Bio119 F2006 Midterm I please put your name on each page

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1 Equations/Tables/Information 1. G = -nf E o (F= the Faraday constant = 96 kj/vmol) 2. Reduction Potentials All are given as oxidized/reduced (number of electrons transferred). When written out the reactions look like this: Oxidized + 2 e- reduced Ox/red (e-) Eo (Volts) CO 2 /glucose (6e-) H+/H 2 (2e-) -0.4 NAD+/NADH (2e-) -0.3 Sº/H 2 S (2e-) -0.2 SO 2-4 /HS - (2e-) -0.2 FAD/FADH (2e-) -0.2 Pyruvate/lactate (2e-) -0.1 TMAO/TMA (2e-) +0.1 HAsO 4 2- /HAsO 2-3 (2e-) +0.1 NO - 3 /NO 2 (2e-) SeO 4 /SeO 3 (2e-) +0.5 Fe 3+ /Fe 2+ (1e-) +0.7 Mn 4+ /Mn 2+ (2e-) O 2 /H 2 O (2e-) +0.8 N 2 O/N 2 (2e-) Gº you might need ATP ADP + Pi -32 kj/mol Page 1

2 1 (4 points). (a) Circle the correct letters in the statement: Chemolithotrophs get their energy from A / B substrates that are C / D. A) Reduced B) Oxidized C) Organic D) Inorganic 1(b) Give an example of a specific chemolithotrophic metabolism. 2 (6 points). You are doctor in a health clinic and are going to see a patient that contracted a bacterial infection in her left ear. You prescribe penicillin to treat the infection. One week later you get a call from your patient complaining the infection is still there. Provide a brief explanation for the failed treatment. In your answer include molecular details about the actions of penicillin and resistance mechanisms. 3 (3 points). Circle the INCORRECT choices about Peptidoglycan: A) Peptidoglycan is an enzyme B) It is part of the cell wall C) Penicillin binds peptidoglycan D) Peptidoglycan is sensitive to Beta-lactamases E) NAG and NAM are connected by 1-3 linkages. Page 2

3 4 (3 points). When choosing a gene for making phylogenetic comparisons describe three criteria that should be met before using this gene. 5 (4 points). (a) Which environment would you most likely find fermentative bacteria (choose one or more answers): A) Cow intestine B) Yogurt C) Hot springs D) Deep sea hydrothermal vent 2(b). For one of the choices you would NOT check, explain why you didn t check it. 6 (9 points). A Bio119L student isolated an interesting bacterium that can metabolize selenate (SeO 4 2- ) using H 2 S as an energy source. Cultures of this strain accumulate selenite (SeO 3 2- ) and Sulfur (S 0 ). (a) is reduced to is oxidized to (b) Calculate the G (show calculations) (C) Estimate the number of ATPs that could be generated during this metabolism. Page 3

4 7 (6 points ). Your pet dog Elvis got out last night and consumed a large amount of water from the local stream that was high in nitrate, sulfate, and arsenate. a) In addition to excretion and absorption, what else could happen to these compounds in the anaerobic environment of Elvis s gastro intestinal tract? b) Rank (from high to low) the three compounds based on the energy released during microbial metabolism in Elvis s intestines. c) Will Elvis be okay? 8 (3 points). A famous microbiologist once said, A lot of hoopla is made about microbial diversity. Based on superficial inspection, the bacteria and archaea hardly seem diversified. What is all the hoopla about? Name 3 unique metabolisms that Prokaryotes can perform compared to Eukaryotes. (1 point each) 9 (6 points). Bill, a geomicrobiologists from NASA, thinks he isolated a microbe from a Martian meteorite. Bill determines part of the sequence for the 16S rrna gene. (a) Determine the evolutionary distance between Bill s strain and the two known prokaryotes listed below. (b) What can you concluded about the origins of Bill s new Martian microbe: doubtful, plausible, or inconclusive? Why? Sequence Data Bill s strain: TGGTACGTTT E. coli: TGGCACGGTT Archaea: TCTACGTTAT Page 4

