Question 1

It is thought that the glucose transporter switches between two conformational states in a completely random fashion.How is it possible for such a system to move glucose across the membrane efficiently in a single direction?

Accepted Answer

The answer of It is thought that the glucose transporter...

Question 2

Match between columns Premises: Transporters undergo transitions between different conformations, depending on whether the substrate-binding pocket is empty or occupied.
Facilitated diffusion can be described as the favorable movement of one solute down its concentration gradient being coupled with the unfavorable movement of a second solute up its concentration gradient. The net negative charge on the cytosolic side of the membrane enhances the rate of glucose import into the cell by a uniporter. The electrochemical gradient for K⁺ across the plasma membrane is small.Therefore, any movement of K⁺ from the inside to the outside of the cell is driven solely by its concentration gradient.

Accepted Answer

The Answer of False and True is...

Question 3

Describe the two forces that drive an ion across the plasma membrane and explain how the Nernst equation takes into account both of these forces.Use the components of the equation to support your explanation and be sure to specify the assumptions being made when using the Nernst equation to calculate membrane potential.

Accepted Answer

The answer of Describe the two forces that drive an...

Question 4

Match between columns Premises: The primary mechanism by which Ca²⁺ acts as a signaling molecule is by increasing the net charge in the cytosol.
The extracellular concentration of Ca²⁺ is approximately 10⁴-fold higher than the concentration of Ca²⁺ in the cytosol.
Cytosolic Ca²⁺ concentration is kept low by the use of chelators such as EDTA.
The low cytosolic Ca²⁺ concentration sensitizes the cell to an influx of Ca²⁺, ensuring a rapid response to environmental stimuli.

Accepted Answer

The Answer of False and True is...

Question 5

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once.
$\begin{array}{lll}
\text { antiport } & \text { coupled } & \text { membrane potential } \
\text { ATP hydrolysis } & \text { electrochemical } & \text { symport } \
\text { concentration } & \text { light-driven } & \text { uniport }
\end{array}$

For an uncharged molecule, the direction of passive transport across a membrane is determined solely by its __________ gradient.On the other hand, for a charged molecule, the __________ must also be considered.The net driving force for a charged molecule across a membrane therefore has two components and is referred to as the __________ gradient.Active transport allows the movement of solutes against this gradient.The transporter proteins called __________ transporters use the movement of one solute down its gradient to provide the energy to drive the uphill transport of a second solute.When this transporter moves both ions in the same direction across the membrane, it is considered a/an __________; if the ions move in opposite directions, the transporter is considered a/an __________.

Accepted Answer

The answer of For each of the following sentences, fill...

Question 6

Identify the molecule in each pair that is more likely to diffuse through the lipid bilayer. A.amino acids or benzene B.Cl⁻ or ethanol C.glycerol or RNA D.H₂O or O₂ E.adenosine or ATP

Accepted Answer

The answer of Identify the molecule in each pair that...

Question 7

The flow of ions through a gated channel can be studied using a method called "patch-clamp recording."
A.How is a detached patch-clamp experiment set up, and what exactly does it mean to "clamp" an ion channel?
B.How is it possible to collect the recordings shown in Figures Q12-16A and Q12-16B from a single ion channel? (A)

(B)

Figure 12-16

Accepted Answer

The answer of The flow of ions through a gated...

Question 8

The toxicity of mercury depends greatly upon the formulation of the metal.Which of them (elemental, metal ion, or methyl-mercury) is more likely to be absorbed through the skin? Explain your answer.

Accepted Answer

The answer of The toxicity of mercury depends greatly upon...

Question 9

We can test the relative permeability of a phospholipid bilayer by using a synthetic membrane that does not contain any protein components.Some uncharged, polar molecules are found to diffuse freely across these membranes, to varying degrees.Which of the following has the lowest rate of diffusion across an artificial membrane? Why?

Accepted Answer

Glucose will have a negligible degree of diffusion across the synthetic bilayer.Not only is it polar, it is also larger than other molecules that are able to diffuse across the membrane.

Question 10

Order and describe all the molecular events required for the propagation of an action potential.Is propagation along the axon bidirectional? Why or why not?

