BIO 121 Chapter 7: Membrane Structure and Function-Study Guide

14) The presence of cholesterol in the plasma membranes of some animals: A) Enables the membrane to stay fluid more easily when cell temperature drops. B) Enables the animal to remove hydrogen atoms from saturated phospholipids. C) Enables the animal to add hydrogen atoms to unsaturated phospholipids. D) Makes the membrane less flexible, allowing it to sustain greater pressure from within the cell. E) Makes the animal more susceptible to circulatory disorders.

A

19) Which component is a protein fiber of the extracellular matrix? A) A B) B C) C D) E

A

22) Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures? A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. B) Unsaturated fatty acids have higher cholesterol content and therefore more cholesterol in 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

25) Which of the following factors would tend to increase membrane fluidity? A) A greater proportion of unsaturated phospholipids. B) A greater proportion of saturated phospholipids. C) A lower temperature. D) Relatively high protein content in the membrane. E) A greater proportion of relatively large glycolipids compared with lipids having smaller

A

28) A protein that spans the phospholipid bilayer one or more times is: A) A transmembrane protein. B) An integral protein. C) A peripheral protein. D) An integrin. E) A glycoprotein.

A

3) You have a planar bilayer with equal amounts of saturated and unsaturated phospholipids. After testing the permeability of this membrane to glucose, you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to 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) You cannot predict the outcome. You simply have to make the measurement.

A

34) Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly? A) CO2. B) An amino acid. C) Glucose. D) K+. E) Starch.

A

38) Nitrous oxide gas molecules diffusing across a cell's plasma membrane is an example of: A) Diffusion across the lipid bilayer. B) Facilitated diffusion. C) Active transport. D) Osmosis. E) Co-transport.

A

4) According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids? A) They can move laterally along the plane of the membrane. B) They frequently flip-flop from one side of the membrane to the other. C) They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane. D) They are free to depart from the membrane and dissolve in the surrounding solution. E) They have hydrophilic tails in the interior of the membrane.

A

40) When a cell is in equilibrium with its environment, which of the following occurs for substances that can diffuse through the cell? A) There is random movement of substances into and out of the cell. B) There is directed movement of substances into and out of the cell. C) There is no movement of substances into and out of the cell. D) All movement of molecules is directed by active transport.

A

41) Which of the following is true of 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.

A

55) 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: A) Co-transport proteins. B) Ion channels. C) Carrier proteins. D) Passive diffusion across the plasma membrane. E) Cellular metabolic reactions that create or destroy ions.

A

6) Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold? A) By increasing the percentage of unsaturated phospholipids in the membrane. B) By increasing the percentage of cholesterol molecules in the membrane. C) By decreasing the number of hydrophobic proteins in the membrane. D) By cotransport of glucose and hydrogen. E) By using active transport.

A

21) Which component is a glycolipid? A) A B) B C) C D) E

B

26) In what way do the membranes of a eukaryotic cell vary? A) Phospholipids are found only in certain membranes. B) Certain proteins are unique to each membrane. C) Only certain membranes of the cell are selectively permeable. D) Only certain membranes are constructed from amphipathic molecules. E) Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm.

B

29) What kinds of molecules pass through a cell membrane most easily? A) Large and hydrophobic. B) Small and hydrophobic. C) Large polar. D) Ionic. E) Monosaccharides such as glucose.

B

31) Which of the following is a characteristic feature of a carrier protein in a plasma membrane? A) It is a peripheral membrane protein. B) It exhibits 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.

B

45) In which of the following would there be the greatest need for osmoregulation? A) An animal connective tissue cell bathed in isotonic body fluid. B) A salmon moving from a river into an ocean. C) A red blood cell surrounded by plasma. D) A lymphocyte before it has been taken back into lymph fluid. E) A plant being grown hydroponically in a watery mixture of designated nutrients.

B

47) A sodium-potassium pump: A) Moves three potassium ions out of a cell and two sodium ions into a cell while producing an ATP for each cycle. B) Move three sodium ions out of a cell and two potassium ions into a cell while consuming an ATP for each cycle. C) Moves three potassium ions out of a cell and two sodium ions into a cell while consuming 2 ATP in each cycle. D) Move three sodium ions out of a cell and two potassium ions into a cell and generates an ATP in each cycle.