5 10 (3 points). The cytoplasmic membrane could best be described as (choose as many as are correct): A) an impermeable barrier. B) a passive conduit for intracellular transport. C) selectively permeable. D) slightly permeable to water but impermeable to metabolic solutes. 11 (12 points) Combine as many of the physiological designations (listed below) to best classify the types of prokaryotic metabolisms in a-d (your response should end in troph ). Also, choose the mode of respiration. Energy/Carbon Sources: chemo, litho, hetero, photo, auto, Mode of respiration: I. aerobe II. anaerobe III. facultative anaerobe Energy Source Source of carbon External Electron acceptors Type of prokaryote: Mode of respiration a) H 2 S CO 2 Only oxygen b) Lactate Lactate Oxygen, Arsenate c) Light CO 2 Only oxygen d) Lactate, hydrogen Lactate, pyruvate Only sulfate Page 5

6 12 (3 points). Which statement is true? A) Lophotrichous flagella are tufts on the "ends" of bacterial cells; peritrichous flagella are individual flagella on the "ends" of bacterial cells. B) Peritrichous flagella are all over the bacterial cells; lophotrichous flagella are tufts on the "ends" of bacterial cells. C) Polar flagella are individual flagella on the "ends" of bacterial cells; peritrichous flagella are tufts on the "ends" of bacterial cells. D) Polar flagella are all over the bacterial cells; lophotrichous flagella are individual flagella on the "ends" of bacterial cells. Part (b) Based on your answer above, how would the two types of flagellated cells move if their flagella were to turn clockwise? 13 (6 points). The capillary assay was used to determine the chemotactic response of E. coli mutants compared to the wild-type. Three capillaries, A (Asparate), B (Cobalt), and C (water), were tested for each mutant listed in the table. For each of the E. coli strains rank the three capillaries for the highest, low, and lowest (or equal) number of cells that you would expect to observe in each capillary. Strain wildtype: Rank of Capillaries A, B, C A > C > B flagella mutant: pili mutant: Tar mutant: 14 (4 points). Describe two differences between archaeal and bacterial cytoplasmic membranes. Page 6

7 15 (3 points). If an oxidation reaction occurs, a reduction reaction must also occur because A) electrons cannot exist alone in solution. B) that is what redox means. C) half reactions are written that way. D) actually, reduction is not necessary if oxidation occurs. 16 (12 points). The following section contains statements that are either True or False. Mark each statement either True or False and if you answered False, explain why. a. In a redox reaction the change in free energy is proportional to the change in reduction potentials of reduced and oxidized reactions. b. Substrate level phosphorylations can occur in the electron transport chain. c. Proton motive force is generated during anaerobic respiration. e. Assimilative nitrate reduction results in the secretion of large amounts of nitrite. 17 (3 points). The production of which food item involves the use of fermentative bacteria (choose as many as are correct): A) Cheese B) Bread C) Wine D) Milk Page 7

8 18 (6 points). Anthrax was the first disease to fulfill all four of Koch s postulates. The following statements/observations describe some events that occurred during the discovery of Bacillus anthracis as the cause of anthrax. Not all the statements demonstrate Koch s postulates. Place a number (1, 2, 3, or 4) next to the statement/observation that demonstrates the correct Postulate (1, 2, 3, or 4). Dead cows and sheep contained lots of bacteria. The blood of some dead sheep could cause anthrax in mice. Koch observed the same rod shaped cells in the blood of every infected mouse but not in uninfected mice. Small pieces of spleen from only dead infected mice produce pure cultures of B. anthracis by the hanging-drop method of culturing. When the hanging drops of B. anthracis were injected into healthy mice, the mice died the next day. Only B. anthracis was isolated from these dead infected mice using the same hanging-drop method before. If the dead diseased animals were not immediately destroyed, B. anthracis would form spores. This is how the disease could spread in the environment. Death has to occur in order to prove that a pathogen causes disease. 19 (4 points) Fill in the blanks to complete the statements about enterobactin. a) Enterobactin is secreted by prokaryotes to get from the environment. b) Transport of enterobactin through the membrane requires energy from the proton motive force. c) Transport of enterobactin across the cytoplasmic membrane requires the hydrolysis of. d) The uptake of enterobacterin is an example of transport. Page 8