1A?Bis2A/RothWinter 2011First Midterm ExamVersion A1. Which of the following treatments would leave a protein’s information contentunchanged?A. Removing all the “R” groups from amino acids.B. Rearranging the same amino acids in the sequenceC. Exchanging one amino acid for a different one.D. Denaturing the amino acid by heating.E. Hydrolyzing all of the peptide bonds.2. Two pyruvate molecules are produced from one molecule of glucose by glycolysis.What determines whether these pyruvates are reduced to lactate (or ethanol) or areoxidized by the TCA (Krebs) cycle?A. One pyruvate will always be reduced and the other will always enter into theTCA cycleB. Availability of CO2 allows use of TCA cycle.C. Availability of O2 or another outside respiratory electron acceptor allows use ofTCA cycle.D. High levels of NADH force pyruvate reduction; at low NADH levels oxidation ofpyruvate through the TCA cycle is allowed.E. TCA cycle is used if cells require a lot of energy.?3. *Which one of the following reactions is NOT an oxidation-reduction (redox) reaction?A. NADH 1/2O2 H <-> NAD H2OB. R-CH=CH-CH3 H2O <-> RCH2-CH(OH)-CH3C. FAD H2O <-> FADH2 1/2O2D. NADH acetaldehyde <-> NAD ethanolE. AH2 B <-> A BH2?4. What distinguishes photosynthesis (as done in plants) and aerobic respiration? (FILLTWO BUBBLES)A. One consumes CO2 the other produces CO2B. One uses light to excite electrons the other uses PMFC. One uses the ATPase to make ATP the other uses only substrate-linkedphosphorylation.D. One uses light to excite electrons the other uses the electron transport chainE. One produces O2 the other consumes O2?5. What makes an amino acid hydrophobic?A. polar R groupB. non-polar R groupC. positively charged R groupD. negatively charged R groupE. R group that disrupts protein secondary structure ?2A?6. What does a respiring heterotroph use as the proximal electron acceptor (first in theprocess of fuel oxidation)?A. NADHB. NAD C. NADP D. CO2E. O27. *The organisms that produced the oxygen gas in Earth’s atmosphere in ancient timeswere -A. Heterotrophic eukaryotesB. Autotrophic eukaryotesC. Autotrophic prokaryotesD. Heterotrophic prokaryotesE. Completely unlike any modern organisms8. A properly-folded protein tends to be globular with a hydrophobic (“greasy”) centerand an outer surface with exposed polar and charged R-groups. How is this structuregenerated? (Choose two contributing factors).(FILL TWO BUBBLES)A. Weak hydrogen bonds between O and H atoms of different peptide bondsgenerate secondary structure (string of wieners).B. Amino-acid R groups are rearranged in the sequence so that they all movetoward the center.C. Substrates and other proteins bind to the polar and charged R groups andholding them on the surface as the protein folds.D. Weak interactions between different R groups are formed and disrupted untilthe most stable structure is achieved.E. Hydrophobic (greasy) R-groups react to form covalent bonds that generate thesolid protein core.9. Biological communities around hydrothermal vents persist in the dark. This wouldseem to violate thermodynamics which requires some continuous outside energysource. How might these isolated communities live by standard redox chemistry?(FILL TWO BUBBLES)A. They can violate thermodynamics because of the high temperatures involved.B. They use as electron donors H2 H2S and other reduced compounds thatemerge from the vents.C. The communities use as fuel the biological deposits formed by earlierlife forms (oil deposits).D. They get oxygen that diffuses down to them from the surface atmosphere touse as an electron acceptor.E. They are autotrophs that use heat instead of light as a source of energy. ?3A?10. Suppose you believe that the first life form was an autotroph. Which of thefollowing lifestyles seems most likely?A. non-cyclic photosynthesizer (photo-autotroph)B. fermenterC. respirerD. a light-independent autotroph e.g using H2 to reduce CO2.E. cyclic photosynthesizerWe discussed a series of major biological metabolic inventions (the “toys oflife”) some of which are listed below.1. Substrate-linked phosphorylation (e. g. G3PO4 dehydrogenase).2. Electron transport – using redox reactions to pump protons)3. ATPsyntase (interconverting PMF and ATP)4. Photo-center (using light to excite an electron5. TCA cycle (oxidizing pyruvate to CO2 and H2O)6. Rhodopsin (direct pumping of protons by light)7. Splitting water to release oxygen and reducing power.8. Fixing CO2 using Rubisco??Use the toy numbers above to answer the questions below?11. Which of the above toys is the source of ATP for a fermenting organism.A. Combination of 1 and 3B. Toy number 5C. Combination 2 and 3.D. Exclusively toy 1E. Use toy 2 in combination with an outside electron acceptor12. What form of metabolism uses toys 2 3 4 and 7?A. Aerobic respirationB. Photo-autotrophyC. Cyclic photosynthsisD. Anerobic respirationE. Light independent heterotroph (e.g. methanogen)13. During aerobic respiration electrons are taken from NADH (H ) ?transported by a multi-step pathway and then used to reduce O2 to H2O.?Why not save all these steps and use NADH to reduce O2 directly??A. This has occurred in humans which have a streamlined metabolism. ?B. This would release energy in a way that it could not be used to do work.?C. The single step is energetically unfavorable?D. A single step would not be reversible ?E. Both (A) and (D) are correct ?4A?14. What organism obtains small carbon-containing molecules for biosynthesis byOXIDIZING an outside carbon-containing compound ??A. a respiring heterotroph?B. a fermenting heterotroph?C. a photosynthesizing autotroph?D. A and B?E. A and C15. What organism gets