BCMB 8020 Exam III Name _____________________________ Dr. Schmidt’s Lectures (100 points total) April 5, 2005 True / False (1/2 point each; 10 points total) 1. With respect to a pure lipid membrane, ___ water crosses more efficiently than glucose. ___ ions cross more efficiently than glucose. 2. The flow of water across a biological membrane is: ____ regulated by the opening and closing of water channels. ____ correlates with ion flow. 3. Phosphorylation enhances: ____ the polarity of the modified side chain. ____ ionic interactions with glutamate and aspartate side chains. 4. SCF-type E3 ligases: ____ bind phosphorylated substrates. ____ are covalently modified with ubiquitin. 5. Facilitated transport: ____ is typically highly specific with respect to cargo. ____ can involve the transport of molecules up their concentration gradients. 6. Porins: ____ have a larger pore size than water channels. ____ are found on the inner membrane of Gram-negative bacteria. 7. Type I bacterial secretion: ____ is mechanistically similar to ER translocation. ____ involves the action of an ABC transporter. 8. Regarding protein-protein interaction domains: ____ PH domains bind phosphoserine residues. ____ SH2 domains bind phosphotyrosine residues. 9. Regarding the use of radiolabeled azido-ATP to probe enzyme function: ____ kinase substrates can be labeled using 32P(γ)-ATP. ____ ATPases can be labeled using 32P(γ)-ATP. 10. Requirements for the application of FRET include: ____ fluorophores that emit at different wavelengths. ____ physical interaction between the fluorophores.BCMB 8020 Exam III Name _____________________________ 2 Multiple Choice (2 points each; 20 points total) 11. Based on the analogies presented in class, where proteins are represented by plants and lipids by water, a biological membrane is most like a: A) a dense forest with a few pools of water B) a grassland with the occasional lake and river C) a swamp with waterways, bogs and small forested islands D) a sea dotted with the occasional forested island 12. All of the following are key characteristics of plasma membranes, except for: A) they are composed of lipids, proteins and carbohydrates B) they have similar ratios of lipids, proteins and carbohydrates from organism to organism C) the leaflets of the bilayer are asymmetric in composition D) they are generally permeable to ions 13. Which of the following amino acids would you expect to find, more likely than the others, in a transmembrane segment? A) glutamate B) leucine C) lysine D) serine 14. All of the following are hallmarks of eukaryotic secretory signal sequences, except for: A) they have a tripartite composition B) they interact with RNA C) they are proteolytically cleaved at two or more sites D) they target proteins to an ABC-type transporter on the ER 15. P-type transporters are phosphorylated on which of the following residues during their catalytic cycle? A) aspartate B) cysteine C) serine D) tyrosine 16. Which of the following proteolytic mechanisms does not require a water nucleophile during the hydrolytic cycle? A) aspartate B) cysteine C) metallo D) serineBCMB 8020 Exam III Name _____________________________ 3 17. As a group, ABC transporters exhibit which one of the following characteristics: A) they can transport a variety of substrates B) they function only in the import of molecules C) they are smaller than the average 30 kDa protein D) they can be composed of four identical subunits 18. All of the following can occur during the transport of ions via channels, except for: A) desolvation B) transport of cargo down a concentration gradient C) weak interactions with carbonyl atoms of helices that line the channel D) generation of electrochemical gradients 19. The following are features of GPCR systems, except for: A) they are used for transducing extracellular signals to the inside of the cell B) they require a peptide ligand C) they require a receptor that has multiple membrane spans D) they are coupled to trimeric G-proteins 20. All of the following contain a fatty acid component, except for: A) sphingolipids B) prostoglandins C) GPI proteins D) isoprenylated proteins Short Answer - These can be answered using one or two keywords, diagrams, and/or a short sentence (2-5 points each; 36 points total) 21. Draw the stick figure chemical structure of a 16:1(∆9) fatty acid. (4 points)BCMB 8020 Exam III Name _____________________________ 4 22. Draw the chemical structure of an activated isoprene. (3 points) 23. What radiolabeled precursor would you use to specifically radiolabel the following: (1 point each) a) all lipids. b) fatty acid-based lipids, to the exclusion of isoprene-based lipids c) glycerophospholipids and triacylglycerol, to the exclusion of other lipids. d) sphingolipids. 24. Historically, why have phosphohistidine residues been difficult to detect? (2 points) 25. If a protein has a PH domain, where is the likely subcellular localization of this protein. (2 points)BCMB 8020 Exam III Name _____________________________ 5 26. Fatty acids have relatively low solubility in aqueous solutions. What facilitates the circulation of fatty acids in the blood? (2 points) 27. Of the four proteolytic mechanisms, which involve the formation of a covalent intermediate between the protease and its substrate? (2 points) 28. List the representative groups of lipid molecules that can be found covalently attached to proteins? (5 points) 29. As discussed in class, list the four key events associated with signal transduction in whole cells. (4 points) 30. List the post-translational modifications associated with regulation of IkB function and the resultant effect of these modifications. (4 points) 31. What is the purpose of a PDZ domain? (2 points) 32. What structural feature of chymotrypsin explains why it is inhibited by TPCK but not TLCK. (2 points)BCMB 8020 Exam III Name _____________________________ 6 Long Answer - answer the following questions using several sentences and/or diagrams. (4-8 points each; 34 points total) 33. Describe the general events associated with NFκB activation? (6 points) 34. Outline or diagram the general steps associated with SREBP-mediated cholesterol homeostasis. (8 points)BCMB