Question 1

Singer and Nicolson's fluid mosaic model of the membrane proposed that membranes

Accepted Answer

A)  are a phospholipid bilayer. 
B)  are a phospholipid bilayer between two layers of hydrophilic proteins. 
C)  are a single layer of phospholipids and proteins. 
D)  consist of protein molecules embedded in a fluid bilayer of phospholipids. 
E)  consist of a mosaic of polysaccharides and proteins. 
A)  are a phospholipid bilayer. 
B)  are a phospholipid bilayer between two layers of hydrophilic proteins. 
C)  are a single layer of phospholipids and proteins. 
D)  consist of protein molecules embedded in a fluid bilayer of phospholipids. 
E)  consist of a mosaic of polysaccharides and proteins.

Question 2

Which of the following would increase the electrochemical gradient across a membrane?

Accepted Answer

A)  a chloride channel 
B)  a sucrose-proton cotransporter 
C)  a proton pump 
D)  a potassium channel 
E)  both a proton pump and a potassium channel 
A)  a chloride channel 
B)  a sucrose-proton cotransporter 
C)  a proton pump 
D)  a potassium channel 
E)  both a proton pump and a potassium channel

Question 3

Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At high temperatures, these regions

Accepted Answer

A)  are more fluid than the surrounding membrane. 
B)  are less fluid than the surrounding membrane. 
C)  are able to flip from inside to outside. 
D)  detach from the plasma membrane and clog arteries. 
E)  have higher rates of lateral diffusion of lipids and proteins into and out of these regions. 
A)  are more fluid than the surrounding membrane. 
B)  are less fluid than the surrounding membrane. 
C)  are able to flip from inside to outside. 
D)  detach from the plasma membrane and clog arteries. 
E)  have higher rates of lateral diffusion of lipids and proteins into and out of these regions.

Question 4

Figure 5.2
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?

Accepted Answer

A)  The molarity of sucrose is higher than that of glucose on side A. 
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. 
A)  The molarity of sucrose is higher than that of glucose on side A. 
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.

Question 5

GTPase activity is important in the regulation of signal transduction because it

Accepted Answer

A)  increases the available concentration of phosphate. 
B)  decreases the amount of G protein in the membrane. 
C)  hydrolyzes GTP to GDP, thus shutting down the pathway. 
D)  converts cGMP to GTP. 
E)  phosphorylates protein kinases. 
A)  increases the available concentration of phosphate. 
B)  decreases the amount of G protein in the membrane. 
C)  hydrolyzes GTP to GDP, thus shutting down the pathway. 
D)  converts cGMP to GTP. 
E)  phosphorylates protein kinases.

Question 6

Which of the following is true of steroid receptors?

Accepted Answer

A)  The receptor molecules are themselves lipids or glycolipids. 
B)  The receptor may be inside the nuclear membrane. 
C)  The unbound steroid receptors are quickly recycled by lysosomes. 
D)  The concentration of steroid receptors must be relatively high in most cells. 
E)  The receptor molecules are free to move in and out of most organelles. 
A)  The receptor molecules are themselves lipids or glycolipids. 
B)  The receptor may be inside the nuclear membrane. 
C)  The unbound steroid receptors are quickly recycled by lysosomes. 
D)  The concentration of steroid receptors must be relatively high in most cells. 
E)  The receptor molecules are free to move in and out of most organelles.

Question 7

Figure 5.2
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.
-Initially, in terms of tonicity, the solution in side A with respect to that in side B is

Accepted Answer

A)  hypotonic. 
B)  plasmolyzed. 
C)  isotonic. 
D)  saturated. 
E)  hypertonic. 
A)  hypotonic. 
B)  plasmolyzed. 
C)  isotonic. 
D)  saturated. 
E)  hypertonic.

Question 8

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

Accepted Answer

A)  It is a peripheral membrane protein. 
B)  It exhibits a specificity for a particular type of molecule. 
C)  It requires the expenditure of cellular energy to function. 
D)  It works against diffusion. 
E)  It has few, if any, hydrophobic amino acids. 
A)  It is a peripheral membrane protein. 
B)  It exhibits a specificity for a particular type of molecule. 
C)  It requires the expenditure of cellular energy to function. 
D)  It works against diffusion. 
E)  It has few, if any, hydrophobic amino acids.

