bio practice final answers

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Unformatted text preview: ©Prep101 Biology 112 Practice Final Exam 1) Natural selection: 1. acts on the genotype and not the phenotype 2. is determined by the effects of the environment on the genotype of the organism 3. acts upon the phenotype but is a consequence of changes in genotype 4. requires that an organism reproduces and produces identical offspring Which statements are true: a) 1 + 2 b) 2 only c) 2+3 d) 3 only Answer: C. Natural selection is the selection of phenotypes in a particular environment that provides a selective advantage. Phenotype is dictated by the genotype and the environment therefore C. is correct. 2) Some changes in genotype have no effect on phenotype. Which if the following is true: a) A mutation in the non-coding region of a gene will have very little effect on the phenotype b) A frame shift mutation anywhere within a coding region for a gene will cause the same phenotype. c) A change in genotype could have a huge effect on phenotype or none at all d) A point mutation upstream of the coding sequence will have no effect on the phenotype e) All of the above. Answer: C. This is a common question topic. With most mutations it is impossible to predict the phenotypic consequence of the change in genotype. 3) All electron transport chains require a) b) c) d) e) NAD+ or NADP+ to be the terminal electron acceptors. Electron carriers to be arranged from low to high electronegativity. ATP hydrolysis to supply the energy for electron flow. Electrons to enter the chain associated with stable compounds. Both A and C are correct. Page 1 of 8 ©Prep101 Answer: B. All ETCs are a set of increasing strength of electron acceptors that shuttle electrons to harness energy in discrete steps. Higher electronegative atoms are stronger electron acceptors therefore B is correct. 4) You have designed an experiment in which you feed glucose containing radioactive carbon molecules to cells growing rapidly in the presence of oxygen. Over time, you would find the radioactivity in a) b) c) d) e) ATP NADH + H` lactic acid H2O CO2 Answer: E. If an organism can use glucose as its energy source it is a heterotroph and in the presence of oxygen it normally undergoes cellular respiration where the complete oxidation of glucose causes the release of all carbons as CO2. 5) Consider the following statements: 1. ATP can be generated through the ETC by utilizing the energy contained in the [H+] gradient to drive ATP synthase 2. Nutrient oxidizers tolerate oxygen 3. Waste products of lithotrophs include ethanol, acetic acid, or lactic acid 4. Na3PO4 could be used as a source of bioelement, phosphorus. a) b) c) d) e) None of the statements are valid Only one statement is valid. Two statements are valid. Three statements are valid. All statements are valid. Answer: D. Statement #1 describes chemiosmosis, Statement 2 is a general statement and can be true. Statement #3 is false –lithotrophs do not ferment and ethanol, acetic acid and lactic acid are products of fermentation. Statement #4 is true. 6) Design a theoretical medium that would specifically inhibit the growth of all lithoautotrophs except methanogens. (Hint – what is the difference between methanogens and other lithoautotrophs?) Answer: CHOPSN sources. But the only difference between methanogens and the other anaerobic lithoautotrophs (eg sulfur reducers) is that methanogens use a different mechanism to fix carbon than other lithoautotrophs – they do NOT have Rubisco. Page 2 of 8 ©Prep101 Therefore in the medium would be a Rubisco inhibitor 7) Which of the following are considered both waste products and nutrients in both heterotrophs and lithotrophs, depending on the cellular reaction? a) b) c) d) NO3 NADH S° Glucose Answer: A. Both NADH and glucose are never considered waste products as they contain too much energy to waste. Elemental sulfur is completely reduced therefore cannot act as a nutrient whereas NO3 can act both as a nutrient (as a TEA) and as a waste for nitrifying bacteria. 8) For transcription to occur in the lactose operon, an inducer must be present so that a) b) c) d) the repressor can bind to the operator the repressor does not bind to the operator the inducer can bind to the operator the inducer does not bind to the operator Answer: B. The repressor, from the lacI gene, is responsible for binding the operator region of DNA at the promoter to inhibit transcription in the absence of lactose. Once the inducer (lactose) is present it binds the repressor causing the repressor to dissociate off the DNA and allowing transcription. 9) Which of the following is false for endospores? a) They have no detectable metabolic rate and are thus the least starvationresistant biological structures b) They are very resistant to the damaging effects of UV radiation c) Their DNA is thought to be complexed with special proteins which protect it from UV radiation d) They are the most heat resistant biological structures known e) They can survive boiling for extended periods of time Answer: A. Endospores have a very low metabolic rate but it is not undetectable. They are highly resistant structures that are resistant to irradiation, heat, dessication and low nutrient availability. Page 3 of 8 ©Prep101 10) Bacteria respond to a positive chemotaxis through 1. Temporal mechanism 2. Spatial mechanism 3. Sensing proteins 4. Tumbling 5. Twiddling 6. Running a) b) c) d) e) 1, 2, 3, 4, 5, 6 1, 3, 4, 5, 6 1, 3, 4, 5 1, 3, 6 2 Answer: B. Bacteria can only respond to a temporal mechanism to detect differences in chemical concentrations. In the response to a positive stimulus the bacteria swims towards the attractant by running in that direction and it senses the attractant by special receptors. 