Test Bank Cell and Molecular Biology Concepts and Experiments 7th Edition Karp

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1 Test Bank Cell and Molecular Biology Concepts and Experiments 7th Edition Karp Completed downloadable package TEST BANK for Cell and Molecular Biology Concepts and Experiments 7th Edition by Gerald Karp nts-7th-edition-test-bank-karp/ Package Title: Test Bank Course Title: Karp6e Chapter Number: 3 Question Type: Multiple Choice 1) The energy stored in ATP is converted to mechanical energy that moves organelles around within the cell. This is an example of. a) being exothermic b) being endothermic c) energy transduction d) polymerization e) catheterization c 2) Entropy is associated with the movement of particles of matter, which because they are cannot accomplish a directed work process. a) rapid, directed b) random, random c) rapid, random d) slow, rapid e) random, slow b

2 3) Enthalpy is. a) the energy available to do work b) the total energy content of a system c) named after J. Willard Gibbs d) the energy available to do work and the total energy content of a system e) All of these are correct. b 4) Given the equation G = H - T S, which set of conditions would result in a reaction that is unambiguously nonspontaneous? a) entropy decreases and the reaction is endothermic b) entropy increases and the reaction is exothermic c) entropy stays the same and there is no change in enthalpy d) entropy decreases and the reaction is exothermic e) entropy increases and the reaction is endothermic a Difficulty: Hard 5) Which reaction below might be a suitable coupled reaction for the reaction A + B < > C + D ( G = -8.7 kcal/mole)? a) E + F < > G + H ( G = -5.4 kcal/mole) b) B + F < > G + H ( G = -5.4 kcal/mole) c) C + F < > G + H ( G = +8.3 kcal/mole)

3 d) C + F < > G + H ( G = +9.7 kcal/mole) e) A + F < > G + H ( G = kcal/mole) c Difficulty: Hard 6) What kind of organism reaches equilibrium? a) one that is actively metabolizing b) one with a low metabolic rate c) a dead organism d) a eukaryote e) a prokaryote c 7) Which property below is not a characteristic of enzymes? a) They are required only in large amounts. b) They can be altered reversibly during a reaction. c) They do not alter the G of a reaction. d) They are used over and over again. e) They do not determine whether a reaction is exergonic or endergonic. a 8) Enzymes work by. a) raising the activation energy of a reaction and thus speeding up the reaction.

4 b) lowering the activation energy of a reaction and thus speeding up the reaction. c) raising the G of a reaction and thus speeding up the reaction. d) lowering the G of a reaction and thus speeding up the reaction. e) changing the free energy of the products and speeding up the reaction. b 9) What kind of interaction is not involved in the binding of a substrate to a normally functioning enzyme? a) H bonds b) a transient covalent bond c) ionic bonds d) a permanent covalent bond e) hydrophobic interactions d 10) The presently accepted model of enzyme action was proposed by Daniel Koshland in the 1960s and suggested that the enzyme was a flexible structure with an active site roughly complementary to the substrate that binds it. After its initial interaction with the substrate, the enzyme alters its shape and thus improves the fit of the substrate in the active site) What is the name of this model? a) The Induced Fit model b) The Flexible Sponge model c) The Lock and Key model d) The Koshland model e) The Flexible Fit model a

5 11) Doubling the concentration of enzyme will the Vmax and the KM. a) double, not alter b) not alter, double c) double, double d) not change, not alter e) halve, halve a 12) What kind of inhibitor binds very tightly to an enzyme often forming a covalent bond with an amino acid in the active site? a) irreversible b) reversible c) uncompetitive d) reversible and uncompetitive e) None of these are correct. a 13) The effect of a competitive inhibitor can be reversed by. a) increasing inhibitor concentration b) increasing substrate concentration c) heating the reaction mixture d) changing the ph e) massaging the enzyme

6 b 14) What is the effect of a competitive inhibitor on an enzyme-mediated reaction? a) Vmax stays the same, KM decreases b) Vmax decreases, KM is unchanged c) Vmax increases, KM is unchanged d) Vmax stays the same, KM is unchanged e) Vmax stays the same, KM increases e 15) Proteins are dynamic molecules that are capable of motion that can have important functional relevance. The existence of this type of motion has suggested that enzymes are capable - even in the absence of substrate - of many of the same movements that can be detected during their catalytic cycle. a) extrinsic b) intrinsic c) instant d) built-in e) intrinsic and built-in e 16) Metabolic pathways that make available raw materials from which other molecules can be synthesized and that provide chemical energy required for many cell activities are known as.