Question 9

Which of these are not embedded in the hydrophobic portion of the lipid bilayer?

Accepted Answer

A)  transmembrane proteins 
B)  integral proteins 
C)  peripheral proteins 
D)  integrins 
E)  glycoproteins 
A)  transmembrane proteins 
B)  integral proteins 
C)  peripheral proteins 
D)  integrins 
E)  glycoproteins

Question 10

Why are lipids and proteins free to move laterally in membranes?

Accepted Answer

A)  The interior of the membrane is filled with liquid water. 
B)  Lipids and proteins repulse each other in the membrane. 
C)  Hydrophilic portions of the lipids are in the interior of the membrane. 
D)  There are only weak hydrophobic interactions in the interior of the membrane. 
E)  Molecules such as cellulose can pull them in various directions. 
A)  The interior of the membrane is filled with liquid water. 
B)  Lipids and proteins repulse each other in the membrane. 
C)  Hydrophilic portions of the lipids are in the interior of the membrane. 
D)  There are only weak hydrophobic interactions in the interior of the membrane. 
E)  Molecules such as cellulose can pull them in various directions.

Question 11

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

Accepted Answer

A)  phospholipids and cellulose 
B)  nucleic acids and proteins 
C)  phospholipids and proteins 
D)  proteins and cellulose 
E)  glycoproteins and cholesterol 
A)  phospholipids and cellulose 
B)  nucleic acids and proteins 
C)  phospholipids and proteins 
D)  proteins and cellulose 
E)  glycoproteins and cholesterol

Question 12

Figure 5.4
Five dialysis bags, constructed from a semipermeable membrane that is 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.
-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?

Accepted Answer

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

Question 13

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that

Accepted Answer

A)  the integral membrane proteins are not strong enough to hold the bilayer together. 
B)  water that is present in the middle of the bilayer freezes and is easily fractured. 
C)  hydrophilic interactions between the opposite membrane surfaces are destroyed on freezing. 
D)  the carbon-carbon bonds of the phospholipid tails are easily broken. 
E)  the hydrophobic interactions that hold the membrane together are weakest at this point. 
A)  the integral membrane proteins are not strong enough to hold the bilayer together. 
B)  water that is present in the middle of the bilayer freezes and is easily fractured. 
C)  hydrophilic interactions between the opposite membrane surfaces are destroyed on freezing. 
D)  the carbon-carbon bonds of the phospholipid tails are easily broken. 
E)  the hydrophobic interactions that hold the membrane together are weakest at this point.

Question 14

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

Accepted Answer

A)  The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. 
B)  Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in their membranes. 
C)  Unsaturated fatty acids are more polar than saturated fatty acids. 
D)  The double bonds block interaction among the hydrophilic head groups of the lipids. 
E)  The double bonds result in shorter fatty acid tails and thinner membranes. 
A)  The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. 
B)  Unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in their membranes. 
C)  Unsaturated fatty acids are more polar than saturated fatty acids. 
D)  The double bonds block interaction among the hydrophilic head groups of the lipids. 
E)  The double bonds result in shorter fatty acid tails and thinner membranes.

Question 15

Which of the following statements is correct about diffusion?

Accepted Answer

A)  It is very rapid over long distances. 
B)  It requires an expenditure of energy by the cell. 
C)  It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. 
D)  It is an active process in which molecules move from a region of lower concentration to one of higher concentration. 
E)  It requires integral proteins in the cell membrane. 
A)  It is very rapid over long distances. 
B)  It requires an expenditure of energy by the cell. 
C)  It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. 
D)  It is an active process in which molecules move from a region of lower concentration to one of higher concentration. 
E)  It requires integral proteins in the cell membrane.

