Chapter 6: Cell Membranes

Alzheimer's disease

1. Learning about the formation and operation of plasma membranes may give scientists insights into a disease characterized by plaques and extreme forgetfulness called _______.

c. lipids.

1. The compounds in biological membranes that form a barrier to the movement of hydrophilic materials across the membrane are a. integral membrane proteins. b. carbohydrates. c. lipids. d. nucleic acids. e. peripheral membrane proteins.

d. replacing saturated fatty acids with unsaturated fatty acids.

10. The plasma membranes of winter wheat are able to remain fluid when it is extremely cold by a. increasing the number of cholesterol molecules present. b. closing protein channels. c. decreasing the number of hydrophobic proteins present. d. replacing saturated fatty acids with unsaturated fatty acids. e. using fatty acids with longer tails.

integral

10. The processes of cell recognition and cell adhesion are dependent upon _______ proteins.

tight junction

11. The cells of the intestinal epithelium are linked together in order to prevent substances from passing between them. The type of cell junction linking these cells is called a _______.

c. Peripheral proteins

11. Which type of membrane protein would likely be most easily removed in a laboratory experiment? a. Integral proteins b. Channel proteins c. Peripheral proteins d. Transmembrane proteins e. Gated channels

c. hydrophobic.

12. The LDL receptor is an integral protein that crosses the plasma membrane, with portions of the protein extending both outside and into the interior of the cell. The amino acid side chains (R groups) in the region of the protein that crosses the membrane are most likely a. charged. b. hydrophilic. c. hydrophobic. d. carbohydrates. e. lipids.

diffusion

12. The process of random movement of molecules toward a state of equilibrium is called _______.

selective permeability

13. The ability of some materials to move through biological membranes more readily than through others is called _______.

a. the capacity of lipids to associate with one another.

13. When vesicles from the Golgi apparatus deliver their contents to the exterior of the cell, they add their membranes to the existing plasma membrane. This is made possible by a. the capacity of lipids to associate with one another. b. the fact that saturated fatty acid chains allow for close packing of fatty acids in the bilayer. c. the great affinity cholesterol molecules in the plasma membrane have for fatty acid tails. d. the polar proteins' affinity for fatty acids. e. the noncovalent interactions of the anchored membrane proteins.

greater; lesser

14. Diffusion is the net movement of particles from regions of _______ concentration to regions of _______ concentration.

e. Stabilizing the lipid bilayer

14. Which of the following is not one of the functional roles of membrane proteins? a. Allowing movement of molecules that otherwise would be excluded by the lipid components of the membrane b. Transferring signals from outside the cell to inside the cell c. Maintaining the shape of the cell d. Facilitating the transport of macromolecules across the membrane e. Stabilizing the lipid bilayer

b. a transmembrane protein.

15. A protein that forms an ion channel through a membrane is most likely to be a. a peripheral protein. b. a transmembrane protein. c. a phospholipid. d. an enzyme. e. entirely outside the phospholipid bilayer.

hypertonic

15. If a cell placed within a solution shrinks, the solution is _______ relative to the cell.

d. exposed on the surface of the membrane.

16. The hydrophilic regions of a membrane protein are most likely to be found a. only in muscle cell membranes. b. associated with the fatty acid region of the lipids. c. in the interior of the membrane. d. exposed on the surface of the membrane. e. either on the surface or inserted into the interior of the membrane.

turgor

16. When plant cells are placed in a hypotonic solution, water enters the cells and exerts pressure against the cell wall. This force is called _______ pressure.

symport

17. The coupled transport system by which glucose and sodium ions simultaneously enter intestinal epithelial cells is called _______.

a. many proteins can move around within the bilayer.

17. When a mouse cell and a human cell are fused, the membrane proteins of the two cells become uniformly distributed over the surface of the hybrid cell. This occurs because a. many proteins can move around within the bilayer. b. all proteins are anchored within the membrane. c. proteins are asymmetrically distributed within the membrane. d. all proteins in the plasma membrane are peripheral. e. different membranes contain different proteins.

antiporter

18. The sodium-potassium pump of cell membranes is an example of a coupled transport called a(n) _______.

a. integral membrane proteins.