B

49) Which of the following membrane activities requires energy from ATP? A) Facilitated diffusion of chloride ions across the membrane through a chloride channel. B) Movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid. C) Movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell. D) Movement of carbon dioxide out of a paramecium.

B

52) Which of the following would increase the electrochemical gradient across a membrane? A) A sucrose-proton cotransporter. B) A proton pump. C) A potassium channel. D) Both a proton pump and a potassium channel.

B

57) Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean? A) Proton pumps must have evolved before any living organisms were present on Earth. B) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life. C) The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism. D) Cells of each domain evolved proton pumps independently when oceans became more acidic. E) Proton pumps are necessary to all cell membranes.

B

59) The force driving simple diffusion is _____, while the energy source for active transport is _____. A) The concentration gradient; ADP. B) The concentration gradient; ATP. C) Transmembrane pumps; electron transport. D) Phosphorylated protein carriers; ATP.

B

7) Some regions of the plasma membrane, called lipid rafts, have a higher concentration of cholesterol molecules. As a result, these lipid rafts: A) Are more fluid than the surrounding membrane. B) Are more rigid (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 the lipid rafts.

B

9) An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function? A) Transporting ions against an electrochemical gradient. B) Cell-cell recognition. C) Maintaining fluidity of the phospholipid bilayer. D) Attaching to the cytoskeleton. E) Establishing the diffusion barrier to charged molecules.

B

10) Which of these are NOT embedded in the hydrophobic portion of the lipid bilayer at all? A) Transmembrane proteins. B) Integral proteins. C) Peripheral proteins. D) Integrins. E) Glycoproteins.

C

12) Which of the following types of molecules are the major structural components of the cell membrane? A) Phospholipids and cellulose. B) Nucleic acids and proteins. C) Phospholipids and proteins. D) Proteins and cellulose. E) Glycoproteins and cholesterol.

C

15) In order 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) Completely covered with phospholipids. E) Exposed on only one surface of the membrane.

C

2) 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

20) Which component is a microfilament (actin filament) of the cytoskeleton? A) A B) B C) C D) D

C

23) Which of the following is true of integral membrane proteins? A) They lack tertiary structure. B) They are loosely bound to the surface of the bilayer. C) They are usually transmembrane proteins. D) They are not mobile within the bilayer. E) They serve only a structural role in membranes.

C

24) Cell membranes are asymmetrical. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature? A) The cell membrane forms a border between one cell and another in tightly packed tissues such as epithelium. B) Cell membranes communicate signals from one organism to another. C) The two sides of a cell membrane face different environments and carry out different functions. D) The "innerness" and "outerness" of membrane surfaces are predetermined by genes. E) Proteins can only be associated with the cell membranes on the cytoplasmic side.

C

37) Which of the following statements is correct about diffusion? 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.

C

42) Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the fresh water: A) And the salt solutions are both hypertonic to the cells of the celery stalks. B) Is hypotonic and the salt solution is hypertonic to the cells of the celery stalks. C) Is hypertonic and the salt solution is hypotonic to the cells of the celery stalks. D) Is isotonic and the salt solution is hypertonic to the cells of the celery stalks.

C

43) 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? A) The cell would shrink because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. B) The cell would shrink because the water in the beaker is hypertonic relative to the cytoplasm of the RBC. C) The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. D) The cell will remain the same size because the solution outside the cell is isotonic.

C

48) The sodium-potassium pump is called an electrogenic pump because it: A) Pumps equal quantities of Na+ and K+ across the membrane. B) Pumps hydrogen ions out of the cell. C) Contributes to the membrane potential. D) Ionizes sodium and potassium atoms. E) Is used to drive the transport of other molecules against a concentration gradient.

C

5) According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly A) Spread in a continuous layer over the inner and outer surfaces of the membrane. B) Confined to the hydrophobic interior of the membrane. C) Embedded in a lipid bilayer. D) Randomly oriented in the membrane, with no fixed inside-outside polarity. E) Free to depart from the fluid membrane and dissolve in the surrounding solution.

