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The fluid nature of the membranes is attributed to a lateral movement of


A) protein channels.
B) phospholipid molecules.
C) antigen molecules.
D) pumps such as the proton pump.
E) the entire lipid bilayer.

F) B) and E)
G) C) and E)

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The diagram shows the rate of diffusion into a cell using carrier proteins. The diagram shows the rate of diffusion into a cell using carrier proteins.    McGraw-Hill Education -The rate of diffusion will increase as A) the number of glucose molecules decreases. B) the number of glucose molecules increases. C) temperature decreases. D) pH rises. McGraw-Hill Education -The rate of diffusion will increase as


A) the number of glucose molecules decreases.
B) the number of glucose molecules increases.
C) temperature decreases.
D) pH rises.

E) A) and B)
F) All of the above

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A phospholipid molecule has a polar and a nonpolar end.Because of this,water molecules form


A) polar bonds with the nonpolar end of the phospholipid molecule.
B) polar bonds with the polar end of the phospholipid molecule.
C) hydrogen bonds with the nonpolar end of the phospholipid molecule.
D) hydrogen bonds with the polar end of the phospholipid molecule.
E) covalent bonds with the nonpolar end of the phospholipid molecule.

F) None of the above
G) C) and D)

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A dehydrated runner drinks a lot of water after a race.He or she rehydrates because


A) the contents of the digestive tract are hypotonic compared to the bloodstream.
B) the bloodstream is hypotonic compared to the contents of the digestive tract.
C) the contents of the digestive tract and the bloodstream are isotonic compared to each other.
D) water will diffuse from an area where its concentration is low to an area where its concentration is high.

E) All of the above
F) A) and D)

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The rate of diffusion of molecules would be fastest in a cell with an


A) internal concentration of 45 percent and an external concentration of 50 percent in cold temperatures.
B) internal concentration of 50 percent and an external concentration of 12 percent in cold temperatures.
C) internal concentration of 50 percent and an external concentration of 12 percent in warm temperatures.
D) internal concentration of 40 percent and an external concentration of 35 percent in warm temperatures.

E) A) and C)
F) B) and C)

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Facilitated diffusion is an important method for cells in obtaining necessary molecules and removing other ones.Requirements for facilitated diffusion include


A) The carrier molecule must be specific to the molecule that is transported.The direction of movement is always with the concentration gradient,never against the gradient.
B) The carrier molecule is nonspecific to the molecule that is transported.The direction of movement is always with the concentration gradient,never against the gradient.
C) The carrier molecule is nonspecific to the molecule that is transported.The direction of movement is always against the concentration gradient,never with the gradient.
D) The carrier molecule must be specific to the molecule that is transported and an ATP molecule must be attached to the specific carrier.The direction of movement is always against the concentration gradient,never with the gradient.

E) C) and D)
F) All of the above

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One day during the summer you and some friends make ice cream using an electric ice cream maker.To get the ice cream to form,a mixture of salt and ice is packed around the ice cream maker.A few days later you notice a yellow circle of dead grass where the ice cream maker had been placed.You hypothesize that some of the salt and ice mixture spilled onto the grass and ________.


A) froze the grass
B) was isosmotic to the grass cells causing the yellow circle of dead grass
C) was hyperosmotic to the grass cells causing the yellow circle of dead grass
D) was hypoosmotic to the grass cells causing the yellow circle of dead grass

E) A) and B)
F) B) and C)

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The type of movement that is specific and requires carrier molecules and energy is


A) exocytosis.
B) facilitated diffusion.
C) active transport.
D) endocytosis.
E) osmosis.

F) All of the above
G) A) and E)

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The diagram shows the rate of diffusion into a cell using carrier proteins. The diagram shows the rate of diffusion into a cell using carrier proteins.    McGraw-Hill Education -If Na<sup>+</sup> levels were depleted in the extracellular fluid,rate of glucose movement would A) increase. B) decrease. C) stay the same. McGraw-Hill Education -If Na+ levels were depleted in the extracellular fluid,rate of glucose movement would


A) increase.
B) decrease.
C) stay the same.

