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BioSc221/325 Exam 2 Name ______________________________ Multiple choice. (2 point each) Choose the one best answer to each of the following questions. ____ What is the fate of pyruvate in a microbe that uses respiration? A. B. C. D. E. It is reduced to lactic acid. It is oxidized to lactic acid. It is oxidized in the Krebs cycle. It is reduced in the Krebs cycle. It is catabolized in glycolysis. ____ What happens to ATP synthesis if the electron transport chain is stopped by addition of an inhibitor? A. ATP synthesis would stop due to a buildup of excess protons outside the cell. B. ATP synthesis will speed up due the excess buildup of protons outside the cell. C. ATP synthesis will stop due to the lack of protons outside the cell. D. ATP synthesis will stop due to excess buildup of protons inside the cell. E. None of the above ____ Which of the following is not an end product of fermentation? A. B. C. D. E. lactic acid acetic acid propionic acid pyruvic acid ethanol ____ The conversion of phosphoenolpyruvate (PEP) to pyruvic acid A. B. C. D. releases CO2 involves the conversion of ADP to ATP involves electron transport phosphorylation none of the above ____ Which of the following is the best definition of fermentation? A. B. C. D. The oxidation of a carbohydrate with organic molecules serving as final electron acceptors The reduction of glucose to pyruvate The complete catabolism of glucose to CO2 and H2O The production of ATP from glucose ____ The primary purpose of catabolism is A. B. C. D. E. generation of ADP biosynthesis generation of ATP degradation of organic molecules oxidation of NADH to NAD+ ____ What is the biological function of the reaction: pyruvic acid + NADH 2 -> lactic acid + NAD+. A. B. C. D. E. reduction of NAD+ oxidation of NADH2 oxidation of pyruvic acid reduction of pyruvic acid formation of lactic acid ____ Why do bacteria need to produce ribulose-5-phosphate via the hexose monophosphate shunt? A. B. C. D. to replenish 6-phosphogluconate to produce 2-keto-3-deoxy-6-phosphogluconate (KDPG ) to produce pentose sugars for nucleotide synthesis to fix CO2 ____ What can anoxygenic phototrophs use as an electron source? A. B. C. D. E. water oxygen sulfide nitrate CO2 ____ The photosynthetic bacteria best suited for growth in the lower areas of a pond are the A. B. C. D. E. cyanobacteriu heliobacteria purple sulfur bacteria green sulfur bacteria purple nonsulfur bacteria ____ Which of the following major types of phototrophs carry out oxygenic photosynthesis? A. B. C. D. E. purple bacteria green sulfur bacteria green nonsulfur bacteria Heliobacterium cyanobacteria ____ Carotenoids function in which part of the photosynthetic apparatus? A. B. C. D. Light harvesting center (antenna) Reaction center Electron transport chain None of the above ____ How many molecules of ATP can potentially result from the reaction: pyruvic acid + NADH 2 -> lactic acid + NAD+? A. 0 B. 1 C. 2 D. 3 E. 38 ____ The cyanobacteria can fix gaseous nitrogen in structures termed A. B. C. D. hormogonia akinetes cyanophycin heterocysts ____ Some cyanobacteria, such as Synechococcus do not produce specialized structures to protect their nitrogenase so to avoid harming nitrogenase they A. B. C. D. fixi nitrogen at night live in areas where there is low light intensity consume the oxygen as soon as it is produced form communities that keep out oxygen ____ In microorganisms that can synthesize all their cellular components, there is a central core of metabolic pathways consisting of A. B. C. D. E. glycolysis tricarboxylic acid cycle hexose monophosphate shunt all of the above none of the above ____ The most metabolically versatile of the photosynthetic bacteria is A. B. C. D. green sulfur purple sulfur purple nonsulfur cyanobacteria ____ The major role of the tricarboxylic acid cycle in an autotroph or anaerobe is to provide A. B. C. D. precursor metabolites energy energy and precursors none of the above ____ An anapleurotic reaction is a reaction that A. B. C. D. is used to ferment amino acids produces multiple fermentation products replenishes key intermediates of the TCA cycle fixes carbon dioxide ____ In some cultures cyanobacteria are used as a high protein food source. These generally belong to the genus A. B. C. D. Spirulina Anabaena Rhodococcus Nobody would be foolish enough to eat cyanobacteria ____ A common compound in CO2 fixation and glucose catabolism that is a precursor metabolite (where the two pathways meet) is A. B. C. D. phosphoglyceric acid glyceraldehyde-3-phosphate pyruvic acid phosphoenolpyruvate ____ An organism was isolated that could utilize gaseous nitrogen (N2) as sole source of nitrogen for growth. It would be safe to assume that this isolate is a A. B. C. D. E. bacterium fungus plant virus any of the above ____ An enzyme complex found in both anoxygenic photophosphorylation and electron transport phosphorylation is A. B. C. D. reaction center bc1 complex special pair bacteriopheophytin _____ Based on what you have learned about the elements that control synthesis of the enzymes for tryptophan synthesis, what effect on enzyme activity would you expect under the following conditions: a mutation in the trpR gene, encoding TrpR the tryptophan repressor, such that TrpR can bind DNA without the co-repressor A. B. C. D. constitutive, high-level activity no activity in the absence of tryptophan, high-level activity in the presence of tryptophan high-level activity in the absence of tryptophan, no activity in the presence of tryptophan no activity under any conditions _____ Based on what you have learned about the elements that control synthesis of the enzymes for tryptophan synthesis, what effect on enzyme activity would you expect under the following conditions: a mutation in the trpR gene coding for the tryptophan repressor such that TrpR cannot bind tryptophan A. B. C. D. constitutive, high-level