1 Exam 4/Final Biol 213 Molecular Cell Biology Fall 2011 Neatly printed name_______________________________________ Signature________________________________ Please note that there are 163 points on this exam but the maximum score you can receive is 150. The space provided for each question should be sufficient for your answers. Questions 1-20 are worth 3 points each. Circle your answer. 1. Cystic fibrosis is caused by (a) abnormal cell proliferation. (b) a defective DNA polymerase. (c) a defect in RNA processing. (d) a bacterial or fungal infection. (e) misfolding of a chloride channel. 2. You are doing a molecular cell biology experiment, studying why the Mit3 protein is located in the mitochondria. You mutate amino acid 23 of Mit3 from a valine to a threonine. The mutant Mit3 protein is now cytosolic. This indicates that (a) Valine 23 is sufficient for Mit3 localization in the mitochondria. (b) Valine 23 is necessary and sufficient for Mit3 localization in the mitochondria. (c) Valine 23 is necessary for Mit3 localization in the mitochondria. (d) Valine 23 is neither necessary nor sufficient for Mit3 localization in the mitochondria. (e) Valine 23 is not necessary for Mit3 localization in the mitochondria. 3. Disulfide bonds in proteins are first formed (a) in the cytosol. (b) in the Golgi. (c) in the endoplasmic reticulum. (d) in transport vesicles. (e) only after proteins such as transcription factors have entered the nucleus. 4. You are studying a protein and find that the molecular weight is 63 kDa. You get part of the amino acid sequence of the protein, and from that identify the gene that encodes the protein. Oddly, the gene encodes a protein with a predicted mass of 47 kDa, and you suspect that the protein must be glycosylated to account for the missing mass. Treatment of the protein with deglycosylating enzymes reduces the mass, showing that the protein is indeed glycosylated. Glycosylated proteins tend to be found in (a) the cytosol. (b) the nucleus. (c) the plasma membrane or secreted. (c) bacteria. (d) the mitochondrial matrix. 5. A defect in keratin filaments would most likely cause (a) poor cell-cell adhesion. (b) poor cell motility. (c) defects in cytokinesis. (d) defects in mitosis. (e) defects in RNA processing.2 6. You are a family physician in a small town and notice that in the space of three years, two cousins both suddenly died of hypertrophic cardiomyopathy; one died at the age of 19 while playing baseball, the other died at 18 while out jogging. After doing echocardiograms, it would be wise to (a) test other family members for mutations in cardiac actin. (b) test other family members for mutations in cardiac myosin. (c) test other family members for mutations in cardiac troponins. (d) both a and b. (e) both a, b, and c. 7. A very characteristic feature of G protein coupled receptors is that they (a) have just 1 transmembrane domain. (b) are cytosolic. (c) have 6 transmembrane domains. (d) have 7 transmembrane domains. (e) have 12 transmembrane domains. 8. G proteins can bind (a) just GTP. (b) just GDP. (c) just GMP. (d) both a and b. (e) both a, b, and c. 9. Adenylyl cyclase converts (a) ATP to cAMP. (b) ADP to cAMP. (c) AMP to cAMP. (d) cGMP to cAMP (e) cATP to cAMP. 10. Insulin activates (a) a G protein receptor to make cAMP. (b) a G protein receptor to make IP3. (c) a G protein receptor to make cGMP. (d) a G protein receptor to make DAG. (e) a tyrosine kinase receptor. 11. The Ras protein is active when (a) it has bound cAMP. (b) it has bound cGMP. (c) it has bound GDP. (d) it has bound GTP. (e) it is released into the cytosol. 12. In dividing cells, one would expect to observe rhythmic levels of (a) M and S cyclin proteins. (b) M phase CDK proteins and S phase CDK proteins. (c) M cyclins but not S cyclins. (d) S cyclins but not M cyclins. (e) just the phosphorylation states of the M and S cyclins.3 13. The presence of severely damaged DNA in a cell (a) activates kinases but not proteases. (b) activates kinases and proteases. (c) activates proteases but not kinases. (d) activates phosphatases but not proteases. (e) activates phosphatases and proteases. 14. If you could put an extra copy of the p53 gene in a tumor cell, you would expect to observe that (a) the cells proliferate faster. (b) nothing happens – the cells keep proliferating. (c) the cells would invariably stop proliferating. (d) the cells may stop proliferating, or that nothing happens. (e) the cells will invariably undergo apoptosis. 15. Mutations in genes encoding which of the following types of proteins are generally NOT associated with tumors? (a) apoptosis (b) signal transduction (c) cell adhesion (d) cell motility (e) microtubules 16. 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 (unstimulated) cell? (a) They set the K+ concentration gradient to zero. (b) They disrupt the resting membrane potential. (c) They set the membrane potential to zero. (d) They do nothing in a resting cell. (e) They keep the electrochemical gradient for K+ at zero. 17. Oxidizing glucose via multiple steps, as in cellular respiration, compared with its combustion to CO2 and H2O in a single step provides what advantage to a cell? (a) More free energy is released for a given amount of glucose oxidized. (b) Energy can be extracted in usable amounts. (c) More CO2 is produced for a given amount of glucose oxidized. (d) No energy is lost as heat. (e) Less O2 is required for a given amount of glucose oxidized. 18. Any reaction A ⇔ B is at equilibrium when (a) [A] = [B]. (b) ΔG ° = 0. (c) ΔG = ΔG °. (d) RT = 0.616 (e) ΔG = 0. 19. Which of the following statements is FALSE? (a) Proteins are designed to bind their ligands as tightly as possible. (b) The three dimensional structure of a protein dictates its function by determining its binding specificity for other molecules. (c) Many proteins have more than one binding site. (d) Binding between protein and ligand generally involves noncovalent bonds. (e) Changes in the amino acid sequence of a protein can decrease binding to a ligand, even if the altered amino acid does not lie in the binding site for the ligand.4 20. A bacterium is suddenly expelled from a warm human intestine