7 a) anabolism b) catabolism c) manabolism d) allosterism e) anabolism and catabolism b Learning Objective: LO 3.3 Discuss the main differences between catabolic and anabolic pathways, explaining intermediate steps in biochemical reactions. Section Reference: Section 3.3 Metabolism 17) A reaction involving the gain of one or more electrons is a(n) reaction. a) oxidation b) reduction c) inclusion d) elimination e) None of these are correct. b Learning Objective: LO 3.3 Discuss the main differences between catabolic and anabolic pathways, explaining intermediate steps in biochemical reactions. Section Reference: Section 3.3 Metabolism 18) Glycolysis occurs in the ; the Krebs (TCA) cycle occurs in the of eukaryotes and the of prokaryotes. a) cytoplasm, cytoplasm, cytoplasm b) mitochondria, cytoplasm, mitochondria c) cytoplasm, mitochondria, cytoplasm d) cytoplasm, photosynthesis, cytoplasm e) cytoplasm, mitochondria, mitochondria c Learning Objective: LO 3.3 Discuss the main differences between catabolic and anabolic pathways, explaining intermediate steps in biochemical reactions. Section Reference: Section 3.3 Metabolism

8 19) What kind of enzyme adds phosphate groups to enzymes for the purpose of activating or deactivating them? a) phosphatases b) protein kinases c) flippases d) glycosyltransferases e) carboxypeptidase b Learning Objective: LO 3.3 Discuss the main differences between catabolic and anabolic pathways, explaining intermediate steps in biochemical reactions. Section Reference: Section 3.3 Metabolism Question Type: Essay 20) You are observing a reaction and discover that the reaction vessel is warm to the touch. The reaction also results in an increase in entropy. Is the reaction spontaneous? How do you know? Solution: The reaction is exothermic (- H) as demonstrated by the warm reaction vessel and entropy is increased ( S). When these values are plugged into the equation G = H - T S, the only possible result is that G is negative. The reaction has a negative G and is, therefore, spontaneous. 21) If a reaction vessel is cold to the touch and the reaction results in an increase in order in the reaction vessel, is the reaction spontaneous or nonspontaneous? Explain your answer.

9 Solution: The reaction is nonspontaneous. The H is positive and the S negative. When these values are plugged into the equation, G = H - T S, the result is a positive G and, therefore, a nonspontaneous reaction. 22) Do the equations below represent coupled reactions? If not, why not? A + B <-> C + D ( G = -5.4 kcal/mole) E + F <-> G + H ( G = +4.4 kcal/mole) The equations above do not represent coupled reactions because there is no common intermediate. Difficulty: Hard 23) Do the equations below represent coupled reactions? If not, why not? A + B <-> C + D ( G = +5.4 kcal/mole) D + F <-> G + H ( G = -4.4 kcal/mole) Difficulty: Hard Solution: The equations above do not represent coupled reactions because the overall G is not negative. 24) In the reaction A + B < > C + D, how might the reaction take place in the cell if the G is very positive? How might the reaction occur if the G is slightly positive? Difficulty: Hard Solution: If G is very positive, the reaction would probably take place by coupling it to a reaction with a larger - G so that when the G values are added up the sum is negative. If the reaction is slightly positive, it may be coupled as well, although it may also be driven forward by