Accepted Answer

The answer of Order and describe all the molecular events...

Question 11

Match between columns Premises: Gap junctions are large pores that connect the cytosol to the extracellular space. The ion selectivity of a channel depends solely on the charge of the amino acids lining the pore inside the channel.
Most ion channels are gated, which allows them to open and close in response to a specific stimulus, rather than allowing the constant, unregulated flow of ions.
Aquaporin channels are found in the plasma membrane, and allow the rapid passage of water molecules and small ions in and out of cells.

Accepted Answer

The Answer of False and True is...

Question 12

Describe the two components of an electrochemical gradient.Use your description to suggest which of the following is influenced by a larger electrochemical gradient: (1) Na⁺ moving into the cell; (2) K⁺ moving out of the cell.Explain your reasoning.

Accepted Answer

The answer of Describe the two components of an electrochemical...

Question 13

What chemical principles explain the observation that a protein-free lipid bilayer is a billion times more permeable to water than to a sodium ion?

Accepted Answer

The answer of What chemical principles explain the observation that...

Question 14

Because the Na+/K+ pump moves these ions at the same rate in opposing directions across the plasma membrane, it creates a net balance of charges on each side of the membrane .Given this fact, explain how cells generate a membrane potential across the plasma membrane and suggest the consequences for cell functions if this capacity were handicapped.

Accepted Answer

The answer of Because the Na+/K+ pump moves these ions...

Question 15

Describe the process by which gut epithelial cells use transporters to take up ingested glucose (against the concentration gradient) and to distribute glucose to other tissues by moving it back out of the cell (down the concentration gradient).

Accepted Answer

The answer of Describe the process by which gut epithelial...

Question 16

If ATP production is blocked in an animal cell, the cell will swell up.Explain this observation.

Accepted Answer

The answer of If ATP production is blocked in an...

Question 17

Match between columns Premises: Voltage-gated K⁺ channels also open immediately in response to local depolarization, reducing the magnitude of the action potential.
Voltage-gated Na⁺ channels become automatically inactivated shortly after opening, which ensures that the action potential cannot move backward along the axon.
Action potentials are usually mediated by voltage-gated Ca²⁺ channels. Neurotransmitters are small molecules released into the synaptic cleft after the fusion of synaptic vesicles with the presynaptic membrane.

Accepted Answer

The Answer of True and False is...

Question 18

The movement of glucose into the cell, against its concentration gradient, can be powered by the co-transport of Na⁺ into the cell.Explain the thermodynamic factors governing this transporter.Under what conditions would transport of glucose slow or come to a halt?

Accepted Answer

The answer of The movement of glucose into the cell,...

Question 19

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once.
$\begin{array}{lll}
\text { active } & \text { hydrophilic } & \text { noncovalent } \
\text { amino acid } & \text { hydrophobic } & \text { passive } \
\text { amphipathic } & \text { ion channels } & \text { transporter proteins }
\end{array}$

A molecule moves down its concentration gradient by __________ transport, but requires __________ transport to move up its concentration gradient.Transporter proteins and ion channels function in membrane transport by providing a __________ pathway through the membrane for specific polar solutes or inorganic ions.__________ are highly selective in the solutes they transport, binding the solute at a specific site and changing conformation so as to transport the solute across the membrane.On the other hand, __________ discriminate between solutes mainly on the basis of size and electrical charge.

Accepted Answer

The answer of For each of the following sentences, fill...

Question 20

Define homeostasis and illustrate your understanding of this concept by describing the mechanism of one transmembrane transport protein and how it contributes to homeostasis.

Accepted Answer

The answer of Define homeostasis and illustrate your understanding of...

Quiz 12: Transport Across Cell Membranes

It is thought that the glucose transporter switches between two conformational states in a completely random fashion.How is it possible for such a system to move glucose across the membrane efficiently in a single direction?

Indicate whether the statements below are TRUE or FALSE.If a statement is false, explain why it is false.

