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1. The compounds in biological membranes that form a barrier to the movement of hydrophilic materials across the membrane are
2. Biological membranes are composed of
3. Which of the following statements about the proteins of the plasma membrane and the proteins of the inner mitochondrial membrane is true?
e. The two membranes differ in their lipid composition.
4. The plasma membrane of animals contains carbohydrates
b. on the outer side of the membrane, protruding into the environment.
5. In biological membranes, the phospholipids are arranged in a
a. bilayer, with the fatty acids pointing toward each other.
6. Cholesterol molecules act to
e. alter the fluidity of the membrane.
7. Peripheral membrane proteins have
e. polar regions that interact with similar regions of integral membrane proteins.
8. The functional roles for different proteins found in membranes include all except
e. stabilizing the lipid bilayer.
9. Houseplants adapted to indoor temperatures may die when accidentally left outdoors in the cold because their
b. membranes lack adequate fluidity.
10. A protein that forms an ion channel through a membrane is most likely to be
b. a transmembrane protein.
11. The hydrophilic regions of a membrane protein are most likely to be found
d. exposed on the surface of the membrane.
12. A characteristic of plasma membranes that helps them fuse during vesicle formation and phagocytosis is the
b. capacity of lipids to associate and maintain a bilayer organization.
13. The plasma membranes of winter wheat are able to remain fluid when it is extremely cold by
d. replacing saturated fatty acids with unsaturated fatty acids.
14. Which type of membrane protein would likely be most easily removed in a laboratory experiment?
c. Peripheral proteins
15. 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.
16. 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
17. 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.
18. When vesicles from the Golgi apparatus deliver their contents to the exterior of the cell, they add their membranes to the plasma membrane. The plasma membrane does not increase in size, because
c. membrane is continually being lost from the plasma membrane by endocytosis.
19. Protein movement within a membrane may be restricted by
c. the cytoskeleton and lipid rafts.
20. Which of the following functions as a recognition signal for interactions between cells?
21. 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
22. Which of the following are not specialized cell junctions?
d. Cytoplasmic plaques
23. Muscle cells recognize and adhere to one another because of specific membrane proteins called
b. cell adhesion molecules.
24. Cell growth can involve movement of membrane material from
b. the Golgi apparatus to the cell membrane.
25. The difference between tight junctions, desmosomes, and gap junctions is that
c. tight junctions and desmosomes have mechanical roles, whereas gap junctions facilitate communication between cells.
26. Desmosomes include or associate with
a. dense plaque-like regions.
b. keratin fibers.
c. external cell adhesion molecules.
27. Structures that contain networks of keratin fibers and provide mechanical stability to epithelial tissues are called
28. The electric signal for a contraction passes rapidly from one muscle cell to the next by way of
c. gap junctions.
29. Specialized channel proteins called connexons occur in
e. gap junctions.
30. Which of the following statements about diffusion is false?
e. Simple diffusion depends upon specific carrier proteins.
31. Which of the following is an example of passive transport?
a. Facilitated diffusion
32. Which of the following does not affect the rate of diffusion of a substance?
d. Presence of other substances in the solution
33. A concentration gradient of glucose across a membrane means that
b. glucose molecules are more crowded on one side of the membrane than on the other.
34. When placed in water, wilted plants lose their limpness because of
c. osmosis of water into the plant cells.
35. The difference between osmosis and diffusion is that
d. osmosis refers to the movement of water, whereas diffusion is the movement of molecules.
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?
b. The red and green inks will be uniformly distributed throughout the pan.
37. Osmosis is a specific form of
38. Osmosis moves water from a region of _______ to a region of _______.
b. low concentration of dissolved material; high concentration of dissolved material
39. Which of the following molecules is the most likely to diffuse across a cell membrane?
c. A steroid
40. When a severely dehydrated patient is brought to the hospital, an IV of normal saline is started immediately. Distilled water is not used because
c. it would cause blood cells to swell and eventually burst.
41. When placed in a hypertonic solution, animal cells
a. helps cells maintain turgor pressure in plants.
43. If a red blood cell is placed in an isotonic solution,
e. water moves into and out of the cell at an equal rate.
44. The speed and direction of ions as they move into and out of the cell are determined by the
b. concentration gradient and electrochemical imbalances.
45. 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.
46. 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.
47. How does an ion channel exert its specificity for one ion and not another?
e. The ion lets go of its water and is attracted to a channel pore protein.
48. Water crosses the plasma membrane at a rate faster than expected due to
a. hydration of the ions as they pass through.
b. water channels called aquaporins.
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 because
c. the carrier proteins are saturated.
51. Active transport usually moves molecules
b. in the opposite direction in which diffusion moves them.
52. Secondary active transport involves all of the following except
a. the direct use of ATP.
53. Amino acids enter cells against their concentration gradients by means of
d. secondary active transport.
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 symport.
55. Plant cells transport sucrose across the vacuole membrane against its concentration gradient by a process known as
b. a symport.
56. 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
e. an antiport.
57. The only process that can bring glucose molecules into cells and does not involve the metabolic energy of ATP is
58. For each molecule of ATP consumed during active transport of sodium and potassium,
d. two K+ ions are imported and three Na+ ions are exported.
59. Receptor-mediated endocytosis is the mechanism for transport of
60. Phagocytosis, pinocytosis, and receptor-mediated endocytosis all involve
b. invagination of the plasma membrane.
61. Which of the following processes does not involve the uptake of materials into the cell?
62. Persons with the inherited disease familial hypercholesterolemia have very high levels of cholesterol because of
c. deficient LDL receptor proteins.
63. 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 functiond. Conduction of nerve impulses
64. An important function of specialized membranes found in certain organelles is to
c. transform energy.
1. The study of the spread and control of disease is called _______.
2. Most of the lipids composing biological membranes are called _______.
3. Biological membranes are composed of a continuous phospholipid bilayer in which proteins are embedded. This general design is known as the _______ model.
4. Lipids can move _______, however, they seldom move across the bilayers of a biological membrane.
5. Membrane proteins covalently bonded to carbohydrates are called _______.
6. Membrane lipids covalently bonded to carbohydrates are called _______.
7. Membrane segments synthesized on the ER move to other points of the cell as _______.
8. Cell adhesion molecules of the same type are called _______.
9. Cell adhesion molecules that are responsible for mammalian egg and sperm cells binding to one another are referred to as _______.
10. 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 _______.
11. The processes of cell recognition and cell adhesion are dependent upon _______ proteins.
12. _______ is the process of random movement toward a state of equilibrium.
13. The ability of some materials to move through biological membranes more readily than through others is called _______.
14. Diffusion is the net movement of particles from regions of _______ concentration to regions of _______ concentration.
15. If a cell placed within a solution shrinks, the solution is _______ relative to the cell.
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.
17. The coupled transport system by which glucose and sodium ions simultaneously enter intestinal epithelial cells is called _______.
18. The sodium–potassium pump of cell membranes is an example of a coupled transport called a(n) _______.
19. _______ involves coated pits, clathrin, and coated vesicles.
20. The process by which the plasma membrane engulfs large particles or even whole cells is called _______.
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