10 increasing the amounts of the reactants and/or decreasing the amounts of products. The Law of Mass Action would be likely to allow the reaction to run under these conditions. 25) You are observing an enzyme driven reaction. To the reaction mixture you add a chemical X which inhibits the reaction. If you add more substrate, the reaction rate approaches the Vmax of the uninhibited reaction. Furthermore, the structure of X is similar to the natural substrate. What kind of inhibitor is X? Solution: X is a competitive inhibitor. First, competitive inhibitors resemble the substrates of the reactions they inhibit. Second, their effects can be reversed by increasing substrate concentration, since both the substrate and the competitive inhibitor are capable of binding to the enzyme active site. As the amount of substrate increases relative to the competitive inhibitor, the active site is more likely to pick up substrate and thus reaction rate increases and the inhibition is reversed. 26) If ATP is present in relatively high amounts, what is likely to happen to the rate of glycolytic activity in that cell? Solution: The glycolytic pathway will probably slow down. ATP will act like a noncompetitive inhibitor and will inhibit one of the early reactions in the glycolytic pathway. 27) An enzyme has a KM of 20 µm and a Vmax of 50 mmoles of product/minute/µg of enzyme. After exposure to an inhibitor and analysis on a Lineweaver - Burk plot the following values are obtained: -1/ KM = liters/µmole and 1/ Vmax = 0.04 (mmoles of product/minute/µg of enzyme)-1. What kind of inhibitor was used in the experiment?

11 Solution: Since the KM has remained the same and the Vmax has decreased, the inhibitor was noncompetitive. 28) Why are alcoholic beverages often made in airtight containers? Learning Objective: LO 3.3 Discuss the main differences between catabolic and anabolic pathways, explaining intermediate steps in biochemical reactions. Section Reference: Section 3.3 Metabolism Solution: The alcohol in these beverages is produced by fermentation, which only occurs in the absence of oxygen. 29) Below is a segment of a cell's collection of biochemical pathways. M is a product of one series of these reactions. It is also a regulatory molecule. Look at the pathway below and indicate the position(s) at which M is most likely to act as a feedback inhibitor when its concentration gets too high. R A B C D I 3 J 4 K Q P O N M L 5 7 Solution: M will be most likely to act as a feedback inhibitor at position 1, 2 or maybe 3. Usually, a feedback inhibitor will work on an enzyme near the beginning of the pathway that

12 leads to its production. Therefore, positions 1 and 2 are the most likely with 1 being slightly favored. 30) You are studying metabolic pathways and discover that two pathways intersect so that the enzyme basinase participates in both of the intersecting pathways, in one case using substrate K and in the other using substrate M. When presented with substrate K in amounts significantly larger than M, basinase converts K to L which leads eventually to the production of the end product R. The activity of the second pathway is depressed simultaneously. In the presence of large amounts of substrate M and lower amounts of substrate K, the second pathway is activated and culminates in the production of that pathway's end product Y. The activity of the first pathway is depressed simultaneously. What are the alternative substrates K and M acting like? Solution: K and M are acting like competitive inhibitors. If one is present in excess, the pathway involving the other is inhibited. 31) 4 ATPs per glucose molecule are made during glycolysis. Why then is there a net production of only 2 ATPs for each glucose molecule in the pathway? Learning Objective: LO 3.3 Discuss the main differences between catabolic and anabolic pathways, explaining intermediate steps in biochemical reactions. Section Reference: Section 3.3 Metabolism Solution: Two ATPs are used up early in glycolysis before the 4 ATPs are produced. Consequently, there is a net gain of only 2 ATPs per glucose. 32) Why has the pharmaceutical industry drastically cut resources devoted to the development of new antibiotics?