activity no activity in the absence of tryptophan, high-level activity in the presence of tryptophan high-level activity in the absence of tryptophan, no activity in the presence of tryptophan no activity under any conditions _____ A repressible operon is important in regulating _____. A. B. C. D. Amino acid synthesis DNA replication Sugar metabolism ATP synthesis _____ Catabolite repressor protein (CRP) binds to DNA when bound to ____ and ____ expression of catabolic operons such as the lac operon. A. B. C. D. E. Glucose, represses Glucose, activates cAMP, represses cAMP, activates Lactose, represses _____ The site of interaction between RNA polymerase and DNA that initiates transcription is called the ___. A. B. C. D. Pribnow box Shine-Dalgarno sequence Promoter Operator ___ Quorum sensing systems use ___ to determine cell density. A. B. C. D. cell-cell contact autoinducer luminescence phosphotransferase ____ Promoter strength is determined by A. B. C. D. the DNA sequence of the promoter region the number of operators how close the promoter is to the start of transcription the DNA sequence of the ribosome binding site ____ Protein involved in transcriptional termination. A. B. C. D. core enzyme stem loop rho sigma ____ Genes encoding the enzymes required for utilization of maltose as a growth substrate are likely to be controlled by what type of repressor? A. inducible B. repressible C. constitutive ____ In two-component regulatory systems a signal is relayed to the regulator protein by A. B. C. D. phosphorylation adenylation autoinducer a peptide ____ Genes encoding the enzymes required for synthesis of the amino acid tyrosine are likely to be controlled by what type of repressor? A. inducible B. repressible C. constitutive ____ Several genes that are transcribed in the same direction and share the same promoter are called a(n) A. B. C. D. operator operon polylinker polypromoter ____ Small protein that associates with bacterial RNA polymerase to facilitate promoter recognition and is released during transcription. A. B. C. D. alpha beta gamma sigma ____ Genes that are expressed at the same level at all times are said to be A. B. C. D. constitutive inducible repressible activated ____ Most prokaryotic promoters have a two-part consensus sequence that consists of a A. B. C. D. promoter and terminator promoter and operator activator and operator –10 and –35 region Short answer. (variable points) (2) The Fnr protein of E. coli can function as both a repressor and an activator. Describe the likely location of the DNA binding site for Fnr relative to the promoter when it is functioning as an: Activator Repressor (4) In the lac operon expression of the enzyme -galactosidase is under the control of the lac repressor (LacI) which binds at the lac operator (lacO). Complete the table with High if -galactosidase is expressed at high levels under the conditions described or Low if -galactosidase is expressed at low levels under the conditions described. Assume glucose is not present. Mutation lacI- - doesn’t make LacI Lactose present Lactose absent lacIs - LacI can’t bind lactose (1) Bacteriochlorophylls can be found with very diverse absorbance spectra. What advantage does this provide for the phototroph? (1) Anoxygenic photophosphorylation is also called cyclic photophosphorylation. Since the electrons can be recycled, why do these organisms need an electron donor? (4) The cartoon below depicts a standard electron transport chain from NADH/H + to O2. How many coupling sites (locations where protons are translocated) are present in this electron transport chain? Indicate the location of each coupling site with an arrow and an H+ (2) In the TCA cycle, one other hydrogen carrier is used in addition to NADH. Electrons from this molecule (FADH) follow nearly the same pathway to oxygen but only yield 2 ATP. Now that you know how electron transport is coupled to ATP synthesis, predict the reason why only 2 ATP may arise from FADH oxidation. (1) Give one reason why an organism would want to hydrolyze a molecule of ATP to make the ATP synthase enzyme to run “backwards”. (4) Here are several electron carriers found in an electron transport chain and their respective redox potentials. Draw an electron transport chain with the electron carriers in the correct order. Cytochrome c (+300mV), Quinone (+60mV), Ferrodoxin (-200mV), Iron-Sulfur center (-100 mV), Cytochrome b (+100 mV) Electron donor → Electron → acceptor Short Essay Questions. Please answer 3 of the following 4 short essay questions (6 points each - 6 bonus points possible for answering all 4 questions) What are some basic differences and similarities between fermentation and respiration using glucose as the carbon and energy source? In the first section of this class we discussed stromatolites which are fossilized microbial mat communities. The microbial mats consisted of layers of different prokaryotic phototrophs. Based on what you have learned about the properties of the different kinds of phototrophs in this section of the course, explain the basis for this layering phenomenon and the types of organisms you would expect to find in the different layers. It has been assumed for many years that plants account for most of the “fixed” carbon on earth. However, microbes are being discovered in significant quantities in environments such as the open ocean and in subsurface areas and it is now becoming clear that microbes account for most of the “fixed” carbon on earth. Consequently, we have also discovered that microbes have evolved several mechanisms for “fixing” carbon dioxide. Briefly discuss three mechanisms of carbon dioxide fixation found in microbes. Draw a growth curve of E. coli transferred from a stationary phase culture growing in minimal glucose medium to a minimal medium containing a small amount of glucose and lactose. Show optical density vs. time. Describe what is happening at various key points and why?