18. When a membrane is prepared by freeze-fracture and examined under the electron microscope, the exposed interior of the membrane bilayer appears to be covered with bumps. These bumps are a. integral membrane proteins. b. ice crystals. c. platinum. d. organelles. e. vesicles.

c. the cytoskeleton.

19. Protein movement within a membrane may be restricted by a. glycolipids and glycoproteins. b. closure of gated channels. c. the cytoskeleton. d. cell adhesion. e. tight junctions and desmosomes.

receptor-mediated endocytosis

19. The process of _______ involves coated pits, clathrin, and coated vesicles.

phospholipids

2. Most of the lipids composing biological membranes are called _______.

b. on the outer side of the membrane, protruding into the environment.

2. The plasma membrane of animals contains carbohydrates a. on the inner side of the membrane, facing the cytosol. b. on the outer side of the membrane, protruding into the environment. c. on both sides of the membrane. d. on neither side of the membrane. e. within the membrane.

phagocytosis

20. The process by which the plasma membrane engulfs large particles or even whole cells is called _______.

a. Rough ER, Golgi apparatus, vesicle, plasma membrane

20. Which of the following represents the correct pathway for the synthesis and secretion of insulin, a protein secreted by the cells of the pancreas? a. Rough ER, Golgi apparatus, vesicle, plasma membrane b. Golgi apparatus, rough ER, lysosome c. Lysosome, vesicle, plasma membrane d. Plasma membrane, coated vesicle, lysosome e. Rough ER, cytoplasm, plasma membrane

e. Glycolipids

21. Which of the following functions as a recognition signal for interactions between cells? a. RNA b. Phospholipids c. Cholesterol d. Fatty acids e. Glycolipids

b. cell adhesion molecules.

22. Muscle cells recognize and adhere to one another because of specific membrane proteins called a. coated vesicles. b. cell adhesion molecules. c. glycolipids. d. carrier molecules. e. transport proteins.

d. Cytoplasmic plaques

23. Which of the following are not specialized cell junctions? a. Gap junctions b. Tight junctions c. Desmosomes d. Cytoplasmic plaques e. Both a and b

c. tight junctions and desmosomes have mechanical roles, whereas gap junctions facilitate communication between cells.

24. The difference between tight junctions, desmosomes, and gap junctions is that a. desmosomes and gap junctions contain keratin, whereas tight junctions have collagen. b. gap junctions and tight junctions have specialized protein channels called connexons, whereas desmosomes do not. c. tight junctions and desmosomes have mechanical roles, whereas gap junctions facilitate communication between cells. d. desmosomes and gap junctions are found in epithelial tissue, whereas tight junctions are found in nerve cells. e. they all have different functions, even though their structure is the same.

a. integrins.

25. A group of transmembrane proteins involved in maintaining cell structure via their interactions with the cytoskeletion are being studied to determine their role in the spread of cancer. These proteins are known as a. integrins. b. desmosomes. c. seal tissues. d. connexins. e. keratins.

e. All of the above

26. Desmosomes include or associate with a. dense, plaquelike regions. b. keratin fibers. c. external cell adhesion molecules. d. Both a and b e. All of the above

d. desmosomes.

27. Structures that contain networks of keratin fibers and provide mechanical stability to epithelial tissues are called a. extracellular matrices. b. glycoproteins. c. gap junctions. d. desmosomes. e. phospholipid bilayers.

c. gap junctions.

28. The electric signal for a contraction passes rapidly from one muscle cell to the next by way of a. tight junctions. b. desmosomes. c. gap junctions. d. integral membrane proteins. e. freeze-fractures.

e. gap junctions.

29. Specialized channel proteins called connexons occur in a. the cytoskeleton. b. tight junctions. c. desmosomes. d. plasmodesmata. e. gap junctions.

e. lipids, proteins, and carbohydrates.

3. Biological membranes are composed of a. nucleotides and nucleosides. b. enzymes, electron acceptors, and electron donors. c. fatty acids. d. monosaccharides. e. lipids, proteins, and carbohydrates.

fluid mosaic

3. Biological membranes are composed of a continuous phospholipid bilayer in which proteins are embedded. This general design is known as the _______ model.

e. Simple diffusion depends upon specific carrier proteins.

