Quiz 4: Membrane Structure and Function; Chapter 7 Campbell Biology

___________ is the diffusion of free water across a selectively permeable membrane.

Osmosis

The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy is called a. Active transport b. Passive transport c. Diffusion d. Facilitated diffusion

a. Active transport

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? a. Permeability to glucose will increase. b. Permeability to glucose will decrease. c. Permeability to glucose will stay the same. d. Permeability will decrease initially then increase as the bilayer fills with glucose.

a. Permeability to glucose will increase.

The solutions in the arms of a U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. In the U-tube experiment illustrated above, which of the following statements correctly describes side B at equilibrium? a. The concentration of NaCl and glucose will decrease, and the water level will increase. b. The concentration of NaCl will increase, the concentration of glucose will decrease, and the water level will increase c. The concentration of NaCl will increase, the concentration of glucose will decrease, and the water level will decrease d. The concentration of NaCl and glucose will increase, and the water level will decrease

a. The concentration of NaCl and glucose will decrease, and the water level will increase.

According to the fluid mosaic model of cell membranes, phospholipids ________. a. can move laterally along the plane of the membrane b. frequently flip-flop from one side of the membrane to the other c. occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane d. have hydrophilic tails in the interior of the membrane

a. can move laterally along the plane of the membrane

The membranes of winter wheat are able to remain fluid when it is extremely cold by ________. a. increasing the proportion of unsaturated phospholipids in the membrane b. decreasing the percentage of cholesterol molecules in the membrane c. decreasing the number of hydrophobic proteins in the membrane d. increasing the proportion of glycolipids in the membrane

a. increasing the proportion of unsaturated phospholipids 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. Before diffusion and osmosis takes place, the liquid levels on both sides are equal; therefore, in the U-tube illustrated above, with respect to sucrose alone ________. a. side A is hypertonic to side B b. side A is hypotonic to side B c. side A is isotonic to side B d. side A is more turgid than side B

a. side A is hypertonic to side B

Based on the data provided, the intracellular molarity of dissolved solutes in sweet potato cells is approximately ________. a. 0.2M b. 0.4M c. 0.6M d. 0.8M

b. 0.4M

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 weighed, and the percent change in mass of each bag was graphed. Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes? a. A and B b. B c. D d. D and E

b. B

For a plant cell in surroundings where there is a tendency for water to leave the plant cell, the plant cell is called _________________. a. Turgid b. Flaccid c. Plasmolyzed d. Lysed

b. Flaccid

Three lab groups carried out an experiment to identify the concentration of sucrose in six 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. Cubes of sweet potato (1 cm3) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry in the table below represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. From the data given, which statement most accurately describes what is occurring in response to a particular unknown solution? a. Unknown solution E contains the highest concentration of sucrose, and the change in mass is due to the active transport of sucrose out of the cell. b. Osmosis of water molecules from unknown solution B likely caused the increase in mass observed. c. Passive transport of sucrose out of the potato cells explains the change in mass observed for unknown solution F. d. Unknown solution C represents a sucrose concentration slightly higher than the molarity of sweet potato cells, thus water is transported out of the cells.

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

When a plant cell, such as one from a tulip leaf, is submerged in a hypertonic solution, what is likely to occur? a. The cell will burst b. Plasmolysis will shrink the interior of the cell c. The cell will become flaccid d. The cell will become turgid

b. Plasmolysis will shrink the interior of the cell

What kinds of molecules pass through a cell membrane most easily? a. Lsrge and hydrophobic b. Small and hydrophobic c. Large polar d. Small and ionic

b. Small and hydrophobic

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. Which of the following will be true when the system illustrated above reaches equilibrium? a. The concentration of sucrose on side A will be greater than the concentration of sucrose on side B. b. The water level will be higher in side A than in side B. c. The water levels will be unchanged. d. The water level will be higher in side B than in side A.

b. The water level will be higher in side A than in side B.

