Exam 2 Biol 213 Molecular Cell Biology Fall 2012 Name__________________________________ The use of calculators is prohibited on this exam. The space provided for each question should be sufficient for your answers. Note that there are 102 points on this exam but the maximum score you can receive is 100. Use your time wisely. Questions 1-11 are worth 3 points each. Circle your answer. 1. Even in the presence of oxygen, cancer cells typically generate all of their ATP through glycolysis followed by lactic acid fermentation. Fermentation is used to regenerate which essential molecule: (a) O2 (b) ethanol (c) NAD+ (d) NADP+ (e) NADH 2. Oxidative phosphorylation requires an electron-transport chain that operates on high-energy electrons taken from the activated carrier molecules. Which transporter is the initial electron acceptor from NADH? (a) NADH dehydrogenase (b) Cytochrome C (c) Cytochrome BC1 complex (d) Cytochrome oxidase (e) Ubiquinone 3. When high-energy electrons are transferred through a series of molecules in the electron-transport chain, the energy released during these transfers is used to generate a gradient of________. (a) protons (b) K+ (c) Na+ (d) Cl- 4. During respiration, energy is retrieved from the high-energy bonds found in certain organic molecules. Which of the following, in addition to energy, are the ultimate products of respiration? (a) CO2, H2O (b) CH3, H2O (c) CH2OH, O2 (d) CO2, O2 (e) O2, H2O 5. Mitochondria and chloroplasts both have electron transport systems. Name the molecule that serves as the terminal electron acceptor for each (mitochondria, chloroplast): (a) O2, NADP+ (b) O2, NAD+ (c) H2O, NADP+ (d) H2O, NAD+ (e) CO2, O26. The action potential is a wave of ____ that rapidly spreads along the neuronal plasma membrane (a) depolarization (b) sodium ions (c) neurotransmitters (d) hyperpolarization (e) electrochemical gradient 7. Voltage-gated channels contain charged protein domains, which are sensitive to changes in membrane potential. By responding to a threshold in the membrane potential, these voltage sensors trigger the opening of the channels. Which of the following best describes the behavior of a population of channels exposed to such a threshold? (a) All channels open partly, each to a different degree. (b) All channels open completely. (c) All channels open partly, to the same degree. (d) Some channels remain closed and some open completely. 8. Which of the following statements is FALSE? (a) Glucose releases more energy when it is enzymatically broken down to CO2 and water than when it is burned. (b) NADH is more reduced than NAD+ (c) Oxidation of a molecule can occur in the absence of oxygen. (d) One turn of the citric acid cycle liberates two molecules of CO2. (e) none of the above. 9. In stage 1 of photosynthesis, a proton gradient is generated and ATP is synthesized. Where do protons become concentrated in the chloroplast? (a) stroma (b) inner membrane (c) thylakoid space (d) thylakoid membrane (e) matrix 10. Three phospholipids X, Y, and Z are distributed in the plasma membrane as indicated in the figure below. For which of these phospholipids does a flippase probably exist? (a) X only (b) Z only (c) X and Y (d) Y and Z X X X Y X Y Y Y X Y X YZZYZ ZZYZZYYYextracellular spacecytosol11. During glycolysis, phosphofructokinase is a key regulatory step that mediates the following reaction: fructose 6-phosphate + ATP => fructose 1,6-bisphosphate + ADP + H+. Which of the following is an allosteric activator of the reaction? (a) fructose 6-phosphate (b) ATP (c) fructose 1,6-bisphosphate (d) ADP (e) H+ 5 points (1 pt each) 12. Circle the molecule in each pair that is more likely to diffuse through the lipid bilayer. A. serine or benzene B. CO2 or water C. glycerol or RNA D. H2O or O2 E. adenosine or sodium ion 8 pts (4 for part A; 4 for part B) 13. A. Rank in the left column the following compounds according to the total amount of energy a cell can harvest during a complete aerobic metabolism. (1=most to 5=least; pyruvate is rank 2) B. Complete the remaining portion of the table by indicating which metabolic pathways are utilized to recover the maximum energy from each compound. Check the appropriate box(es). The answer to pyruvate is shown. It is the molecule in the table with the second most energy. Rank (1-5) compound Glycolysis TCA cycle Electron transport chain and Oxidative Phosphorylation 2 pyruvate X X Acetyl-CoA FADH2 Glucose NADH6 points (no partial credit will be awarded) 14. Indicate below how to prepare 1 liter of a 100 mM UR2+ solution at pH 2.0 using dry UR2+ powder (100 g/mole), a 1 M HCl (strong acid) stock solution and water. Be sure to clearly indicate units. UR2+: ______________________ 1 M HCl stock: _________________ Water: ________________________ 4 points 15. List four (and only four) types of evidence that support the theory that mitochondria and chloroplasts evolved from free-living microorganisms (Endosymbiotic Theory).12 points (2 points for each enzyme) 16. For each of the enzymes listed below, name its cellular location (which compartment, membrane etc.). Assume all refer to eukaryotic organisms. Citrate synthase (acetylCoA + oxaloacetate → citrate + HS-CoA) location: __________________________________________________ Cytochrome oxidase (O2 + 4H+ → 2H2O) location: __________________________________________________ Hexokinase (glucose + ATP → Glucose 6-P + ADP) location: __________________________________________________ Phosphofructokinase (fructose 6-P + ATP → fructose 1,6-bisphosphate + ADP) location: __________________________________________________ Rubisco (CO2 + ribulose 1,5-bisphosphate → 2x 3-phosphoglycerate) location: __________________________________________________ Water-splitting enzyme (2H2O → 4H+ + O2) location: __________________________________________________10 pts. 17. You are comparing how fructose is transported into two different types of bacterial cells. You expose both cell types to a single concentration of fructose then measure the rate of transport based on accumulation in the cells. Cell type #1 accumulates fructose rapidly until the concentration inside the cell is essentially equal to that outside the cell. Cell type #2 accumulates fructose at