Question 16

Figure 5.3
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. Refer to the figure to answer the following questions.
-If you examine side A after three days, you should find

Accepted Answer

A)  a decrease in the concentration of NaCl and glucose and an increase in the water level. 
B)  a decrease in the concentration of NaCl, an increase in water level, and no change in the concentration of glucose. 
C)  no net change in the system. 
D)  a decrease in the concentration of NaCl and a decrease in the water level. 
E)  no change in the concentration of NaCl and glucose and an increase in the water level. 
A)  a decrease in the concentration of NaCl and glucose and an increase in the water level. 
B)  a decrease in the concentration of NaCl, an increase in water level, and no change in the concentration of glucose. 
C)  no net change in the system. 
D)  a decrease in the concentration of NaCl and a decrease in the water level. 
E)  no change in the concentration of NaCl and glucose and an increase in the water level.

Question 17

Which of the following membrane activities requires energy from ATP hydrolysis?

Accepted Answer

A)  facilitated diffusion of chloride ions across the membrane through a chloride channel 
B)  movement of water into a cell 
C)  movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid 
D)  movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell 
E)  movement of carbon dioxide out of a paramecium 
A)  facilitated diffusion of chloride ions across the membrane through a chloride channel 
B)  movement of water into a cell 
C)  movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid 
D)  movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell 
E)  movement of carbon dioxide out of a paramecium

Question 18

Figure 5.4
Five dialysis bags, constructed from a semipermeable membrane that is 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.
-Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?

Accepted Answer

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

Question 19

The cell membranes of Antarctic ice fish might have which of the following adaptations?

Accepted Answer

A)  very long chain fatty acids 
B)  branched isoprenoid lipids 
C)  a high percentage of polyunsaturated fatty acids 
D)  a higher percentage of trans fatty acids 
E)  no cholesterol 
A)  very long chain fatty acids 
B)  branched isoprenoid lipids 
C)  a high percentage of polyunsaturated fatty acids 
D)  a higher percentage of trans fatty acids 
E)  no cholesterol

Question 20

What is most likely to happen to an animal's target cells that lack receptors for local regulators?

Accepted Answer

A)  They might compensate by receiving nutrients via a factor. 
B)  They could develop normally in response to neurotransmitters instead. 
C)  They could divide but never reach full size. 
D)  They might not be able to multiply in response to growth factors from nearby cells. 
E)  Hormones would not be able to interact with target cells. 
A)  They might compensate by receiving nutrients via a factor. 
B)  They could develop normally in response to neurotransmitters instead. 
C)  They could divide but never reach full size. 
D)  They might not be able to multiply in response to growth factors from nearby cells. 
E)  Hormones would not be able to interact with target cells.

Exam 5: Membrane Transport and Cell Signaling

Singer and Nicolson's fluid mosaic model of the membrane proposed that membranes

Which of the following would increase the electrochemical gradient across a membrane?

Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. At high temperatures, these regions

GTPase activity is important in the regulation of signal transduction because it

Which of the following is true of steroid receptors?

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

Which of these are not embedded in the hydrophobic portion of the lipid bilayer?

Why are lipids and proteins free to move laterally in membranes?

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

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that

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

Which of the following statements is correct about diffusion?

Which of the following membrane activities requires energy from ATP hydrolysis?

The cell membranes of Antarctic ice fish might have which of the following adaptations?

What is most likely to happen to an animal's target cells that lack receptors for local regulators?

Introduction: Evolution and the Foundations of Biology

The Chemical Context of Life

Carbon and the Molecular Diversity of Life

A Tour of the Cell

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Chromosomal Basis of Inheritance

The Molecular Basis of Inheritance

Gene Expression: From Gene to Protein

Regulation of Gene Expression

Development, Stem Cells, and Cancer

Viruses

Genomes and Their Evolution

Descent With Modification

Phylogeny

The Evolution of Populations

The Origin of Species

Broad Patterns of Evolution

Early Life and the Diversification of Prokaryotes

The Origin and Diversification of Eukaryotes

The Colonization of Land by Plants and Fungi

The Rise of Animal Diversity

Plant Structure and Growth

Resource Acquisition, Nutrition, and Transport in Vascular Plants

Reproduction and Domestication of Flowering Plants

Plant Responses to Internal and External Signals

Homeostasis and Endocrine Signaling

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Reproduction and Development

Neurons, Synapses, and Signaling

Nervous and Sensory Systems

Motor Mechanisms and Behavior

Population Ecology and the Distribution of Organisms

Species Interactions

Ecosystems and Energy

Global Ecology and Conservation Biology

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