13 Solution: The decrease in the pharmaceutical industry's resources devoted to the development of new antibiotics is generally attributed to three factors. First, there is a lack of financial incentives since antibiotics are taken for only a short period of time, as opposed to drugs prescribed for chronic conditions (diabetes, depression). Second, new antibiotics run the risk of having a relatively short lifetime in the marketplace as bacteria become resistant to each successive product. Last, the most effective antibiotics are being held back from widespread use and being kept instead as weapons of last resort when other drugs have failed. 33) A number of antibiotics attack prokaryotic protein synthesis, but not eukaryotic protein synthesis. Name two common antibiotics that work this way. What is their site of action and why don't they affect eukaryotic protein synthesis? Solution: The antibiotics are streptomycin and the tetracyclines. They act by binding to prokaryotic ribosomes. Eukaryotic ribosomes are sufficiently different from those in prokaryotes to prevent binding of these substances. Thus, eukaryotic protein synthesis is unaffected. 34) Penicillin is an irreversible inhibitor of the transpeptidases, enzymes that cross-link components of the bacterial cell wall. The cell wall is thus fragile and the bacteria die. Penicillin and its derivatives are structural analogs of the natural substrates of these enzymes. Why doesn't penicillin normally kill humans, unless a severe allergic reaction (anaphylaxis) develops? How does penicillin inhibit transpeptidase? Solution: Humans don't have cell walls and transpeptidases. Thus, penicillin cannot inhibit an enzyme that humans do not possess and it will not normally harm humans. Since penicillin occupies the transpeptidase active site, it acts somewhat like a competitive inhibitor, but since it binds irreversibly, it is not truly competitive. 35) If an antibiotic were found to bind to a site on an essential bacterial enzyme other than the active site, what would its most likely mode of action be?

14 Solution: It would probably be a noncompetitive inhibitor of the affected enzyme. 36) You isolate the enzyme that synthesizes folic acid in bacteria and conduct some enzyme kinetics experiments. You find, not surprisingly, that sulfa drugs inhibit the enzyme's activity. What happens to the Vmax and KM of this enzyme when it is treated with sulfa drugs? Why do sulfa drugs have no effect on human metabolism? Solution: Since the sulfa drugs are competitive inhibitors, the Vmax should stay the same and the KM should increase. Sulfa drugs work by acting as a competitive inhibitor of an enzyme that converts p-aminobenzoic acid (PABA) to the essential coenzyme folic acid. Since humans lack a folic-acid synthesizing enzyme, they must obtain this essential coenzyme in their diet and, consequently, sulfa drugs have no effect on human metabolism. 37) What is unusual about the mechanism by which vancomycin inhibits transpeptidation of the bacterial cell wall? Why is it more difficult for bacteria to develop resistance to vancomycin than to other antibiotics? Solution: Vancomycin binds to the peptide substrate of the transpeptidase, rather than to the enzyme itself. Normally, the transpeptidase substrate terminates in a D-alanine D-alanine dipeptide. To become resistant to vancomycin, a bacterial cell must synthesize an alternate terminus that does not bind the drug. This is a roundabout process that requires the acquisition of several new enzymatic activities. Consequently, vancomycin is the antibiotic to which bacteria have been least able to develop resistance and thus is usually given as a last resort when other antibiotics have failed.

15 38) Where is S. aureus usually found in humans? What kind of hospitalized patients develop life-threatening S. aureus infections? Distressingly, instead of just showing up in hospitals, methicillin-resistant S. aureus (MRSA) is showing up in other places. What are some examples? Solution: The skin and nasal passages. Those patients who have open wounds or invasive tubes. It has appeared in community settings, like high school gyms and children's daycare centers. 39) What is the reason for treating a patient simultaneously with two antibiotics against the same bacterium? Solution: The hope is that while a bacterium may have the gene for resistance to one antibiotic, it will not have a gene conferring resistance to the second antibiotic) Also, in the case of penicillin, treatment with penicillin and an agent that inhibits -lactamase may protect penicillin against -lactamase and allow it to work. 40) The development of bacterial resistance to antibiotics is an example of what engine of evolution? Solution: Natural selection. 41) Which antibiotic inhibits the enzyme DNA gyrase, which is required for bacterial DNA replication?

