AP Biology Benchmark #6 Cell Membranes

1

According to the fluid mosaic model of cell membranes, phospholipids _____.

can move laterally along the plane of the membrane

frequently flip-flop from one side of the membrane to the other

have hydrophilic tails in the interior of the membrane

occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane

1

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose?

Permeability to glucose will stay the same.

Permeability will decrease initially then increase as the bilayer fills with glucose.

Permeability to glucose will increase.

Permeability to glucose will decrease.

1

Water passes quickly through cell membranes because

the bilayer is hydrophilic.

it moves through hydrophobic channels.

water movement is tied to ATP hydrolysis.

it is a small, polar, charged molecule.

it moves through aquaporins in the membrane.

The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half filled with a solution of 2 M sucrose and 1 M glucose. Side B is half filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal.

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1

Initially, in terms of tonicity, the solution in side A with respect to that in side B is

1

When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane?

There is directed movement of substances into and out of the cell.

There is no movement of substances into or out of the cell.

All movement of molecules across the plasma membrane occurs by active transport.

There is random movement of substances into and out of the cell.

1

Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?

Proteins only function on the cytoplasmic side of the cell membrane, which results in the membrane's asymmetrical nature.

The two sides of a cell membrane face different environments and carry out different functions.

Since the cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium, the membrane must be asymmetrical.

Since cell membranes communicate signals from one organism to another, the cell membranes must be asymmetrical.

1

A research team is working on the design of a new drug for the treatment of lung cancer. To be most effective, this drug must specifically enter the cytoplasm of lung cells while not entering the cells of other tissues. Which of the following characteristics would likely enhance the specificity of this drug?

specificity of the drug molecule for binding to the extracellular matrix of lung cells

phospholipid composition of lung cell plasma membranes

the relative hydrophobicity of the drug molecule

similarity of the drug molecule to other molecules normally transported into lung cells

1

Three lab groups carried out an experiment to identify the correct molarities for five solutions. Each unknown contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and 1.0 M. Each data entry represents the average of 3 sample replications of 1 cm3 sweet potato cubes expressed as percent change in mass after an overnight (24 hr) soak in the unknown solutions. From the data given, which statement most accurately describes what is occurring in response to a particular unknown solution.

Osmosis of water molecules from unknown solution A likely caused the increase in mass observed.

Unknown solution E contains the highest concentration of sucrose and the change in mass is due to the active transport of sucrose into the cell in exchange for water molecules.

Unknown solution C represents a sucrose molarity slightly lower than the molarity of sweet potato cells, thus water is transported out of the cells.

Passive transport of sucrose out of the potato cells explains the change in mass observed for unknown solution F.

Five dialysis bags, constructed of a type of membrane that is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed), and the percent change in mass of each bag was graphed.

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1

Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

A

B

C

D

Given: Potato cores are placed in sucrose solutions with various molar concentrations, and the percent change in calculated for each solution. The data is graphed. From this data, it is determined that the molar concentration of the potato is 0.32.

What you know:

The initial pressure potential = 0 (since we are doing the experiment in normal conditions with an open container)
Solute potential =-iCRT
The ionization constant (i) for sucrose: sucrose does not ionize in water
The experiment is assumed to be conducted at room temperature, 22 degrees celsius.

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1

What is the solute potential of the sucrose in the potato?

1

What is the overall water potential of the potato?

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1

Make a claim about what would happen to a plant that is watered using a 0.5 M sodium chloride solution instead of pure water.

2

Use evidence from the graph to support your claim. What solution shows a result similar to this scenario?

2

Provide reasoning for your claim. Use appropriate vocabulary terms.

An experiment is designed to study the mechanism of sucrose uptake by plant cells. Cells are immersed in a sucrose solution, and the pH of the solution is monitored. Samples of the cells are taken at intervals and their sucrose concentration is measured.

Initially, there is no change in the sucrose concentration inside of the cell. Then, the pH of the solution is observed to decrease until it reaches a steady, slightly acidic level. The sucrose concentration inside of the cell then begins to increase. The pH of the solution continues to remain at the slightly acidic level.

2

Evaluate these results and propose a general hypothesis to explain them.

6

Support your hypothesis by explaining the structures and concentrations involved in these results.

2

Predict what would happen if an inhibitor of ATP regeneration by the cell were added to the beaker once the pH was at the steady, slightly acidic level. Explain your answer.

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1

Describe the pattern of glucose uptake over time in guinea pig red blood cells.

1

AP Biology Benchmark #6 Cell Membranes

According to the fluid mosaic model of cell membranes, phospholipids _____.

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose?

Water passes quickly through cell membranes because

Initially, in terms of tonicity, the solution in side A with respect to that in side B is

When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane?

Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?

Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

What is the solute potential of the sucrose in the potato?

What is the overall water potential of the potato?

Make a claim about what would happen to a plant that is watered using a 0.5 M sodium chloride solution instead of pure water.

Use evidence from the graph to support your claim. What solution shows a result similar to this scenario?

Provide reasoning for your claim. Use appropriate vocabulary terms.

Evaluate these results and propose a general hypothesis to explain them.

Support your hypothesis by explaining the structures and concentrations involved in these results.

Predict what would happen if an inhibitor of ATP regeneration by the cell were added to the beaker once the pH was at the steady, slightly acidic level. Explain your answer.

Describe the pattern of glucose uptake over time in guinea pig red blood cells.

Propose a reasonable hypothesis to explain the difference in glucose uptake over time between the 2 guinea pigs in the experiment.

According to the fluid mosaic model of cell membranes, phospholipids _____.

A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose?

Water passes quickly through cell membranes because

Initially, in terms of tonicity, the solution in side A with respect to that in side B is

After the system reaches equilibrium, what changes are observed?

When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane?

Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?

Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

What is the solute potential of the sucrose in the potato?

What is the overall water potential of the potato?

Make a claim about what would happen to a plant that is watered using a 0.5 M sodium chloride solution instead of pure water.

Use evidence from the graph to support your claim. What solution shows a result similar to this scenario?

Provide reasoning for your claim. Use appropriate vocabulary terms.

Evaluate these results and propose a general hypothesis to explain them.

Support your hypothesis by explaining the structures and concentrations involved in these results.

Predict what would happen if an inhibitor of ATP regeneration by the cell were added to the beaker once the pH was at the steady, slightly acidic level. Explain your answer.

Describe the pattern of glucose uptake over time in guinea pig red blood cells.

Propose a reasonable hypothesis to explain the difference in glucose uptake over time between the 2 guinea pigs in the experiment.

After the system reaches equilibrium, what changes are observed?