1 Exam 2 Biol 213-503 Molecular Cell Biology Fall 2009 Name__________________________________ In drawing structures, neatness counts. The space provided for each question should be sufficient for your answers. Note that there are 107 points on this exam but the maximum score you can receive is 100. Use your time wisely. Questions 1-18 are worth 3 points each. Circle your answer. 1. Where does most new membrane synthesis take place in a eukaryotic cell? (a) in the Golgi apparatus (b) in the endoplasmic reticulum (c) in the plasma membrane (d) in the mitochondria (e) on ribosomes 2. Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called _____________. (a) active transport (b) free diffusion (c) facilitated diffusion (d) passive transport 3. Ion channels (a) only open in response to a signal of some kind. (b) require input of energy in order to function. (c) have no limit to the rate at which they can transport ions. (d) can transport both negative and positive ions through the same channel. (e) allow passage of ions in both directions. 4. A yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process: C6H12O6 + 2ADP + 2Pi + H+  2CO2 + 2CH3CH2OH + 2ATP + 2H2O Unfortunately, the grape juice is contaminated with enzymes that attack some of the transport proteins in the yeast plasma membrane, and the yeast cell dies. Which of the following could account for the yeast cell’s demise? (a) Toxic buildup of carbon dioxide inside the cell (b) Toxic buildup of ATP inside the cell (c) Diffusion of ATP out of the cell (d) Inability to import sugar into the cell (e) Inability to take water into the cell 5. A gated ion channel _________ (a) stays continuously open when stimulated. (b) opens more frequently in response to a given stimulus. (c) opens more widely the stronger the stimulus. (d) remains closed if unstimulated.2 6. K+ leak channels are found in the plasma membrane. These channels open and close in an unregulated, random fashion. What do they accomplish in a resting cell? (a) They set the K+ concentration gradient to zero. (b) They set the membrane potential to zero. (c) They disrupt the resting membrane potential. (d) They do nothing in a resting cell. (e) They keep the electrochemical gradient for K+ at zero. 7. The action potential is a wave of ____ that rapidly spreads along the neuronal plasma membrane (a) sodium ions (b) neurotransmitters (c) hyperpolarization (d) electrochemical gradient (e) depolarization 8. Which of the following statements is FALSE? (a) NADH is more reduced than NAD+ (b) Oxidation of a molecule can occur in the absence of oxygen. (c) One turn of the citric acid cycle liberates two molecules of CO2. (d) The oxidation of one molecule of glucose during glycolysis yields one molecule of pyruvate. (e) none of the above. 9. The terminal electron acceptor from the mitochondrial electron transport chain is _______. (a) water (b) NAD+ (c) NADH (d) oxygen (e) NADP+ (f) none of the above 10. What is the net yield of ATP from the fermentation of one molecule of glucose? (a) 4 ATP (b) 2 ATP (c) 0 ATP (d) ~30 ATP (e) none of the above 11. Stage 1 of oxidative phosphorylation requires the movement of electrons along the electron-transport chain coupled to the pumping of protons into the intermembrane space. What is the final result of these electron transfers? (a) OH- is oxidized to O2. (b) Pyruvate is oxidized to CO2. (c) O2 is reduced to H2O. (d) H- is converted to H2. (e) O2 is converted to CO2. 12. In stage 1 of photosynthesis, a proton gradient is generated and ATP is synthesized. Where do protons become concentrated in the chloroplast? (a) thylakoid space (b) stroma (c) inner membrane (d) thylakoid membrane (e) matrix3 13. The final product of the Calvin cycle is ______. (a) water (b) oxygen (c) ribulose 1,5-bisphosphate (d) NADPH (e) glyceraldehyde 3-phosphate (f) glucose 14. Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes? (a) lateral movement (b) rotation (c) flexing of hydrocarbon chains (d) switching between lipid layers 15. The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is _________ (a) more free energy is released for a given amount of glucose oxidized. (b) no energy is lost as heat. (c) energy can be extracted in usable amounts. (d) more CO2 is produced for a given amount of glucose oxidized. (e) less O2 is required for a given amount of glucose oxidized. 16. What purpose is served by the phosphorylation of glucose to glucose 6-phosphate by the enzyme hexokinase as the first step in glycolysis? (a) It enables the glucose 6-phosphate to be recognized by aldolase, the next enzyme in the glycolytic pathway. (b) It generates a high-energy phosphate bond. (c) It converts ATP to a more useful form. (d) It helps drive the uptake of glucose from outside the cell. (e) It is the first committed step of glycolysis . 17. Which of the following statements about mitochondria is FALSE? (a) Protons are pumped from the intermembrane space into the matrix. (b) ATP is synthesized in the matrix. (c) Mitochondria contain DNA. (d) The outer membrane is permeable to protons. (e) The inner membrane is folded into cristae. 18. During glycolysis, phosphofructokinase mediates the following reaction: fructose 6-phosphate + ATP => fructose 1,6-bisphosphate + ADP + H+. Which of the following is an allosteric inhibitor of the reaction? (a) fructose 6-phosphate (b) ATP (c) fructose 1,6-bisphosphate (d) ADP (e) H+4 5 points (no partial credit will be awarded) 19. Indicate below how to prepare a 100 ml solution of HCl (strong acid) at pH 3.0 using a 200 mM stock solution of HCl and water. Express your answer using the indicated units. _______________________ ml of 200 mM HCl _______________________ ml of water 12 points total - 2 points each 20. For each of the enzymes listed below, name its cellular location (which compartment, membrane etc.). Assume all refer to eukaryotic organisms. Aldolase