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The pKa of the weak base ammonia NH3 is 9.25. What pH value is most likely to be that of the inside (lumen) of the lysosome?
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 _______.
1. In the 1920s, circumstantial evidence indicated that DNA was the genetic material. Which of the following experiments led to the acceptance of this hypothesis?
a. Griffith’s experiments with Streptococcus pneumoniae
b. Avery, MacLeod, and McCarty’s work with isolating the transforming principle
c. Hershey and Chase’s experiments with viruses and radioisotopes
2. In Griffith’s experiments, when heat-killed S strain pneumococci were injected into a mouse along with live R strain pneumococci,
b. DNA from the heat-killed S was taken up by the live R, converting the latter to S and killing the mouse.
3. Experiments designed to identify the transforming principle were based on
c. selectively destroying the different macromolecules in a cell-free extract.
4. Griffith’s experiment with pneumococcus demonstrated that
c. materials from dead organisms can affect and change living organisms.
5. Griffith was able to distinguish the two strains of pneumococcus by means of
a. the appearance of the colonies in culture.
b. differences in their lethality in mice.
6. In order to show that DNA is the “transforming principle,” Avery, MacLeod, and McCarty showed that DNA could transform nonvirulent strains of pneumococcus. Their hypothesis was strengthened by their demonstration that
b. enzymes that destroy nucleic acids also destroy transforming activity.
7. The Hershey–Chase experiment
d. helped prove that DNA is the genetic molecule.
8. Before the discovery of DNA, the hereditary material was thought to be made of proteins and not nucleic acids because
c. proteins seemed to be much more chemically diverse.
9. The Hershey–Chase experiment persuaded most scientists that
b. DNA is indeed the carrier of hereditary information.
10. During infection of E. coli cells by bacteriophage T2,
d. only nucleic acids enter the cell.
11. Bacteriophage nucleic acids were labeled by carrying out an infection of E. coli cells growing in
c. 32P-labeled phosphate.
12. If Hershey and Chase had found 35S in both the pellet and the supernatant, what would have been their likely conclusion about the nature of DNA replication?
b. No conclusion would have been possible from these results.
13. The Hershey–Chase experiment determined that
d. DNA, not protein, is the hereditary material of viruses.
14. Which of the following molecules functions to transfer information from one generation to the next in eukaryotes?
15. The rules formulated by Erwin Chargaff state that
a. A = T and G = C in any molecule of DNA.
16. Purines include
e. adenine and guanine.
17. Information sources used by Watson and Crick to determine the structure of DNA included
e. X-ray crystallography of double-stranded DNA.
18. If a double-stranded DNA molecule contains 30 percent T, it must contain _______ percent G.
19. The base composition of DNA isolated from a newly discovered virus is found to be 32 percent A, 17 percent C, 32 percent G, and 19 percent T. What would be a reasonable explanation for this observation?
d. The genome of the phage is single-stranded, not double-stranded.
20. The DNA isolated from a newly discovered virus is found to be 32 percent A, 17 percent C, 32 percent G, and 19 percent T. The base composition of the complementary DNA would be _______ percent A, _______ percent C, _______ percent G, and _______ percent T.
b. 19; 32; 17; 32
21. Which feature of the Watson–Crick model of DNA structure explains its ability to function in replication and gene expression?
a. Each strand contains all the information present in the double helix.
22. Chargaff’s rule states that
e. the amount of cytosine equals the amount of guanine.
23. A deoxyribose nucleotide is a
c. deoxyribose plus a nitrogenous base and a phosphate.
25. The structure of the DNA molecule was determined by the experiments of
26. Which of the following molecular models describes the structure of the DNA molecule?
e. Helical, double-stranded, and antiparallel
27. Double-stranded DNA looks a little like a ladder that has been twisted into a helix, or spiral. The side supports of the ladder are
d. alternating sugars and phosphates.
28. The steps of the ladder are
b. pairs of bases.
29. The structure of DNA is characterized by a
b. right-handed double helix and antiparallel strands.
30. The characteristic of DNA that allows it to make an exact copy of itself is its
b. complementary base pairing.
31. The nitrogenous bases (and the two strands of the DNA double helix) are held together by
c. hydrogen bonds.
32. Which of the following statements about the molecular architecture of DNA is true?
a. The two strands run in opposite directions.
b. The molecule’s twist is right-handed.
c. The molecule is a double-stranded helix.
d. It has a uniform diameter.
33. What accounts for the uniform diameter of the DNA molecule?
b. A purine always bonds with a pyrimidine.
34. The strands that make up DNA are antiparallel. This means that
c. the 5’ to 3’ direction of one strand is counter to the 5’ to 3’ direction of the other strand.
35. The antiparallel relationship of the two strands of DNA refers to the
c. alignment of the strands, such that one strand starts with a 3’ carbon and the other starts with a 5’ carbon.
36. The force of _______ holds DNA together in a double helix.
e. hydrogen bonds
37. Which one of the following is not found in DNA?
38. Although DNA is made up of only four different bases, it can encode the information necessary to specify the workings of an entire organism because DNA
a. molecules are extremely long.
39. The structure of DNA explains which three major properties of genes?
e. They contain information, replicate exactly, and can change to produce a mutation.
40. Mutations are
b. heritable changes in the sequence of DNA bases.
41. The first scientist(s) to suggest a mode of replication for DNA was (were)
d. Watson and Crick.
42. A deoxyribose nucleoside is a
a. deoxyribose plus a nitrogenous base.
43. Kornberg showed that new DNA molecules can be synthesized in a test tube containing deoxyribose
c. nucleoside triphosphates.