11) With respect to its ability to utilize lactose as a carbon source, what is the phenotype of a strain of E. coli lacking the repressor? Explain the cause of this phenotype? Answer: This strain can utilize lactose and, furthermore, the lactose operon is costitutively expressed because i- indicates that no functional repressor can be made. Thus, the operon is expressed even when there is no lactose in the medium. 12. Heterocysts are specialized cells that carry out _____ in species of _______. a) b) c) d) e) nitrification/algae nitrogen fixation/fungi denitrification/cyanobacteria nitrogen fixation/cyanobacteria all of the above Answer: D. Heterocysts are produced in species of cyanobacteria to act as an anaerobic nitrogen fixation cell among the population of photosynthetic aerobes. Page 4 of 8 ©Prep101 13. Heterotrophs are characterized by all of the following except: a) b) c) d) Heterotrophs only obtain carbon from organic nutrients Heterotrophs do not require ATPase activity Heterotrophs only use organic nutrients Fermentation can produce ethanol or lactic acid. Answer: C. Heterotrophs obtain energy from organic nutrients but are not completely restricted to organic nutrients because there are photoheterotrophs that obtain energy from light and yet use organic carbon as a carbon source. 14. Predict the phenotypic effects of a mutation in the electron transport chain that completely abolished a components electron carrying capacity. a) A proton gradient would be established, but the production of ATP would be inhibited b) Both the establishment of a proton gradient and electron movement through the ETC would not happen. c) Electrons would be unable to channel through the ETC, and therefore no oxidative phosphorylation would occur d) ATPase activity would still occur but the electron transport chain would not pass on the electrons to the TEA. e) The TEA would be reduced but a proton pumping event would be inhibited. Answer: C. If a mutation in the ETC prevents electron passage then a block would occur and no ATP formation would occur using ATP synthase and the proton gradient produced by the ETC. ATP is produced by the ETC by oxidative phosphorylation. 15. If a mutation occurs in a gene coding for a ribosomal protein causing a change of one amino acid in the mRNA binding site from a Gly to a Lys what would be the result? Explain. Answer: • What is the difference between Gly and Lys (therein lies the answer…) • Gly is non-polar • Lys is polar • Therefore protein folding will likely be affected • This amino acid was in the mRNA-binding domain • The mutant protein will likely not be able to bind mRNA Page 5 of 8 ©Prep101 16. Despite the fact that cows ingest air as they graze, the rumen is an anaerobic environment. This is partly due to the metabolism of a) b) c) d) obligate aerobes facultative anaerobes microaerophiles obligate anaerobes Answer: B. Facultative anaerobes utilize the available oxygen before it can become toxic to the methanogens and other anaerobic microbes that live in the rumen. 17. Plasmids are directly transferred between bacterial cells by: a) b) c) d) e) transduction conjugation transformation sigma factors reverse transcription Answer B. Conjugation is the transfer of plasmids directly between bacterial cells, for example the transfer of the F plasmid. Transduction requires a bacteriophage intermediate and transformation is the uptake of naked DNA. Match the genetic exchange system given below with the descriptions in the next five questions: A. Conjugation B. Transduction C Transformation 18. Involves cell free or naked DNA: __C__ 19. Requires a fertility plasmid: __A__. 20. Most common way antibiotic resistance genes are spread: __A__. 21. Mediated by bacteriophage: __B__. Page 6 of 8 ©Prep101 22. In the metabolism of a heterotrophic bacterium: If a nutrient donates electrons to a TEA, then it is being used as an __________ for the purpose of synthesizing __________ . If a nutrient donates electrons to NADP+, then it is being used as an __________ for the purpose of synthesizing __________. a) b) c) d) e) electron source, ATP, energy source, NADPH energy source, NADPH, electron source, ATP electron source, NADPH, energy source, ATP energy source, ATP, electron source, NADPH Mark (e) if the answer is NONE of the above. Answer: D. Heterotrophs that use an electron donated to a TEA to produce ATP is using this nutrient as an energy source. If the electron is transferred to NADP+, for instance in harnessing of light energy the nutrient is being used as an electron source to produce NADPH. 23. Choose the statement that is false regarding the following cellular reaction: 8H+ + 8e- + N2 a) b) c) d) e) 2NH3 + H2 Is energetically demanding Involves nitrogen fixation by nitrogenase Occurs in symbiotic bacteria Requires anaerobic environment All of the above Answer: E. Nitrogen fixation is energetically demanding, requires nitrogenase activity which requires an anaerobic environment and occurs in symbiotic bacteria in root nodules. Therefore all are correct. 24. Which one of the following is a product of both noncyclic and cyclic photophosphorylation? a) b) c) d) e) NADPH ATP Carbohydrate H2O O2 Page 7 of 8 ©Prep101 Answer: B. Noncyclic and cyclic phosphorylation both produce ATP but cyclic does not produce NADPH. This is to account for the more ATP being used than NADPH. 25. The operator region of an associated operon a) b) c) d) codes for the synthesis of a repressor is a nucleotide sequence of DNA that binds an active regulatory protein binds RNA polymerase at the beginning of transcription of an operon is a nucleotide sequence of an RNA molecule which is not translated into protein e) none of the above Answer: B. The operator is a DNA sequence near the promoter to which activators and repressors can bind to regulate transcription of an operon. 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This note was uploaded on 01/06/2011 for the course BIO 112 taught by Professor Taylor during the Fall '09 term at The University of British Columbia.

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