C

50) What is the voltage across a membrane called? A) Water potential. B) Chemical gradient. C) Membrane potential. D) Osmotic potential. E) Electrochemical gradient.

C

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

D

16) 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: A) Peripheral proteins. B) Phospholipids. C) Carbohydrates. D) Integral proteins. E) Cholesterol molecules.

D

17) Which component is a peripheral protein? A) A B) B C) C D) D

D

30) Which of the following most accurately describes selective permeability? A) An input of energy is required for transport. B) Lipid-soluble molecules pass through a membrane. C) There must be a concentration gradient for molecules to pass through a membrane. D) Only certain molecules can cross a cell membrane.

D

32) 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.

D

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

D

35) Which of the following allows water to move much faster across cell membranes? A) The sodium-potassium pump. B) ATP. C) Peripheral proteins. D) Aquaporins.

D

36) You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells? A) Blood or tissue type of the patient. B) Hydrophobicity of the drug molecule. C) Lack of charge on the drug molecule. D) Similarity of the drug molecule to other molecules transported by the target cells. E) Lipid composition of the target cells' plasma membrane.

D

60) An organism with a cell wall would most likely be unable to take in materials through: A) Diffusion. B) Osmosis. C) Active transport. D) Phagocytosis. E) Facilitated diffusion.

D

39) Which of the following processes includes all others? A) Osmosis. B) Diffusion of a solute across a membrane. C) Facilitated diffusion. D) Passive transport. E) Transport of an ion down its electrochemical gradient.

D

44) Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells? A) The animal cell is in a hypotonic solution, and the plant cell is in an isotonic solution. B) The animal cell is in an isotonic solution, and the plant cell is in a hypertonic solution. C) The animal cell is in a hypertonic solution, and the plant cell is in an isotonic solution. D) The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution. E) The animal cell is in a hypertonic solution, and the plant cell is in a hypotonic solution.

D

51) Ions diffuse across membranes through specific ion channels: A) Down their chemical gradients. B) Down their concentration gradients. C) Down the electrical gradients. D) Down their electrochemical gradients. E) Down the osmotic potential gradients.

D

8) Singer and Nicolson's fluid mosaic model of the membrane proposed that: A) Membranes are a phospholipid bilayer. B) Membranes are a phospholipid bilayer between two layers of hydrophilic proteins. C) Membranes are a single layer of phospholipids and proteins. D) Membranes consist of protein molecules embedded in a fluid bilayer of phospholipids. E) Membranes consist of a mosaic of polysaccharides and proteins.

D

1) Who was/were the first to propose that cell membranes are phospholipid bilayers? A) H. Davson and J. Danielli. B) I. Langmuir. C) C. Overton. D) S. Singer and G. Nicolson. E) E. Gorter and F. Grendel.

E

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: 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.

E

18) Which component is cholesterol? A) B B) C C) D D) E

E

27) The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is: A) To facilitate diffusion of molecules down their concentration gradients. B) To actively transport molecules against their concentration gradients. C) To maintain the integrity of a fluid mosaic membrane. D) To maintain membrane fluidity at low temperatures. E) To mediate cell-to-cell recognition.

E

46) When a plant cell, such as one from a rose stem, is submerged in a very hypotonic solution, what is likely to occur? A) The cell will burst. B) The cell membrane will lyse. C) Plasmolysis will shrink the interior. D) The cell will become flaccid. E) The cell will become turgid.

E

53) The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane-more acidic outside the cell than inside the cell. Phosphate transport is an example of: A) Passive diffusion. B) Facilitated diffusion. C) Active transport. D) Osmosis. E) Co-transport.

E

54) Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells? A) Simple diffusion. B) Phagocytosis. C) Active transport pumps. D) Exocytosis. E) Facilitated diffusion.

E

56) Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal? A) The sodium ions are moving down their electrochemical gradient while glucose is moving up. B) Glucose entering the cell along its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient. C) Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell. D) The cotransporter can also transport potassium ions. E) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.

E

58) 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? A) Antiviral medications that are efficient and work well with all viruses. B) Antibiotics against the viruses in question. C) Intravenous feeding techniques. D) Medication to prevent blood loss. E) Hydrating drinks that include high concentrations of salts and glucose.

E