Indicate whether the statements below are TRUE or FALSE.If a statement is false, explain why it is false

Identify the molecule in each pair that is more likely to diffuse through the lipid bilayer. A.amino acids or benzene B.Cl⁻ or ethanol C.glycerol or RNA D.H₂O or O₂ E.adenosine or ATP

The toxicity of mercury depends greatly upon the formulation of the metal.Which of them (elemental, metal ion, or methyl-mercury) is more likely to be absorbed through the skin? Explain your answer.

Order and describe all the molecular events required for the propagation of an action potential.Is propagation along the axon bidirectional? Why or why not?

Indicate whether the statements below are TRUE or FALSE. If a statement is false, explain why it is false.

Describe the two components of an electrochemical gradient.Use your description to suggest which of the following is influenced by a larger electrochemical gradient: (1) Na⁺ moving into the cell; (2) K⁺ moving out of the cell.Explain your reasoning.

What chemical principles explain the observation that a protein-free lipid bilayer is a billion times more permeable to water than to a sodium ion?

Describe the process by which gut epithelial cells use transporters to take up ingested glucose (against the concentration gradient) and to distribute glucose to other tissues by moving it back out of the cell (down the concentration gradient).

If ATP production is blocked in an animal cell, the cell will swell up.Explain this observation.

Indicate whether the statements below are TRUE or FALSE.If a statement is false, explain why it is false.

The movement of glucose into the cell, against its concentration gradient, can be powered by the co-transport of Na⁺ into the cell.Explain the thermodynamic factors governing this transporter.Under what conditions would transport of glucose slow or come to a halt?

Define homeostasis and illustrate your understanding of this concept by describing the mechanism of one transmembrane transport protein and how it contributes to homeostasis.

Quiz 12: Transport Across Cell Membranes

It is thought that the glucose transporter switches between two conformational states in a completely random fashion.How is it possible for such a system to move glucose across the membrane efficiently in a single direction?

Indicate whether the statements below are TRUE or FALSE.If a statement is false, explain why it is false.

Indicate whether the statements below are TRUE or FALSE.If a statement is false, explain why it is false

Identify the molecule in each pair that is more likely to diffuse through the lipid bilayer. A.amino acids or benzene B.Cl− or ethanol C.glycerol or RNA D.H2O or O2 E.adenosine or ATP

The toxicity of mercury depends greatly upon the formulation of the metal.Which of them (elemental, metal ion, or methyl-mercury) is more likely to be absorbed through the skin? Explain your answer.

Order and describe all the molecular events required for the propagation of an action potential.Is propagation along the axon bidirectional? Why or why not?

Indicate whether the statements below are TRUE or FALSE. If a statement is false, explain why it is false.

Describe the two components of an electrochemical gradient.Use your description to suggest which of the following is influenced by a larger electrochemical gradient: (1) Na+ moving into the cell; (2) K+ moving out of the cell.Explain your reasoning.

What chemical principles explain the observation that a protein-free lipid bilayer is a billion times more permeable to water than to a sodium ion?

Describe the process by which gut epithelial cells use transporters to take up ingested glucose (against the concentration gradient) and to distribute glucose to other tissues by moving it back out of the cell (down the concentration gradient).

If ATP production is blocked in an animal cell, the cell will swell up.Explain this observation.

Indicate whether the statements below are TRUE or FALSE.If a statement is false, explain why it is false.

The movement of glucose into the cell, against its concentration gradient, can be powered by the co-transport of Na+ into the cell.Explain the thermodynamic factors governing this transporter.Under what conditions would transport of glucose slow or come to a halt?

Define homeostasis and illustrate your understanding of this concept by describing the mechanism of one transmembrane transport protein and how it contributes to homeostasis.

Identify the molecule in each pair that is more likely to diffuse through the lipid bilayer. A.amino acids or benzene B.Cl⁻ or ethanol C.glycerol or RNA D.H₂O or O₂ E.adenosine or ATP

Describe the two components of an electrochemical gradient.Use your description to suggest which of the following is influenced by a larger electrochemical gradient: (1) Na⁺ moving into the cell; (2) K⁺ moving out of the cell.Explain your reasoning.

The movement of glucose into the cell, against its concentration gradient, can be powered by the co-transport of Na⁺ into the cell.Explain the thermodynamic factors governing this transporter.Under what conditions would transport of glucose slow or come to a halt?