30. Which of the following statements about diffusion is false? a. Diffusion depends on the intrinsic kinetic energy of molecules. b. Diffusion continues until the concentrations are in equilibrium. c. In diffusion, molecules move from areas of greater concentration to areas of lesser concentration. d. Diffusion is a random process. e. Simple diffusion depends upon specific carrier proteins.

d. Presence of other substances in the solution

31. Which of the following does not affect the rate of diffusion of a substance? a. Temperature of the solution b. Concentration gradient c. Distance traveled d. Presence of other substances in the solution e. Molecular diameter of the diffusing material

a. Facilitated diffusion

32. Which of the following is an example of passive transport? a. Facilitated diffusion b. The sodium-potassium pump c. Phagocytosis d. Exocytosis e. Pinocytosis

b. glucose molecules are more crowded on one side of the membrane than on the other.

33. A concentration gradient of glucose across a membrane means that a. there are more moles of glucose on one side of the membrane than on the other. b. glucose molecules are more crowded on one side of the membrane than on the other. c. there is less water on one side of the membrane than on the other. d. the glucose molecules are chemically more tightly bonded on one side than on the other. e. there are more glucose molecules within the membrane than outside the membrane.

c. A steroid

34. Which of the following molecules is the most likely to diffuse across a cell membrane? a. Glucose b. Na+ c. A steroid d. A common amino acid e. Cl-

d. osmosis refers specifically to the movement of water, whereas diffusion is the movement of molecules.

35. The difference between osmosis and diffusion is that a. diffusion is passive transport, whereas osmosis is active transport. b. only in diffusion do molecules move from areas of high concentrations to areas of low concentration. c. only diffusion refers to the movement of materials across a semipermeable membrane. d. osmosis refers specifically to the movement of water, whereas diffusion is the movement of molecules. e. the process of osmosis varies according to the kinds of particles present.

b. The red and green inks will be uniformly distributed throughout the pan.

36. If a shallow pan is filled with water, a drop of red ink is placed in one end of the pan, and a drop of green ink is placed in the other end, which of the following will be true at equilibrium? a. The red ink will be uniformly distributed in one half of the pan, and the green ink will be uniformly distributed in the other half of the pan. b. The red and green inks will be uniformly distributed throughout the pan. c. Each ink will move down its concentration gradient. d. The concentration of each ink will be higher at one end of the pan than at the other end. e. No predictions can be made without knowing the molecular weights of the pigment molecules.

a. diffusion.

37. Osmosis is a specific form of a. diffusion. b. facilitated transport. c. active transport. d. secondary active transport. e. movement of water by carrier proteins.

b. low concentration of dissolved material; high concentration of dissolved material

38. Osmosis moves water from a region of _______ to a region of _______. a. high concentration of dissolved material; low concentration of dissolved material b. low concentration of dissolved material; high concentration of dissolved material c. hypertonic solution; hypotonic solution d. negative osmotic potential; positive osmotic potential e. low concentration of water; high concentration of water

a. helps cells maintain turgor pressure in plants.

39. Osmosis a. helps cells maintain turgor pressure in plants. b. moves macromolecules from one cell to another. c. facilitates the "flipping" of proteins from one side of the membrane to the other. d. keeps concentrations uniform in all cells. e. regulates the membrane potential of the cell.

a. bilayer; fatty acids pointing toward each other

4. In biological membranes, the phospholipids are arranged in a _______, with the _______. a. bilayer; fatty acids pointing toward each other b. bilayer; fatty acids facing outward c. single layer; fatty acids facing the interior of the cell d. single layer; phosphorus-containing region facing the interior of the cell e. bilayer; phosphorus groups in the interior of the membrane

lateral

4. Lipids can move in a _______ direction, although they seldom move across the bilayers of a biological membrane.

c. osmosis of water into the plant cells.

40. When placed in water, wilted plants lose their limpness because of a. active transport of salts from the water into the plant cells. b. active transport of salts into the water from the plant cells. c. osmosis of water into the plant cells. d. osmosis of water from the plant cells. e. diffusion of water from the plant cells.

c. it would cause the patient's blood cells to swell and eventually burst.

41. When a severely dehydrated patient is brought to the hospital, an IV of normal saline is started immediately. Distilled water is not used because a. it would cause water to leave the cells of the patient and the cells would collapse. b. nutrients are provided by the saline. c. it would cause the patient's blood cells to swell and eventually burst. d. normal saline is more economical. e. the distilled water might be contaminated by bacteria.

a. shrink.

