Question 1

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following ions is the most abundant inside a typical mammalian cell?

Accepted Answer

Potassium (K+) is the most abundant ion inside a typical mammalian cell, with a concentration that is usually 10-30 times higher inside the cell than outside. Sodium (Na+) is also present, but at lower concentrations than potassium. Calcium ions (Ca2+) are stored in organelles like the endoplasmic reticulum and mitochondria, and only small amounts are free in the cytoplasm. Chloride ions (Cl-) are abundant outside the cell but are kept at low concentrations inside the cell.

Question 2

Ion channels are classified as membrane transport proteins.They discriminate between ions based on size and charge.In addition to Na⁺, which one of the following ions would you expect to be able to freely diffuse through a Na⁺ channel? Explain your answer.

Accepted Answer

H⁺ ions are small and positively charged, similar to Na⁺, which allows them to pass through Na⁺ channels more easily compared to other ions with different charges or larger sizes.

Question 3

Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found?

Accepted Answer

Aquaporins facilitate the movement of water across cell membranes and do not directly generate a change in voltage, as they do not transport charged particles (ions). Sodium, calcium, and proton channels, on the other hand, are involved in the movement of ions across membranes, which can generate changes in voltage.

Question 4

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient.This type of transport is called

Accepted Answer

Pumps are able to move solutes against their concentration gradient, which requires the expenditure of cellular energy. This type of transport is called active transport. Free diffusion, facilitated diffusion, and passive transport do not require energy input from the cell.

Question 5

Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients.Which of the following is NOT one of the common ways to perform active transport?

Accepted Answer

The correct options for common ways to perform active transport include Na+/K+-coupled (not solely K+), ATP-driven, and light-driven mechanisms. The option listed as "K⁺-coupled" does not represent a standard or recognized form of active transport mechanism, making it the incorrect choice.

Question 6

Which of the following statements about resting membrane potential is FALSE?

Accepted Answer

The answer of Which of the following statements about resting...

Question 7

Transporters, in contrast to channels, work by

Accepted Answer

Transporters work by recognizing and binding specific substrates and then undergoing a conformational change to transport them across the membrane. Channels, on the other hand, allow passive movement of solutes down their concentration gradient without specific recognition. Filtering by charge and size are not mechanisms used by either transporters or channels.

Question 8

Negatively charged ions are required to balance the net positive charge from metal ions such as K⁺, Na⁺, and Ca²⁺.Which of the following negatively charged ions is the most abundant outside the cell and which ion most often neutralize (written in parentheses)?

Accepted Answer

The most abundant negatively charged ion outside the cell is Cl-, and it most often neutralizes the net positive charge from Na+ ions, which is the case for the metal ions listed in option D (Na⁺). Thus, option D is the best choice.

Question 9

Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules.In the extracellular case, what is the principal anion?

Accepted Answer

The principal anion in the extracellular environment is chloride (Cl-).

Question 10

Which of the following statements is TRUE?

Accepted Answer

The answer of Which of the following statements is TRUE?
...

Question 11

You have generated antibodies that recognize the extracellular domain of the Ca²⁺-pump.Adding these antibodies to animal cells blocks the active transport of Ca²⁺ from the cytosol into the extracellular environment.What do you expect to observe with respect to intracellular Ca²⁺?

Accepted Answer

The answer of You have generated antibodies that recognize the...

Question 12

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following negatively charged ions is NOT primarily used to buffer positive charges inside the cell?

Accepted Answer

Cl^- (chloride ion) is not primarily used to buffer positive charges inside the cell. Instead, it is more involved in maintaining osmotic balance and electrical neutrality by balancing out positive ions outside the cell.

Question 13

Cells make use of H⁺ electrochemical gradients in many ways.Which of the following proton transporters is used to regulate pH in animal cells?

Accepted Answer

The Na+/H+ exchanger is used to regulate pH in animal cells by exchanging sodium ions (Na+) for protons (H+), effectively removing excess H+ from the cell to maintain pH balance.