small carbon-containing molecules for biosynthesis byREDUCING an outside carbon compound? ?A. a respiring heterotroph?B. a fermenting heterotroph?C. a photosynthesizing autotroph?D. A and B?E. A and C16. ATP has two high-energy phospho-diester bonds (labeled I and II in the figurebelow) and can use them to carry energy to a variety of reactions.IIIPO4-PO3-PO3-Ribose-AdenineEnergy is usually delivered by hydrolyzing the outside bond (I) producing ADP PO4. In some reactions however the inside bond (II) is hydrolyzed producing AMP PO3-O-PO3. In what sorts of reactions do you think the insidebond (II) might by hydrolyzed? (FILL TWO BUBBLES)A. When the cell has too much free phosphate.B. For reactions that are highly unfavorable and need more energy.C. When it’s essential to assure that the reaction does not go in reverse.D. When small doses of energy are needed.E. At low temperature when all reactions are moving slowly and the cell needsthe added energy to attain a sufficient reaction rate.17. *The immediate source of energy for ATP synthesis in chloroplasts andphotosynthetic bacteria is–A. Electron transportB. The electrochemical proton gradient (PMF)C. LightD. Energized chlorophyllsE. NADPH ?5A?The figure above presents the effects of substrate concentration heat and on the rate ofa particular reaction. Answer the questions below by filling in the bubble correspondingto one of the letters (A B C D E) in the figure.18.Which line gives evidence that the catalyst can be saturated? (A B C D E ?)19.Which line is most likely to describe an enzyme-catalyzed reaction? (A B C D E?)20. What aspect of the data can be used to estimate of the catalytic efficiency( reaction rate of catalyst-bound molecules)?A. The maximum initial slope of line A.B. The rate approached by line A at high substrate concentrations (Vmax).C. Half the reaction rate Vmax in line AD. The ratio of the reaction rate in line B to the initial rate of line A.E. The reaction rate seen in line C just before it drops.21. What aspect of the data can be used to estimate of the binding affinity ofsubstrate for the catalyst?A. The concentration at which Vmax is achievedB. The reaction rate seen at the lowest substrate concentration.C. The concentration at which the reaction rate reaches ½ of Vmax.D. The concentration that just begins to inhibit the reaction rate (line A).E. The substrate concentration just at the point that temperature causes arate drop in line C. ?6A?In the figure above the letters A B C D E represent values that can be used?to answer the questions below.22.Which TWO values are NOT affected by heat? (FILL IN TWO BUBBLES)23Which TWO values are affected by BOTH heat AND catalysis?24Which value would be changed by a catalyst but not by heat?25Which SINGLE value dictates the forward rate constant (kF) with andwithout a catalyst?26Which SINGLE value determines the ratio of reactant concentrations(PxQ)/(MxN) at equilibrium?27.What SINGLE value has no effect on the reaction rate even far from equilibrium?28What is the effect of a catalyst on the reaction described in the figure?A. It increases the forward rate constant but not the back rate constantB. Changes the steady state concentration of reactants such that thereaction becomes more favorable (more P Q less M N at equilibrium).C. Reduces barriers to both forward and backward reaction by lowering thetransition state energy.D. Specifically increases the forward reaction rate by reducing the FORWARDactivation energy .E. The catalyst has very little effect in this reaction because the transition stateis so high.29. *What are the products of non-cyclic photosynthesis (systems I II) in plants andcyanobacteria? (ONE BUBBLE)A. ATPB. NADP and ATPC. NADPH and ATPD. NADPH O2 and ATPE. NADP O2 and ATP ?30. *Which of the following statements is INCONSISTENT with the first andsecond laws of thermodynamics?A. Living organisms can create energyB. Chemical energy can be converted to light energyC. The total energy of a system is available to do work.D. Potential energy may be used to do work.E. both A and C.31. Most biological metabolic reactions proceed at an extremely slow rate in theabsence of a catalyst. Choose two ways to explain why this happens(mechanistically or functionally). (FILL TWO BUBBLES)A. The transition state energy of these reactions is much higher than the energy ofthe substrates so the rate constants are extremely tiny without a catalyst.B. In the confined space within a cell products get concentrated and thereactions come rapidly to steady state.C. Metabolism is only possible if the rates of useful reactions exceed the rates ofthe large array of other reactions. Life can dictate its metabolism only bydeveloping catalysis.D. The catalysts do increase reaction rates but the measured uncatalyzed ratesare much faster than they would need to be for a cell to function.E. The catalysts are required because they allow more energy to be obtainedfrom poor fuel molecules.32. The figure shows an alpha helix located in the middleof a folded protein. How is the depicted portion oriented?A. Amino terminus at the bottomB. Amino terminus at the topC. A protein has an amino terminus at both ends.D. The orientation of a protein cannot be determined from theamount of molecular structure shown.E. The orientation can only be determined if you see thestructure of one end of the protein.33. What does non-cyclic photosynthesis achievethat can not be provided by a cyclic photosynthsizer? (FILL TWO BUBBLES)A. Formation of PMFB. Formation ATPC. A source of reducing power for biosynthesis.D. The ability to return excited electrons to its own photo-centerE. Ability to fix CO2.7A