44. At the end of DNA replication, two DNA molecules are produced, each one consisting of a parental DNA strand and a new DNA strand. This process is known as
a. semiconservative replication.
45. In the Meselson–Stahl experiment, the conservative model of DNA replication was ruled out by which of the following observations?
a. No completely “heavy” DNA was observed after the first round of replication.
46. During DNA replication
b. the template strands must separate so that both can be copied.
47. If Meselson and Stahl had observed one intermediate, slightly smeared band after growing bacteria for one generation, and then after two generations again had found one slightly smeared band, they would most likely have concluded that DNA replicates
48. In DNA replication, each newly made strand is
b. complementary in sequence to the strand from which it was copied.
49. Semiconservative replication of DNA involves
a. each of the original strands acting as a template for a new strand.
50. In a growing DNA strand, each monomer is added to which carbon of the deoxyribose?
51. During replication, the new DNA strand is synthesized
b. in the 5’ to 3’ direction.
52. DNA replication in eukaryotes differs from replication in bacteria because
c. there are many replication forks in each eukaryotic chromosome and only one in bacterial DNA.
53. In eukaryotic cells, each chromosome has
c. many origins of replication.
54. The energy necessary for making a DNA molecule comes directly from the
c. release of phosphates.
55. Pyrophosphate is a
b. by-product of DNA synthesis.
56. DNA polymerase lengthens a polynucleotide strand by
d. covalently linking new nucleotides to a previously existing strand.
57. Why is RNA incorporated into the DNA molecule during DNA replication?
d. DNA polymerases can only add on to an existing strand.
58. The molecules that function to replicate DNA in the cell are
b. DNA polymerases.
59. Which of the following is the correct order of events for synthesis of the lagging strand?
a. Primase adds RNA primer, DNA polymerase III creates a stretch, DNA polymerase I removes the primer, and ligase seals the gaps.
60. Fragments like those now called Okazaki fragments were expected even before they were discovered because
b. the replication fork moves forward along a double-stranded DNA molecule.
61. In eukaryotes, Okazaki fragments are about _______ base pairs long.
62. The enzyme DNA ligase is required continuously during DNA replication because
b. fragments of the lagging strand must be joined together.
63. In bacteria, the enzyme that removes the RNA primers is called
e. DNA polymerase I
64. The enzyme that restores the phosphodiester linkage between adjacent fragments in the lagging strand during DNA replication is
a. DNA ligase.
65. The enzyme that unwinds the DNA prior to replication is called
66. Fourteen human DNA polymerases have been identified. Which of the following statements about them is true?
e. Only one of the fourteen is involved in DNA replication; the others are involved in primer removal and DNA repair.
67. Why don’t cells last the entire lifetime of an organism?
a. The removal of the RNA primer following DNA replication leads to a shortening of the chromosome and eventual cell death.
68. In the cells of prokaryotes, methylated guanine contributes to
e. correcting of mismatched pairs of bases.
69. The first repair of mistakes during DNA replication is made by
b. DNA polymerase.
70. The error rate of changing an incorrect base with another incorrect base during proofreading is one in _______ bases.
71. The fidelity of DNA replication is astounding. During DNA synthesis, the error rate is on the order of one wrong nucleotide per
72. In PCR, _______ creates single-stranded DNA template molecules.
73. Ideally, PCR _______ increases the amount of DNA during additional cycles.
74. The maximum length of a DNA sequence that can be determined using current technology is approximately _______ base pairs.
1. The material that changed R strain pneumococcus into the virulent S strain was originally referred to as the _______.
2. The nitrogenous bases classified as purines are _______ and _______.
3. Watson and Crick used three-dimensional representations of the possible molecular structure of DNA to determine its actual structure. This process is called _______.
4. The nitrogenous bases classified as pyrimidines are _______ and _______.
5. The X-ray crystallographs of the English chemist _______ were essential for the discovery of the structure of the DNA molecule.
6. The basic units of DNA and RNA molecules are the _______.
7. The purines take up (more/less) _______ space in the center of a DNA molecule than the pyrimidines do.
8. Since the DNA molecule is continuous, nucleotide pair after nucleotide pair, their information must lie in the _______ sequence of the nitrogenous bases.
9. Arthur Kornberg showed that DNA could replicate in the test tube if it contained intact DNA for a template, a mixture of the four precursors (the four nucleoside triphosphates), and _______.
10. The experiments of Meselson and Stahl established the _______ of DNA.
11. Meselson experimental system for studying the mode of replication of DNA, researchers analyze information from a life-form from Mars. After the first round of replication, they see two distinct bands in the This finding is consistent with the principle of _______ replication.
12. The region of DNA where replication begins is called the _______.
13. In bacteria, the enzyme that replicates the lagging strand is _______.
14. In prokaryotes, the enzyme that replicates the leading strand is _______.
15. The fragments of RNA and DNA found on the lagging strand of DNA before RNA removal and ligation are called _______.
16. The repetitive sequences at the end of many chromosomes are called _______.
17. An enzyme that is found in 90 percent of human cancers and may be responsible for the continuous division of cancer cells is _______.
18. An enzyme that catalyzes the addition of any lost telomere sequences is _______.
19. The _______ function of DNA polymerase reduces the number of mistakes by the square of the frequency of the error rate.
20. An automated process that makes multiple copies of short regions of DNA in a test tube is called _______.
21. In a sequencing reaction, the shortest sequences are those that end closer to the _______ end than to the _______ end of the synthesized molecule.
22. The technique that sorts DNA fragments by length and detects differences in DNA fragment length is called _______.
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