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Exam 7: Membrane Structure and Function

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Question 31

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Which of the following is true of the evolution of cell membranes?

A) Cell membranes have stopped evolving now that they are fluid mosaics.
B) Cell membranes cannot evolve if the membrane proteins do not.
C) The evolution of cell membranes is driven by the evolution of glycoproteins and glycolipids.
D) All components of membranes evolve in response to natural selection.
E) An individual organism selects its preferred type of cell membrane for particular functions.

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

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Question 32

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Use the following information to answer the questions below. 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. -After the system reaches equilibrium,what changes are observed?

A) The molarity of sucrose and glucose are equal on both sides.
B) The molarity of glucose is higher in side A than in side B.
C) The water level is higher in side A than in side B.
D) The water level is unchanged.
E) The water level is higher in side B than in side A.

F) B) and D)
G) A) and D)

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Question 33

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For the following questions,match the labelled component of the cell membrane in the figure with its description. -Which component is cholesterol?

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

In most cells,there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane.The gradients of the other ions are most likely accounted for by

Use the following information to answer the questions below. Cystic fibrosis is a genetic disease in humans in which the CFTR protein,which functions as a chloride ion channel,is missing or nonfunctional in cell membranes. -In the small airways of the lung,a thin layer of liquid is needed between the epithelial cells and the mucus layer in order for cilia to beat and move the mucus and trapped particles out of the lung.One hypothesis is that the volume of this airway surface liquid is regulated osmotically by transport of sodium and chloride ions across the epithelial cell membrane.How would the lack of a functional chloride channel in cystic fibrosis patients affect sodium ion transport and the volume of the airway surface liquid?

Fibronectin binds to integrin,an integral plasma membrane protein.Binding of fibronectin to the extracellular domain of integrin changes integrin's conformation.The change in protein conformation is transmitted to the cytoplasm resulting in a cascade of reactions.What does this description describe?

According to the fluid mosaic model of membrane structure,proteins of the membrane are mostly

Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?

Use the following information to answer the questions below. Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface molecules.The viral nucleic acid molecules are enclosed in a protein capsid,and the protein capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral glycoproteins.One hypothesis for viral entry into cells is that binding of HIV membrane glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma membrane,releasing the viral capsid into the cytoplasm.An alternative hypothesis is that HIV gains entry into the cell via receptor-mediated endocytosis,and membrane fusion occurs in the endocytotic vesicle.To test these alternative hypotheses for HIV entry,researchers labelled the lipids on the HIV membrane with a red fluorescent dye. -If HIV first enters the cell in an endocytotic vesicle,instead of directly fusing with the plasma membrane,then

When a membrane is freeze-fractured,the bilayer splits down the middle between the two layers of phospholipids.In an electron micrograph of a freeze-fractured membrane,the bumps seen on the fractured surface of the membrane are

-What will happen to a red blood cell (RBC) ,which has an internal ion concentration of about 0.9 percent,if it is placed into a beaker of pure water?

Which of the following types of molecules are the major structural components of the cell membrane?

For the following questions,match the labelled component of the cell membrane in the figure with its description. -Which component is the peripheral protein?

Cell membranes are asymmetrical.Which of the following is the most likely explanation?

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

Water passes quickly through cell membranes because

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?

Mammalian blood contains the equivalent of 0.15 M NaCl.Seawater contains the equivalent of 0.45 M NaCl.What will happen if red blood cells are transferred to seawater?

An organism non-selectively takes in droplets of water and small molecules.What is this process called?