42. When placed in a hypertonic solution, animal cells a. shrink. b. swell. c. burst. d. transport water out. e. concentrate.

e. take up and release water at an equal rate.

43. If a red blood cell is placed in an isotonic solution, it will a. shrivel. b. swell and burst. c. shrivel and then return to normal. d. swell and then return to normal. e. take up and release water at an equal rate.

e. All of the above

44. Which of the following statements about channel proteins is true? a. They have a central pore of polar amino acids and water. b. They are anchored in the hydrophobic bilayer of the plasma membrane. c. They are surrounded by nonpolar amino acids. d. They are usually gated. e. All of the above

a. a charge imbalance across the plasma membrane.

45. One result of the movement of ions through ion channels is the creation of a membrane potential. The membrane potential is a. a charge imbalance across the plasma membrane. b. the difference in ion concentrations on either side of the plasma membrane. c. the difference in ATP concentrations on either side of the plasma membrane. d. the capacity for active transport. e. the ability of macromolecules to recognize and adhere to one another.

b. concentration gradient and electrochemical imbalances.

46. The speed and direction of ions as they move into and out of the cell are determined by the a. ability of the ion to let go of its water. b. concentration gradient and electrochemical imbalances. c. number of channel proteins present. d. size and charge of the ion. e. presence of specific stimuli to open gated channel proteins.

e. The ion lets go of its water and is attracted to a channel pore protein.

47. How does an ion channel exert its specificity for one ion and not another? a. It is a simple matter of charge and ionic size. b. The ion channel hydrates ions as they pass through. c. The ion channel makes use of aquaporins. d. There are recognition sites in the ion channel. e. The ion lets go of its water and is attracted to a channel pore protein.

d. Both a and b

48. Water crosses the plasma membrane at a rate faster than expected for simple diffusion because of a. the hydration of the ions as they pass through. b. water channels called aquaporins. c. gated channels. d. Both a and b e. All of the above

a. Facilitated diffusion via a carrier protein

49. In a hypothetical study, cells are placed in a solution of glucose in which the concentration of glucose is gradually increased. At first, the rate at which glucose enters the cells is found to increase as the concentration of the glucose solution is increased. But when the glucose concentration of the solution is increased above 10 M, the rate no longer increases. Which of the following is the likely mechanism for glucose transport into these cells? a. Facilitated diffusion via a carrier protein b. Facilitated diffusion via a channel protein c. Pinocytosis d. Secondary active transport e. A symporter

vesicles

5. Membrane segments synthesized on the ER move to other points of the cell in the form of _______.

e. The two membranes differ in their lipid composition.

5. Which of the following statements about the proteins of the plasma membrane and the proteins of the inner mitochondrial membrane is true? a. Both membranes have only peripheral proteins. b. Only the mitochondrial membrane has integral proteins. c. Only the mitochondrial membrane has peripheral proteins. d. All of the proteins from both membranes are hydrophilic. e. The two membranes differ in their lipid composition.

c. the carrier proteins are saturated.

50. In facilitated diffusion, the diffusion rate of a specific molecule across a membrane does not continue to increase as the concentration difference of the molecule across the membrane increases. This is the case because a. facilitated diffusion requires the use of ATP. b. as the concentration difference increases, molecules interfere with one another. c. the carrier proteins are saturated. d. the transport protein must be of the channel type. e. the diffusion constant depends on the concentration difference.

b. in a direction opposite to the one in which diffusion moves them.

51. Active transport usually moves molecules a. in the same direction as diffusion moves them. b. in a direction opposite to the one in which diffusion moves them. c. in a direction that tends to bring about equilibrium. d. toward higher pH. e. toward higher osmotic potential.

b. active transport.

52. Plant cells transport sucrose across the vacuole membrane against its concentration gradient by a process known as a. simple diffusion. b. active transport. c. passive transport. d. facilitated diffusion. e. cellular respiration.

a. The direct use of ATP

53. Which of the following is not involved in secondary active transport? a. The direct use of ATP b. Coupling to another transport system c. Use of an existing concentration gradient d. The plasma membrane e. The ability to concentrate the transported molecule

a. a symporter.

54. In the intestine, Na+ and an amino acid bind to the same transport protein that moves the two substances in the same direction. This type of active transport is called a. a symporter. b. an antiporter. c. secondary active transport. d. facilitated transport. e. a diffusion mechanism.

e. an antiporter.