D) A) and B)
E) A) and C)

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Incubation of cells at 20°C blocks the release of proteins from the trans-Golgi.Under such conditions,you would expect to see


A) an increase in exocytosis.
B) a decrease in exocytosis.
C) an increase in endocytosis.
D) a decrease in endocytosis.

E) None of the above
F) B) and C)

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Cholesterol is a structural component of cell membranes.Amount of cholesterol present can affect membrane stability and permeability.What is the role of cholesterol in a membrane?


A) A membrane that needs to be more rigid and more permeable,would have high cholesterol ratios.
B) A membrane that needs to be rigid,such as a protective barrier,would have low cholesterol ratios.
C) Membranes with low amounts of cholesterol are very stable and have increased permeability.
D) Membranes with high amounts of cholesterol are very stable and have decreased permeability.

E) B) and D)
F) B) and C)

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Cholesterol functions in the plasma membrane to


A) transport ions.
B) serve as an energy molecule.
C) maintain fluidity.
D) mediate steroid action.
E) maintain hypertension.

F) All of the above
G) A) and C)

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If a cell has the same concentration of dissolved molecules as its outside environment,the cell's condition is referred to as being


A) isotonic.
B) hypertonic.
C) hypotonic.
D) hydrophobic.
E) hydrophilic.

F) A) and E)
G) A) and D)

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A scientist performs an experiment in which they create an artificial cell with a selectively permeable membrane through which only water can pass.They inject a 5M solution of glucose into the cell and then place the cell into a beaker of water.After an hour,what effect do you expect to observe?


A) Water moves out of the cell
B) Glucose moves out of the cell
C) No net change in cell weight
D) Water moves into the cell
E) Glucose moves into the cell

F) None of the above
G) A) and E)

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The fluid mosaic model proposed by Singer and Nicolson in 1972 explained that


A) the cell membrane was composed of lipids and proteins.
B) the cell membrane was composed of a phospholipid bilayer between two layers of globular proteins.
C) the cell membrane was composed of a phospholipid bilayer with globular proteins actually inserted into the bilayer.
D) the cell membrane was composed of a phospholipid bilayer but the polar ends of the phospholipid molecules were reversed.

E) None of the above
F) All of the above

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Membrane fluidity is affected by


A) temperature,cholesterol,types of fatty acids.
B) size of molecules,polarity of molecules,temperature.
C) types of fatty acids,waters affinity for hydrogen bonding.
D) hyrophillic tails,hydrophobic heads,cholesterol.

E) None of the above
F) A) and D)

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Cyclodextrins are a group of compounds capable of removing cholesterol from membranes.The effect most likely to have a large impact on cells as a result of cyclodextrin treatment would be


A) increased concentration of transmembrane proteins.
B) increased permeability of the membrane.
C) increased membrane fluidity at lower temperatures.
D) increased membrane fluidity at higher temperatures.
E) disruption of transmembrane protein structure.

F) B) and D)
G) None of the above

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If ATP production is blocked,decreased transport of material across a membrane occurs.Which type of transport is affected? Choose all that apply.


A) Osmosis
B) Diffusion
C) Facilitated Diffusion
D) Active Transport
E) Endocytosis

F) A) and C)
G) A) and B)

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To test for the presence of starch,iodine can be used.A positive reaction results in a black color.A dialysis bag filled with starch solution and secured on both ends is placed in iodine solution.After 30 minutes the dialysis bag appears black.Based on this information,what most accurately describes what happened?


A) Due to its size and polarity,starch was able to exit the dialysis bag and interact with the iodine solution.
B) Due to its size and polarity,iodine was able to enter the dialysis bag and interact with starch.
C) Over time,both iodine and starch are equally distributed throughout the two solutions.

D) B) and C)
E) None of the above

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A novice gardener notices that many plants in his garden look wilted.What osmotic solution would you suggest the novice gardener use to best return the plants to full health?


A) Place the plants in a 15% solute solution so water can be actively transported out of the plant cells.
B) Place the plants in a 5% solute solution so water can be actively transported out of the plant cells.
C) Place the plants in a 5% solute solution so water can diffuse into the plant cells.
D) Place the plants in a 15% solute solution so water can diffuse out of the plant cells.

E) C) and D)
F) None of the above

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