16 Solution: Quinolones 42) Penicillin fits into the active site of transpeptidases and thus acts as what kind of inhibitor? How is the effect of such an inhibitor usually able to be reversed? Why would this approach not work with penicillin? Solution: Penicillin acts as a competitive inhibitor since it occupies the active site. Such inhibition is usually reversible by increasing substrate concentration, which would tend to displace the inhibitor from the active site. An increase in substrate concentration does not reverse penicillin's effect because penicillin forges a covalent bond between itself and the enzyme active site, thus occupying the active site permanently and irreversibly inactivating the enzyme. 43) What are some ways that antibiotic resistance genes can be passed from bacterium to bacterium? Solution: DNA can pass from bacterium to bacterium through conjugation in which bacteria pass DNA through tubelike connections joining two of them together. Bacteria may also exchange genes by the process of transduction in which a virus carries bacterial DNA from one bacterium to another. DNA may also be passed by transformation in which a bacterium can pick up naked DNA from its surrounding medium. 44) How does the AIDS virus manage to avoid the effects of drugs that attack its enzymes so effectively?

17 Solution: The replicating enzyme of HIV is reverse transcriptase. This enzyme has a much higher error rate than DNA polymerase (~1 mistake for every 10,000 bases duplicated) and makes a large number of mistakes leading to a higher mutation rate. When combined with the high rate of virus production (>108 virus particles produced in a person per day), the likelihood of producing drug-resistant variants in a single infected individual is relatively high. 45) Many bacteria have acquired resistance to penicillin by picking up the gene for -lactamase. However, some have developed resistance without acquiring this gene. How do these bacteria escape the fatal effects of penicillin? Solution: Some are resistant because they possess modifications in their cell walls that block the entry of the antibiotic. Others are resistant because they are able to selectively export the antibiotic once it has entered the cell. Still others are resistant because they possess modified transpeptidases that fail to bind the antibiotic as a result of mutations in the gene that encodes the enzyme. 46) What strategies are employed to combat the ability of the AIDS (HIV) virus to develop drug-resistant variants? Solution: One strategy employed is having patients take several drugs at once (cocktails), each of which is targeted at different viral enzymes. This strategy greatly reduces the likelihood that a variant will emerge that is resistant to all of the drugs. Second, drugs have been designed that interact with the most highly conserved portions of each targeted enzyme, those portions within which mutations are most likely to produce a defective enzyme.

18 47) There have been two new classes of antibiotics developed and approved since One of these antibiotics acts specifically on bacterial ribosomes. What is it? Another new group of antibiotics is the cyclic lipopeptides. What is a representative of this group and how does this group of antibiotics work? Solution: The antibiotic linezolid (brand name Zyvox) acts specifically on bacterial ribosomes and interferes with protein synthesis; it was introduced in A representative cyclic lipopeptide is daptomycin (brand name Cubicin). They disrupt bacterial membrane function. 48) Certain bacteria have an adaptation that allows them to render penicillin harmless; they have adapted due to their possession of an enzyme called penicillinase. How does it render them immune to the effects of penicillin? Solution: Another name for penicillinase is -lactamase. This enzyme can open the -lactam ring. Penicillin is a -lactam because it contains the four-membered -lactam ring. Thus, penicillinase breaks the ring and renders penicillin harmless to the bacterium. 49) Why was methicillin developed? Solution: Methicillin is a penicillin derivative that is more resistant to hydrolysis by penicillinase) Unfortunately, natural selection leads rapidly to the evolution of bacteria whose -lactamase can split the new forms of the antibiotic. 50) How are new compounds typically screened for their effectiveness as antibiotics?

19 Solution: A compound is tested for its ability to kill bacterial cells that are growing in a culture dish or a laboratory animal. Alternatively, it is tested for its ability to bind and inhibit a particular target protein that has been purified from bacterial cells. Completed download at: cell and molecular biology karp test bank cell and molecular biology karp 7th edition test bank cell and molecular biology concepts and experiments 7th edition pdf cell and molecular biology karp 7th edition test bank free karp cell and molecular biology pdf cell and molecular biology karp 8th edition pdf cell and molecular biology by gerald karp 7th edition pdf free download karp cell and molecular biology 8th edition