When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane? a. There is directed movement of substances into and out of the cell. b. There is random movement of substances into and out of the cell. c. There is no movement of substances into or out of the cell. d. All movement of molecules across the plasma membrane occurs by active transport

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

A swollen or distended cell, as in plant cells are called _________________. a. Lysed b. Turgid c. Flaccid d. Plasmolyzed

b. Turgid

Amphipathic describes ______________________________. a. a region along which the density of a chemical substance increases or decrease b. a molecule having both a hydrophilic region and a hydrophobic region. c. one of many types of secreted chemicals that are formed in specialized cells, which travels in body fluids and acts on specific target cells in other parts of the organism, changing the target cells functioning. d. a molecule that binds specifically to another molecule, usually a larger one.

b. a molecule having both a hydrophilic region and a hydrophobic region.

The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditures, is called ______________________. a. Active transport b. facilitated diffusion c. passive transport d. diffusion

b. facilitated diffusion

The property of biological membranes that allows them to regulate the passage of substances across them is called ____________________________. a. amphipathic. b. selective permeability. c. second messenger d. signal transduction.

b. selective permeability.

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. A b. B c. C d. D

c. C

Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes? a. The soium-potassium pump b. Aquaporins c. Gated ion channels d. ATP

c. Gated ion channels

Which of the following statements correctly describes osmosis? a. Osmosis only takes place in red blood cells. b. Osmosis is an energy-demanding or "active" process. c. In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration. d. In osmosis, solutes move across a membrane from areas of lower water concentration to areas of higher water concentration.

c. In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.

For a protein to be an integral membrane protein, it would have to be ________. a. Hydrophilic b. Hydrophobic c. amphipathic, with at least one hydrophobic region d. exposed on only one surface of the membrane

c. amphipathic, with at least one hydrophobic region

Peripheral proteins are __________________________________. a. proteins that open or close channels in response to a particular stimulus. b. proteins that allow a specific ion to diffuse across the membrane down its concentration or electrochemical gradient. c. proteins loosely bound to the surface of a membrane or to a part of an integral protein and not embedded in the lipid layer. d. proteins with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane.

c. proteins loosely bound to the surface of a membrane or to a part of an integral protein and not embedded in the lipid layer.

The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy is called ______________________. a. Diffusion b. Passive transport c. Facilitated diffusion d. Active transport

d. Active transport

Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature? a. Since the cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium, the membrane must be asymmetrical. b. Since cell membranes communicate signals from one organism to another, the cell membranes must be asymmetrical. c. The two sides of a cell membrane face different environments and carry out different functions. d. Proteins only function on the cytoplasmic side of the cell membrane, which results in the membrane's asymmetrical nature.

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

Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures? a. Unsaturated fatty acids have a higher cholesterol content, which prevents adjacent lipids from packing tightly. b. Unsaturated fatty acids are more nonpolar than saturated fatty acids. c. The double bonds block interaction among the hydrophilic head groups of the lipids. d. The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly

d. The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly

Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following types of treatments? a. antiviral medications that are efficient and work well with most viruses b. intravenous feeding techniques c. medications to slow blood loss d. hydrating drinks with high concentrations of salt and glucose

d. hydrating drinks with high concentrations of salt and glucose

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? a. the relative hydrophobicity of the drug molecule b. phospholipid composition of lung cell plasma membranes c. specificity of the drug molecule for binding to the extracellular matrix of lung cells d. similarity of the drug molecule to other molecules normally transported in to lung cells

d. similarity of the drug molecule to other molecules normally transported in to lung cells

A swollen or distended cell, as in plant cells are called _________________. a. Plasmolyzed b. Flaccid c. lysed d. turgid

d. turgid

The ____________ is the currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids.

fluid mosaic model

A _________________ solution refers to a solution that, when surrounding a cell, will cause the cell to lose water.

hypertonic

A ___________ _solution refers to a solution that, when surrounding a cell, will cause the cell to gain water.

hypotonic

A ________________ solution refers to a solution that, when surrounding a cell, will cause no net movement of water into or out of a cell.

isotonic