rate of transport (Vmax) is unaffected, but the apparent affinity of the transporter for dopamine is reduced
Which of the following transporters mediates primary active transport when transporting the solutes in the directions indicated? The concentration of both solutes (shown as small circles and squares) is higher outside of the cell?
Small circle and the square are going outside
The lactose permease in E. coli is an H+ - lactose symporter that mediates the inward active transport of lactose if this sugar is present in the environment instead of glucose. Which of the following is true about this transporter?
Is has a twofold pseudosymmetrical structure
Which if the following normally functions to lower the pH of the cytosol?
A Na+ -Independent CI^-, HCO3^- exchanger in the plasma membrane
Many amino acids in our diet are absorbed via the transcellular transport pathway by the intestinal epithelial cells. This process requires ATP hydrolysis by...
The Na+ -K+ pumps in the basal and lateral domains of the plasma membrane
The family of ATPases is structurally related to the turbine-like pumps that acidify lysosomes and vesicles; however, they usually function in reverse, generating ATP from ADP and Pi using proton gradients across membranes. What are they called?
Indicate whether each of the following descriptions matches an ABC transporter (A), a P-type pump (P), or a V-type pump (V). Your answer would be a five-letter string composed of letters A, P, and V only
P. The pumps in the family are phosphorylated at a key Asp residue in each transport cycle
A. This family is the largest among membrane transport proteins and includes some channels as well as pumps
V. The pumps in this family are responsible for the acidification of synaptic vesicles
P. The sodium-potassium pump is a member of this family
A. The multi drug resistance protein is a member of this family
Which of the following transporters is NOT electrogenic?
Na+- independent CI-HCO3- exchanger
Most eukaryotic ABC transporters are involved in exporting small molecules from the cytosol. In this subset of the ABC transporters, does the small molecule bind better to the ATP-bound (B) or the ATP-free (F) transporter?
Which of the following is a pump that hydrolyzes two ATP molecules per transport cycle?
The multi drug resistance protein
An ion channel...
All the above
1. Always mediates passive transport
2. Is ion-selective
3. Is typically several orders of magnitude faster than a transporter
4. Is usually gated
The Nernst equilibrium potential for an ion that is 10 times more concentred in the cytosol compared to the extracellular fluid is about -60 mV. How much would the potential be if the extracellular concentration decreases 100-fold with no changes in the intracellular concentration?
The membrane potential in a particular hyper polarized cell is measured to be -70 mV. For each of the following channels in this cell, the calculated Nernst equilibrium potential for the corresponding ion is passed. Indicate whether each channel is driven to pass the ion into (I) or out (O) of the cell. Your answer would be a four-letter string composed of letter I and O only
Sanshool is a natural compound found in Sichuan pepper, which is commonly used in making spicy Asian food, and creates a numbing sensation in the mouth. It is known to inhibit a subset....How do you think sanshool affects these sensory neurons?
It elevates the resting potential (to less negative values) and makes it easier to excite the neurons
Which of the following is correct regarding the electrical properties of cellular membranes?
none of the above
A membrane potenial is plotted over time in the following graph. The Nernst equilibrium potentials for four ions (A to D) that affect the membrane potential in this system are indicated in the graph. What happened in the time period indicated by a question mark?
Channels conducting ion D opened
A potassium channel conducts K+ ions several orders of magnitude better than Na+ ions, because...
The Na+ ions is too small to interact with the channel in a way that facilitates the loss of water from the ion
Which of the following is the reason why an aquaporin does not pass ions through?
The Na+ ions do not favorably interact with the wall of the pore and therefore cannot be dehydrated
Aquaporin has a pair of key asparagine residues located on the wall almost halfway though its pore. These residues simultaneously bind to the oxygen atom of a passing water molecule, rendering it unavailable
The channel cannot conduct protons
MscS and MscL are mechanosensitive channels that...
Open in response to membrane tension
A neuron's repetitive firing rate is limited by an absolute refractory period, during which a new action potential cannot be generated. Which event is chiefly responsible for this limit?
Inactivation of voltage-gated Na+ channels
If the extracellular concentration of sodium ions is artificially decreased for a neuron...
The resting potential hardly changes but the action potential peak is lowered
Which of the following situations in a neuron results in action potentials that have extended depolarization phases?