Question 14

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following ions is the most abundant outside a typical mammalian cell?

Accepted Answer

Sodium ions (Na+) are the most abundant ions outside of a typical mammalian cell, playing a crucial role in maintaining the cell's electrochemical gradient.

Question 15

Below is a list of molecules with different chemical characteristics.Knowing that all molecules will eventually diffuse across a phospholipid bilayer, select the option below that most accurately predicts the relative rates of diffusion of these molecules (fastest to slowest).
Alanine estrogen propanol sodium

Accepted Answer

Estrogen, being a steroid hormone, is lipid-soluble and diffuses through the lipid bilayer most rapidly. Propanol, a small, somewhat polar molecule, diffuses more slowly. Alanine, a small amino acid with both polar and ionic properties, diffuses even more slowly. Sodium ions, being charged, have the slowest diffusion rate through the nonpolar lipid bilayer without assistance.

Question 16

Which of the following occur WITHOUT coupling transport of the solute to the movement of a second solute?

Accepted Answer

Export of Ca²⁺ from the cytosol occurs through a calcium pump that does not couple transport to the movement of a second solute. The other options involve the coupling of solute transport to the movement of a second solute.

Question 17

A hungry yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process: C₆H₁₂O₆ + 2ADP + 2P_i + H⁺ → 2CO₂ + 2CH₃CH₂OH + 2ATP + 2H₂O Unfortunately, the grape juice is contaminated with proteases that attack some of the transport proteins in the yeast cell membrane, and the yeast cell dies.Which of the following is the most likely cause of the yeast cell's demise?

Accepted Answer

Without transport proteins, the yeast cell cannot import sugar from the grape juice, and thus cannot produce the energy (ATP) needed to survive. The toxic buildup of carbon dioxide and ethanol may contribute to the yeast cell's demise, but the inability to import sugar is the primary cause of its death. Diffusion of ATP out of the cell is not a likely cause of death, as ATP is produced inside the cell and used for energy within the cell.

Question 18

The Na⁺-K⁺ ATPase is also known as the Na⁺-K⁺ pump.It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration.What happens immediately after the pump hydrolyzes ATP?

Accepted Answer

The immediate effect of ATP hydrolysis by the Na+/K+ ATPase (sodium-potassium pump) is the phosphorylation of the pump. This phosphorylation is crucial for the pump's function, driving the conformational change necessary for ion transport across the cell membrane.

Question 19

Some cells express aquaporin proteins-they are channel proteins that facilitate the flow of water molecules through the plasma membrane.What regulates the rate and direction of water diffusion across the membrane?

Accepted Answer

The rate and direction of water diffusion across the membrane are regulated by solute concentrations on either side of the membrane. Water will diffuse from an area of low solute concentration to an area of high solute concentration in an effort to balance out the solute concentrations. This is known as osmosis. Aquaporin proteins only facilitate the movement of water molecules, they do not regulate the direction or rate of movement. Resting membrane potential and availability of ATP do not directly affect water diffusion.

Question 20

Ca²⁺-pumps in the plasma membrane and endoplasmic reticulum are important for

Accepted Answer

Ca²⁺-pumps help maintain low cytosolic Ca²⁺ concentrations, preventing it from interfering with cellular processes.

Quiz 12: Transport Across Cell Membranes

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following ions is the most abundant inside a typical mammalian cell?

Ion channels are classified as membrane transport proteins.They discriminate between ions based on size and charge.In addition to Na⁺, which one of the following ions would you expect to be able to freely diffuse through a Na⁺ channel? Explain your answer.

Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found?

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient.This type of transport is called

Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients.Which of the following is NOT one of the common ways to perform active transport?

Which of the following statements about resting membrane potential is FALSE?

Transporters, in contrast to channels, work by

Negatively charged ions are required to balance the net positive charge from metal ions such as K⁺, Na⁺, and Ca²⁺.Which of the following negatively charged ions is the most abundant outside the cell and which ion most often neutralize (written in parentheses) ?

Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules.In the extracellular case, what is the principal anion?

Which of the following statements is TRUE?

You have generated antibodies that recognize the extracellular domain of the Ca²⁺-pump.Adding these antibodies to animal cells blocks the active transport of Ca²⁺ from the cytosol into the extracellular environment.What do you expect to observe with respect to intracellular Ca²⁺?

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following negatively charged ions is NOT primarily used to buffer positive charges inside the cell?

Cells make use of H⁺ electrochemical gradients in many ways.Which of the following proton transporters is used to regulate pH in animal cells?

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following ions is the most abundant outside a typical mammalian cell?

Which of the following occur WITHOUT coupling transport of the solute to the movement of a second solute?

The Na⁺-K⁺ ATPase is also known as the Na⁺-K⁺ pump.It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration.What happens immediately after the pump hydrolyzes ATP?

Some cells express aquaporin proteins-they are channel proteins that facilitate the flow of water molecules through the plasma membrane.What regulates the rate and direction of water diffusion across the membrane?

Ca²⁺-pumps in the plasma membrane and endoplasmic reticulum are important for

Quiz 12: Transport Across Cell Membranes

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following ions is the most abundant inside a typical mammalian cell?

Ion channels are classified as membrane transport proteins.They discriminate between ions based on size and charge.In addition to Na+, which one of the following ions would you expect to be able to freely diffuse through a Na+ channel? Explain your answer.

Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found?

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient.This type of transport is called

Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients.Which of the following is NOT one of the common ways to perform active transport?

Which of the following statements about resting membrane potential is FALSE?

Transporters, in contrast to channels, work by

Negatively charged ions are required to balance the net positive charge from metal ions such as K+, Na+, and Ca2+.Which of the following negatively charged ions is the most abundant outside the cell and which ion most often neutralize (written in parentheses) ?

Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules.In the extracellular case, what is the principal anion?

Which of the following statements is TRUE?

You have generated antibodies that recognize the extracellular domain of the Ca2+-pump.Adding these antibodies to animal cells blocks the active transport of Ca2+ from the cytosol into the extracellular environment.What do you expect to observe with respect to intracellular Ca2+?

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following negatively charged ions is NOT primarily used to buffer positive charges inside the cell?

Cells make use of H+ electrochemical gradients in many ways.Which of the following proton transporters is used to regulate pH in animal cells?

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell.Which of the following ions is the most abundant outside a typical mammalian cell?

Which of the following occur WITHOUT coupling transport of the solute to the movement of a second solute?

The Na+-K+ ATPase is also known as the Na+-K+ pump.It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration.What happens immediately after the pump hydrolyzes ATP?

Some cells express aquaporin proteins-they are channel proteins that facilitate the flow of water molecules through the plasma membrane.What regulates the rate and direction of water diffusion across the membrane?

Ca2+-pumps in the plasma membrane and endoplasmic reticulum are important for

Ion channels are classified as membrane transport proteins.They discriminate between ions based on size and charge.In addition to Na⁺, which one of the following ions would you expect to be able to freely diffuse through a Na⁺ channel? Explain your answer.

Negatively charged ions are required to balance the net positive charge from metal ions such as K⁺, Na⁺, and Ca²⁺.Which of the following negatively charged ions is the most abundant outside the cell and which ion most often neutralize (written in parentheses) ?

You have generated antibodies that recognize the extracellular domain of the Ca²⁺-pump.Adding these antibodies to animal cells blocks the active transport of Ca²⁺ from the cytosol into the extracellular environment.What do you expect to observe with respect to intracellular Ca²⁺?

Cells make use of H⁺ electrochemical gradients in many ways.Which of the following proton transporters is used to regulate pH in animal cells?

The Na⁺-K⁺ ATPase is also known as the Na⁺-K⁺ pump.It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration.What happens immediately after the pump hydrolyzes ATP?

Ca²⁺-pumps in the plasma membrane and endoplasmic reticulum are important for