55. In the parietal cells of the stomach, the uptake of chloride ions is coupled to the transport of bicarbonate ions out of the cell. This type of transport system is called a. a uniporter. b. a symporter. c. an exchange channel. d. diffusion. e. an antiporter.

d. secondary active transport.

56. Amino acids enter cells against their concentration gradients by means of a. simple diffusion. b. facilitated diffusion. c. primary active transport. d. secondary active transport. e. osmosis.

d. two K+; three Na+

57. For each molecule of ATP consumed during active transport of sodium and potassium, there is an import of _______ ion(s) and an export of _______ ion(s). a. two Na+; three K+ b. two Na+; one K+ c. one K+; three Na+ d. two K+; three Na+ e. three K+; two Na+

d. diffusion.

58. The only process that can bring glucose molecules into cells that does not involve the metabolic energy of ATP is a. phagocytosis. b. pinocytosis. c. active transport. d. diffusion. e. osmosis.

d. cholesterol.

59. Receptor-mediated endocytosis is the mechanism for transport of a. clathrin. b. all macromolecules. c. ions. d. cholesterol. e. integral membrane proteins.

glycoproteins

6. Membrane proteins covalently bonded to carbohydrates are called _______.

e. They alter the fluidity of the membrane.

6. Which of the following statements about cholesterol molecules is true? a. They help hold a membrane together. b. They transport ions across membranes. c. They attach to carbohydrates. d. They disrupt membrane function. e. They alter the fluidity of the membrane.

b. invagination of the plasma membrane.

60. Phagocytosis, pinocytosis, and receptor-mediated endocytosis all involve a. the intake of large particles. b. invagination of the plasma membrane. c. the export of macromolecules. d. the presence of receptor proteins. e. the intake of fluids by the cell.

a. Exocytosis

61. Which of the following processes does not involve the uptake of materials into the cell? a. Exocytosis b. Pinocytosis c. Endocytosis d. Receptor-mediated endocytosis e. Phagocytsis

c. deficient LDL receptor proteins.

62. Persons with the inherited disease familial hypercholesterolemia have very high levels of cholesterol because of a. hyperactive aquaporins. b. the inability to hydrolysize ATP. c. deficient LDL receptor proteins. d. malformed gap junctions. e. defective ion channels.

c. transform energy.

63. An important function of specialized membranes found in certain organelles is to a. help the organelles move. b. protect the organelles from increased temperatures. c. transform energy. d. make use of the cells' internal genetic information. e. destroy cellular waste products.

e. All of the above are functions of plasma membranes.

64. Which of the following is not a function of plasma membranes? a. Conversion of glucose energy to ATP b. Arrangement of enzymes c. Turning off of a specific cell function d. Conduction of nerve impulses e. All of the above are functions of plasma membranes.

glycolipids

7. Membrane lipids covalently bonded to carbohydrates are called _______.

e. Their polar regions interact with similar regions of integral membrane proteins.

7. Which of the following statements about peripheral membrane proteins is true? a. They have hydrophobic regions within the lipid portion of the bilayer. b. They have hydrophilic regions that protrude in aqueous environments on either side of the membrane. c. They move laterally but not vertically within the bilayer. d. They control the rate of diffusion. e. Their polar regions interact with similar regions of integral membrane proteins.

homotypic

8. Cell adhesion molecules of the same type are called _______.

b. membranes lack adequate fluidity.

8. Houseplants adapted to indoor temperatures may die if they are left outdoors, because in a cold environment their a. DNA cannot function. b. membranes lack adequate fluidity. c. photosynthesis is impaired. d. chloroplasts malfunction. e. membranes need more cholesterol.

b. capacity of lipids to associate and maintain a bilayer organization.

9. A characteristic of plasma membranes that helps them fuse during vesicle formation and phagocytosis is the a. ratio of one protein molecule for every 25 phospholipid molecules. b. capacity of lipids to associate and maintain a bilayer organization. c. constant fatty acid chain length and degree of saturation. d. ability of phospholipid molecules to flip over and trade places with other phospholipid molecules. e. asymmetrical distribution of membrane proteins.

heterotypic

9. Cell adhesion molecules that are responsible for the binding together of mammalian egg and sperm cells are referred to as _______.