Compromising the inactivation mechanism in voltage-gated Na+ channels
Myelination of axons in the peripheral nervous system...
All of the above
Once expressed in a neuron in the mouse brain and subjected to a flash of light, how does channel rhodopsin affect the membrane potential?
It depolarizes the membrane, leading to the opening of voltage-gate Na+ channels
In a voltage-clamp experiment on a squid giant axon, the membrane potential is clamped at +20 mV, as shown below. Within the same time frame, which of the curves A to D better show qualitatively how the total membrane current changes? A positive value of the current represents an outward flow of cations.
C - bigger dotted line
Voltage-gated cation channels in the plasma membrane of a neuron open when the membrane potential passes a threshold value that is about 20 mV above the resting potential.
18 pN, toward the cell exterior
Which of the following graphs better represents the change in the relative conductance of Na+ and K+ channels during an action of potential in a neuronal membrane?
B - K+ is before Na+
Indicated true (T) and false (F) statements below regarding ion channels in cellular membranes. Your answer would be a four-letterr string go composed of letter
(T) With patch-clamp recordings, it is possible to study ion transport through single molecule of a channel protein.
(F) Cells that are not electrically excitable often lack gated ion channels in their plasma membrane
(F) The aggregate current crossing a patch of plasma membrane represents the degree to which each individual channel is open at that time
(F) Patch-clamp recordings have shown that any voltage-gated ion channel opens as soon as the membrane potential is altered
In neurons, the synapotagmin-1 protein is localized to presynaptic axon terminal. When activated, t facilitates the fusion of neurotransmitter-containing synaptic vesicles to the plasma membrane, leading to neurotransmitter release into the synaptic cleft. Which of the following would you expect to directly activate synaptotagmin-1 for this function?
Binding to Ca2+
A certain neuron is a mouse brain is firing about 300 times per second, whereas almost all of its neighboring neurons are firing at much lower rates of only a few times per second. This implies that...
It is probably of a different type compared to most of its neighbors
From left to right, indicate whether the transmitter-gated channels for (1) calcium, (2) chloride, (3) potassium, and (4) sodium at a chemical synapse usually open in response to excitatory (E) or inhibitory (I) neurotransmitter. Your answer would be a four-letter
Astrogial cells in the brain can actively import the amino acids glutamate from the synaptic cleft, convert it to the amino acid glutamine, and release the glutamine into the cleft to glutamate Why is this function of glial cells important?
Because glutamate is an excitatory neurotransmitter and should be cleared from the synaptic cleft rapidly after its release
The nicotinic acetylcholrine receptor is an ionotropic receptor that an be activated by nicotine,
Neuromuscular transmission involves the sequential activation of several ion channels.
(E) Opening of voltage-gated Ca2+ channels in the motor neuron
(C) Opening of inotropic acetylcholine receptors on the muscle cell plasm membrane
(A) Opening of voltage-gated Na+ channels in the muscle cell plasma membrane
(D) Opening of voltage-gated Ca2+ channels in the T tubules
(B) Opening of Ca2+ release channels in the sarcoplamic reticulum membrane
Dopamine is a neurotransmitter involved in the reward pathways in the brain, and it's decreased activity has been associated with diseases such as Parkinson's disease and attention deficit/hyperactivity. Which of the following drugs is NOT a likely candidate to treat these diseases?
Chlorpromazine, a dopamine antagonist that binds to an inhibits dopamine receptors
Each single neuron acts as a computational device. Typically, the magnitude of the combined postsynaptic potential is encoded in the...of firing of action potentials in the postsynaptic neuron
Which of the following better represents the process of adaptation mediated by the voltage-gated Ca2+ channels and Ca2+ - activated K+ channels? The vertical axis, while he horizontal axis is the time of constant stimulation (in milliseconds)
D) Three peaks. Two similar and one wide
The inactivation rate of voltage-gated Na+ and K+ channels can regulate the firing frequency of neurons. Which of the following combinations results in the highest firing frequency?
Rapid inactivation of both Na+ and K+ channels
Which of the following is NOT common between long-term potentiation and long-term depression?
They both result result in an enhanced postsynaptic response
Sorry the following events in a sequence that would lead to long-term potentiation (LTP).
(B) Glutamate release into the synaptic clefts
(A) Activation of AMPA receptors
(D) Postsynaptic membrane depolarization
(E) Activation of NMDA receptors
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