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FinalExam - BIO 226R Final Exam — Key ’ Dr Earhart...

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Unformatted text preview: BIO 226R Final Exam — Key May 11, 200’? Dr. Earhart There are 16 short answer questions, numbers 1-16. They are worth either 3 or 4 pts; the 4 pt. questions are indicated by (4). There are 21 multiple choice questions and each is worth 2 pts. {numbers Iii-37] NAME UT EID t . 1|What components are common to all viruses? p. 33! Genetic material {RNA or DNA} and a protein shell {capsidl 2. I (4} How do chemoheterotrophs and photoheterctrophs differ with respect to their fueling reactions? p. f? A chemoheterotroph uses organic compounds as both its energy and carbon source. A Photoheterotroph uses 1131;; as its energy source and, like the chetnoheterctroph, uses organic compounds for its source of carbon. 3. 1Wltat is the difference between regulons and modulons'? p. 242 A modulon is a larger, more comprehensive, regulatory grouping. A regulon is a group of independent owns governed by the same regulator, usually a protein repressor or activator. A modulon is a group of independent operons subject to a common regulator, even though they are members of different regulons. 4. What prevents ribosomes from initiating protein synthesis at AUG sequences within open reading frames? p. I52 An authentic start codon is preceded approximately It] nucleotides upstream by a sequence cf4-fi NMPs that is complementary to the 3’ end of the in s RNA of the 3tls ribosomal subunit. l.e., authentic start eodons are preceded by a Shine-Dalgamo sequence to position the Bills on the mR and start formation of the initiation complex. 5. (4) lCiiven: An E. soft It. lysogen {Erot'i [1]). A culture of this strain is irradiated with UV light. What would happen in the next hour or so? Why? p. 343 UV irradiation induces it. The propbage is excised and replicates freely [lytically), leading to lysis of the cell. In approximately an hour the culture would clear because the it had lyscd all the cells. {Uhi serves to activate the coprctease activity of RecA [RECA*} so that the i. repressor cleaves itself, inducing the ptuphage.) ti. {4] In what ways does a bacterial cell in stationary phase differ {tom the same cell in exponential growth? pp. 2553—262 Stationary phase cells are smaller and tougher to break. The phospholipid composition is altered so there is an increase in cardiolipin, at the expense of phosphatidyl glycerol, and many unsaturated fatty acids are converted to cyclopropane Pets. The stationary phase signal factor (0'5 causes changes in transcriptional patterns and the nuclcoid is more condensed. 7. What, if anything, could you surmise about an organism that had no catalase or superoxide dismutase enzymes“? pp. 98-99 The organism would he an obligate [strict] anaerohe as it has no way to protect itself from toxic forms of oxygen [RUB-reactive oxygen species}. (H20: and 02' could net be converted It} 02 and H10.) 8. Some viruses have enzymes included in their virions. What is the usual function of these ' enzymes? pp. 331338 The enzymes are required for replication of the viral genetic material. I.e., host cells have no enzyme capable of making an R copy of R [RNA replicase}. If the viral RNA cannot fimction as mRNA to direct the synthesis of an RNA replicase, the necessary enzyme must be part of the virion. 9. {4) Describe how ATP is generated by transmembrane ion gradients. p. ill] Transrnembrane ion gradients {usually protons but in rare cases sodium ions) use the enzyme Fl Flt synthase to make ATP. The synthase is in the cytoplasmic membrane and passage, e.g., of protons from the outside (hi [H*] to the cytoplasm (low [H+] — where the protons move down a pH and charge gradientrtakes place through the synthase, with concomitant formation of ATP. (Usually respiratory chains or photosynthesis generates this proton motion force [ion gradient].} it]. [4} Is it possible for an organism to be an autotroph and not rely on light for energy? Explain p. 93 Yes. Chernoautotrophs (chemolithotrophs) use chemical, not light energy, to provide energy for the dark reactions of photosynthesis {and are therefore autotrophs]. Chemoautotrophs use inorganic compounds as energy sources. 1 l. [4] Contrast viroids and prions with respect to composition and the hosts in which they cause disease. pp. kill-349 Viroids are small circular molecules of RNA that cause disease in plants. Prions are proteins that cause degeneration of the central nervous system in humans and other animals. 12. {4] What are the usual components of a bacterial sensory or response-regulatory system? For each component, describe its chemical nature, its role in the system and where it is located in the cell. p. 25! Two component regulatory systems consist of a histidine kinase, usually located in the cytoplasmic membrane, and a phosphorylated response regulator, which is cytoplasmic and generally acts as a transcriptional activator. In response to a stimulus, the HK will autophosphorylate and then pass the Pt'ls'2 to the RR, which in its phosphorylated form is active. The HR will often have phosphatase activity to remove P; from BgRR. 13. How do hydrophilic compounds with a molecular mass of son daltons or less enter the gram- negative periplasm? p. 2? The outer membrane contains Erin proteins. which are h‘imeric, and which. in the case of llClmpl-l' and DmpC proteins, are non-specific. They form transmembt'ane channels in the GM. 14. (4} Allosteric interactions modulate the activities of enzymes. Expiain how allostery also plays a role in modulating the amounts of enzymes by controlling gene expression. pp. 2213!