BL 424 Test 2 2010 150 pts name ________________________ Multiple choice have one answer and are worth 3 points each. 1. In translation, mRNAs are read in the _______ direction, and polypeptide chains are synthesized from the _______ends. a. 5′ to 3′; amino to the carboxyl b. 5′ to 3′; carboxyl to the amino c. 3′ to 5′; carboxyl to the amino d. 3′ to 5′; amino to the carboxyl 2. Export of RNAs from the nucleus occurs primarily by a. passive diffusion through nuclear pore complexes. b. cotranscriptional insertion through nuclear envelope membrane protein pores. c. selective transport through nuclear pore complexes in association with proteins. d. release from the nucleus when it breaks down at mitosis. 3. Most eukaryotic plasma membrane proteins are synthesized on a. ribosomes associated with the plasma membrane and inserted into the membrane cotranslationally b. free ribosomes; inserted after translation into the plasma membrane. c. rough ER ribosomes; carried to the plasma membrane by vesicles that pinch off from the Golgi. d. rough ER ribosomes; carried to the plasma membrane by vesicles that pinch off from the rough ER. 4. Which of the following proteins does not pass through the Golgi apparatus? a. Lysosomal enzymes b. Ribosomal proteins c. Cell surface proteins d. Secreted proteins 5. Mitochondrial and chloroplast proteins are synthesized on a. ER ribosomes. b. free cytosolic ribosomes. c. organellar ribosomes. d. Both b and c 6. The function of peroxisomes is to a. oxidize certain organic molecules and degrade the H2O2 produced by these reactions. b. reduce certain organic molecules using H2O2. c. produce hydrogen peroxide for cells. d. degrade old organelles. 7. Intermediate filaments function in a. cell motility. b. providing mechanical strength for cells. c. nuclear pore structure. d. All of the above 8. The beating of cilia and flagella occurs by means of _______-based _______. a. dynein; microtubule sliding b. kinesin; microtubule sliding c. myosin; microfilament sliding d. tubulin; microtubule contraction 9. The concentration of actin monomers at which the rate of polymerization into filaments equals the rate of depolymerization is called the _______ concentration. a. equilibrium b. dynamic c. steady-state d. treadmilling10. The primary function of the mitochondrion is production of ATP. To carry out this function, the mitochondrion must have all of the following EXCEPT: a. mitochondrial ATP synthase b. membrane-bound electron transport chain c. enzymes for glycolysis d. enzymes for the Krebs (citric acid) cycle 11. The nuclear envelope is continuous with the a. mitochondrial outer membrane. b. rough endoplasmic reticulum. c. Golgi apparatus. d. plasma membrane. 12. ATP is hydrolyzed by actin a. in the process of assembly into a filament. b. after assembly but before disassembly. c. in the process of disassociation. d. after disassociation from the filament. 13. Myosin _______ is present in muscle sarcomeres. a. I b. II c. III d. IV e. V 14. Energy molecules involved with actin polymerization microtubule polymerization. a. Both actin and tubulin dimers bind ATP b. Both actin and tubulin dimers bind GTP c. Actin binds ATP, tubulin dimers bind GTP d. Actin binds GTP, tubulin dimers bind ATP 15. Which of the following is not one of the functions of the cytoskeleton? a. To provide a structural framework for the cell b. Cell locomotion c. Protein translocation into the ER d. Intracellular movement of organelles and other structures 16. Where are phospholipids in mitochondrial membranes such as phosphatidylcholine and phosphatidylethanolamine synthesized? a. In the ER b. The intermembrane space c. The cytosolic side of the outer membrane d. The lumenal side of the inner membrane 17. Human diseases caused by mutations in mitochondrial genomes a. are inherited from both parents. b. are inherited from the father. c. are inherited from the mother. d. do not exist because the mutation is always complemented by the normal gene copy in the nucleus. 18. The human mitochondrial genome encodes 13 proteins (respiration complex), while the nuclear genome encodes 1000 proteins expressed in the mitochondrion. The % encoded in Mt genome: a. 0.013% b. 0.13% c. 1.3% d. 13%19. Most mitochondrial proteins are synthesized on a. mitochondrial ribosomes from nuclear mRNAs. b. cytoplasmic ribosomes; they are imported cotranslationally as they are being synthesized. c. cytoplasmic ribosomes; they are imported after they are completely synthesized. d. mitochondrial ribosomes from mitochondrial mRNAs. 20. (One model holds that the specificity of a vesicle fusing with its target membrane lies in the interaction of pairs of proteins called v-(vesicle) and t-(target) a. SNAP b. SNAREs c. NSFs d. COPIs 21. In plant cells, vesicles transport proteins from the Golgi apparatus to a. lysosomes b. vacuoles c. chloroplasts d. mitochondria 22. The red blood cell been such a good model system for studying cytoskeleton because: a. it had no nucleus b. it does not have endoplasmic reticulum or golgi c. it does not have intermediate filaments or microtubules d. all of the above 23. Nuclear localization signals (NLS) are not cleaved from proteins after import into the nucleus because NLSs a. target proteins to specific locations within the nucleus b. are used to reimport nuclear proteins after mitosis c. bind to DNA and regulate genes d. all of the above 24. (12 pts) Matching enzymes. One choice each. Choices are used only once. ____ aminoacyl tRNA synthetase a. adds sugars to proteins ____ flippase b. removes sugars from proteins ____ glycosidase c. complex that degrades ubiquitinated proteins ____ proteasome d. attaches amino acids to specific tRNAs ____ myosin light chain kinase e. translocates lipids across bilayer membrane ____ signal peptidase f. phosphorylates myosin II g. cleaves specific sequence off proteins in ER 25. (10 pts) Protein targeting sequences. You have a plasmid encoding Green fluorescent protein (GFP) expressed from a eukaryotic promoter. To construct a series of different plasmids, each targeting GFP protein to a different compartment, which gene sequences will target GFP? One choice each. a. transit peptide sequence ____ into ER from ribosome b. presequence ____ protein degradation