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MIT 7 014 - Quiz III

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7.014 Quiz III Handout• Quiz III: Wednesday, April 14 12:05 - 12:55 Walker Gym**This will be a closed book exam**• Quiz Review Session: Tuesday, April 137:00 - 9:00 pmroom 54-100• Open Tutoring Session: Monday, April 124:00 - 6:00 pmroom 66-1562Question 1Shown below is the portion of the diagram from page 10 that shows the electron transportpathway. In this pathway, electrons are transferred from NADH to O2; the energy of thisreaction is coupled to pumping of H+. NADH + H+(FADH2)NAD+(FAD)2 e-O2H2O2 e- H+ (in space A) H+ (in space B)electron transportproton pumping2 e-drug Xdrug Y2 e-Under normal circumstances, cells carrying out respiration:• consume O2• produce CO2• produce 36 ATP per glucose consumedTwo drugs, drug X and drug Y, can pick up electrons from particular intermediates in thispathway. This is shown above.a) You treat cells carrying out respiration with a saturating dose of drug X, so that all theelectrons which would normally continue along the pathway are captured by drug X.Under these conditions:• Will the cells continue to consume O2?• Will the cells continue to produce CO2?• Will the rate of ATP synthesis increase or decrease or stay the same?Explain your reasoning.b) You treat cells carrying out respiration with a saturating dose of drug Y, so that all theelectrons which would normally continue along the pathway are captured by drug Y.Under these conditions:• Will the cells continue to consume O2?• Will the cells continue to produce CO2?• Will the rate of ATP synthesis increase or decrease or stay the same?Explain your reasoning.3Question 2You have just won the lottery and you and 10 friends decide to sail around the world inyour new yacht. Unfortunately, due to stormy seas in the Pacific, you find yourselvesshipwrecked on a remote island near Micronesia. Several other species of life inhabit thisisland and its immediate surroundings: in the waters there are blue-green algae(cyanobacteria), and fish; and on the island there are trees and edible plants, plant-eatingboars, lions, and now you.a) Indicate which of the above species (on land and water) are autotrophs and which areheterotrophs. What is the source of energy for each group?AutotrophsSpecies Energy HeterotrophsSpecies Energyb) The following diagram represents the metabolism of an organism mentioned above. H+ gradientATPADP + Pie–NADPH + H+NADP+lighte–i) Fill in the boxes using the following starting materials for carbon metabolism(Note that the metabolism you propose may produce compounds not on the list, butit may only consume compounds on the list).Fe3+H2O Mn4+glucose CO2H+ii) What type of metabolism does this represent?iii) Explain why this organism is either autotrophic or heterotrophic.4Question 2, continuedc) Complete the table below for oxygenic photosynthesis and chemosynthesis. Include theenergy source and give a type of organism that uses each.Energy organismoxygenicphotosynthesischemosynthesisd) The following metabolism is incorrect as drawn.e-e- NADH + HNAD++energyATP ADP+ PiglucoseCO2O2H2Oi) Correct the error.ii) Explain why the metabolism is incorrect and why your correction fixes theproblem.iii) Circle the type of metabolism that the corrected diagram represents.Aerobic Respiration Anaerobic Respiration FermentationOxygenic Photosynthesis Anoxygenic Photosynthesis Chemosynthesis5Question 3Take the following simple ecosystem enclosed in a fish tank:••••••••phytoplanktonherbivorousfishwatergravelheterotrophicbacteria(one species)• the only energy input is light• the fish eat only the phytoplankton• humans harvest the fish• nothing eats the bacteria• the whole tank, including the sediments, is aerobica) Construct an energy flow model for this ecosystem.i) Label all compartments and productsii) assign a different label to each of the energy flowsiii) describe what each energy flow represents.b) Suppose you added a worm to this ecosystem that only consumes waste produced by thefish. What would be the effect on the level of respiration by the heterotrophic bacteria(increase, decrease, stay the same) of adding this worm to the tank, if the worm's waste anddetritus was not consumed by the detritivores. Explain your reasoning briefly.c) Suppose you added a worm to this ecosystem that only consumes waste produced by thefish. What would be the effect on bacterial respiration (increase, decrease, stay the same) ofadding this worm to the tank, if the worm's waste was consumed by the detritivores.Explain your reasoning briefly.6Question 4Nitrogen (in the form of nitrate: NO3–), and phosphorus (in the form of phosphate: PO43–),are often limiting nutrients in aquatic ecosystems. In the experiment below, you addphosphate fertilizer to a pond. You see a brief period of growth of most organismsfollowed by a large bloom of cyanobacteria. This is shown below:NO3– in H2Otime (weeks)PO43– in H2O organismscyanobacteria1 2biomass3 4Phosphate addedmosta) Which of the above element(s) are limiting at each of the following times?i) At time (1) ? Explain your reasoning.ii) At time (4) ? Explain your reasoning.b) Why is the [NO3–] in the water decreasing at time (2)?c) Why are the cyanobacteria at an advantage at time (4)?7Question 5You are studying the genetics of the fruit fly. Body color (brown or black) is controlled bythe b locus and wing size (long or short) is controlled by the vg locus. Use (+) for thealleles associated with the dominant characteristics, (b or vg) for the alleles associated withthe recessive traits.In cross 1, you mate two pure-breeding strains and obtain the following progeny:cross 1: brown, short-winged male X black, long-winged femaleF1: all brown, long-winged fliesa) Which phenotypes are dominant and which phenotypes are recessive?i) The recessive trait for body color is______________.ii) The recessive trait for wing size is______________.b) In cross 2, you then mate many pairs of siblings from the F1 generation of cross 1:cross 2: F1 sibling male X F1 sibling femaleWhat genotypic and phenotypic ratios would you expect in the progeny (F2) of thesecrosses if independent assortment occurs?The compiled progeny results from the cross 2 mating pairs are presented below:F2: Phenotype # identified brown, large-winged 512black, large-winged 244brown, short-winged 246black, short-winged 9c) From this data, what might you conclude


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MIT 7 014 - Quiz III

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