} Regulatory (+ or -) proteins are allosteric and the binding of a small molecule (inducer or compressor} determines whether or not they can hind DNA. E.g., Lacl will bind fact? and prevent transcription of the Lac operon. In the presence of inducer (Laciallolac). the inducer binds Lacl, changing its conformation so that it no longer binds DNA. 15. [4} How do the autoinduoer signal molecules ot'gram- negative bacteria differ chemically from those produced by grarn- positive bacteria? pp. Edit-QR? Gram-negative Als are acylated-homoserine lactones and gram-positive Ms are peptides. Gm‘ Ala can move through membrane easily, unlike 1'er+ Ala. lo. [4} Flagella and type IV pili can both be used for bacterial motility but the mechanisms by which they confer movement are quite different. Explain. p. 264 F lagella propel bacteria by rotating like a propeller. The flagellar filaments are rigid, corkaoI'EW-like attuctures. In E. coli, counterclockwise rotation produces smooth swimming. p. 258 Type l‘v’ pili use a grappling hook mechanism. The tip of the pilus has an adhesin so the tip can attach to a surface. The piius, anchored in the cytoplasmic membrane, can disassemble, pulling the bacterium toward the point of adhesion. Type IV pili can be assembled and disassembled rapidly. 1?. The outer and inner membranes of'gram-negative cells a) Both contain lipopolysaccharide b} Both contain respiratory chains c} Are both phospholipid bilayers d} None of the above 13. Winch ot‘ the following statements is true regarding the variations in macromolecular composition of bacteria with growth rate? a) Faster growing cells are relatively richer in DNA b] Faster growing cells are relatively richer in RNA c] Faster growing cells are relatively richer in protein d] All of the above are true [9. 2t]. El. 22. 23. 24. 25. An infectious center a} Can, when plated with a bacterial lawn, give rise to a plaque b} Is a pathogenic bacterium c} is a virus capable of causing disease in animals d) All of the above The conjugative plasmid F a) Is a large circular DNA molecule . b) Can transfer bacterial genes to another cell only if it has first integrated into the bacterial chromosome c) Encodes sex pilus proteins 11} All of the above A crucial difference between fermentation and anaerobic respiration is that a} ATP synthesis via substrate level pbosphorylation occurs only in organisms using fermentation as their fueling process h} Duly anaerobic respiration requires an electron transfer {transport} system c} Only fermentation requires oxygen d) All of the above An example of a mutation that could convert a temperate to a lytic phage would be one that a) Altered a phage structural component so the phage now recognizes new host cell receptors b] Prevented the phage fi'em lysing its host e} Led to synthesis of a defective repressor d} All of the above Methylation of DNA has a role in all of the following DNA activities except a} Repair b} Initiation c) Priming d) Protection In nitrogen assimilation, the key small components are a) Glucose and galactose b) Glutamate and glutamine c] Serine and cysteine d] Lactate and glyceroi 1|Ill-that macromolecule is present in the largest amount in bacterial cells? a) Protein b) RNA c) murein d) DNA 26. 2?. 28. 29. 3E). 31. Phosphotranf'erase transport systems :1) Modify the solute during the course of uptake b) Are used mainly for amino acid transport o} Are found in all three domains of life d} None ofthc above Given: an organism containing peptidoglycan. You knew a} This is a pathogen b} The organism contains lipopolysaccharide c} This organism belongs to the domain Bacteria d} None of the above You examine the DNA content of newborn cells in a culture of growing bacteria and find each newborn cell has more than one genome’s worth of'DNA. A possible explanation for this is a} The cells are trom a rapidly-growing culture 1}) The cells are mutated in their minC genes c] The oells have too much DNA polymerase Pol 1H d) None of the above 1|What would be a phenotype of E. colt growing in the absence ofTrp if its rrpL_region were deleted? a} It would be unable to grow b} It would make less Trp mRNn. than usual c} Its Trp tnRNA would be unstable d} It would make more Trp mRNA than its wild-type parent The Embdcn—Meyerhof—Pamas (glycolytic) pathway a} Does not require oxygen b} Yields two molecules ofpyruvate c] Producos many precursor metabolites d] All of the above The See system a) ls responsible for secretion of proteins in gram- positive bacteria h) Recognizes substrate proteins through their N terminal signal sequence c] ls responsible for export of most periplasmic and outer membrane proteins ofgram- negative bacteria d] All ot the above 32. 33. 34. 35. 36. 3?. A transducing phage a) Must be able to lysogenize b) Must have a very broad host range c] Must not completely degrade the DNA of its bacterial host during lytie growth :1) Must be able to adjust the size of its head Given: Two E. coli strains. Strain A cannot synthesize the Lacl protein and Strain B has its fact} mutated such that it is unrecognizable by repressor. When placed in a relatively poor growth medium in which glycerol is its only source of carbon dc energy, a} Neither strain would produce B-galactosidase b) Both strains would produce ll-galactosidase c} Strain A would produce B~gaiactosidasc and strain B would not d} None of the above Translators for protein synthesis consist of a} The a, [3 dz [3’ subunits of RNA polymerase b} The 23 S ribosomal RNA c} Amino acyl tRNA synthetases and tlw'tNA d} None of the above An integrase enzyme a} Can convert single-stranded RNA into single-stranded DNA b) Can convert single-stranded RNA into double-stranded DNA c} Can degrade small regulatory RNAs d} None of the above Rho-independent {simple} transcription termination dilTers from Rho-dependent termination in that a} Simple terroioation is used only for RNAs with short half- lives b} Simple termination requires ppGpp c} Simple termination occurs only in gram- positive bacteria d} Simple termination depends on RNA secondary structure Given a test tube of motileE. coii. Rapid addition ofrepeiient would have what efi'ect? a} The bacteria would all swim for a prolonged period b} The bacteria would aggregate length-wise with respect to one another c} The bacteria would tumble continuously for a prolonged period d) The bacteria would precipitate out and collect on the bottom of the test tube ...
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