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University of Arizona
Ecology & Evolutionary Biology

MCB 181 005/6 Exam 2 KEY Lyons/Beilstein 150 pts. Questions are equally weighted 1. Which of the following statements represents a major difference between prokaryotic cells and eukaryotic cells? A. Eukaryotes have cells while prokaryotes do not. B. Eukaryotes are generally larger in size than prokaryotes. C. Eukaryotic cells tend to have much more extensive inner membrane systems and larger numbers of intracellular organelles than do prokaryotes. D. Prokaryotes are not able to carry out aerobic respiration, a process that requires a complex inner-membrane system. E. both B and C (E) Definition. 2. The small intestine is the site of digestion and absorption of nutrients. A single layer of epithelial cells lines the small intestine. In the duodenum (the first section of the small intestine), these epithelial cells secrete large quantities of digestive enzymes into the digestive tract. Which of the following features would you expect to find in these epithelial cells? A. They would have an expanded nucleolus. B. They would contain large quantities of rough endoplasmic reticulum. C. They would have larger nuclei than cells that secrete large quantities of lipids. D. They would contain large numbers of lysosomes. E. They would have more smooth endoplasmic reticulum than rough endoplasmic reticulum. (B) Site of protein synthesis. 3. You have a distant cousin, age 5, who is always tired and fatigued and is not able to play games and sports like other healthy children. He most likely has an enzyme deficiency or defect associated with which intracellular organelle? A. Golgi apparatus B. mitochondria C. ribosomes D. lysosomes E. smooth endoplasmic reticulum (B) Mitochondria is site of ATP synthesis, ATP is energy currency of the cell. 4. Amoebae move by crawling over a surface (cell crawling). Which one of the following processes is part of this type of movement? A. reinforcing the pseudopod with intermediate filaments B. setting up microtubule extensions that vesicles can follow in the movement of cytoplasm C. growth of actin filaments to form bulges in the plasma membrane D. cytoplasmic streaming E. Both B and C (C) Cell crawling is due to actin and myosin. 5. Researchers tried to explain how vesicular transport occurs in cells by attempting to assemble the transport components. They set up microtubular tracks along which vesicles could be transported, and they added vesicles and ATP (because they knew the transport process requires energy). Yet, when they put everything together, there was no movement or transport of vesicles. What was missing? A. mitochondria B. an axon C. myosin D. contractile microfilaments E. motor proteins (E) Microtubules use motor proteins such as dynein. 6. Viruses use the host's machinery to make copies of themselves. However, some human viruses, like dengue, require a type of replication that humans do not normally do. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires? A. Viruses can stay in a quiescent state until the host cell evolves this ability. B. The virus infects only those cells and species that can perform all the replication roles necessary. C. The virus has in its own genome the code for any specialized enzymes that the host does not have. D. The virus causes mutations in the human cells, resulting in the formation of new enzymes that are capable of performing these roles. E. The virus actually infects bacteria living inside the human body. (C) Viral genome encodes proteins for reverse transcription. 7. Which of the following best illustrates the order of events that occurs during a viral infection? A. (1) entry; (2) replication of viral genome; (3) transcription; (4) production of viral proteins; (5) assembly of new virions B. (1) entry; (2) production of viral proteins; (3) replication of viral genome; (4) transcription; (5) assembly of new virions C. (1) entry; (2) transcription; (3) production of viral proteins; (4) replication of viral genome; (5) assembly of new virions D. (1) entry; (2) production of viral proteins; (3) transcription; (4) replication of viral genome; (5) assembly of new virions E. none of the above accurately illustrates the order of events during viral infection (C) 8. Which statement best explains why the existence of multiple steps in a signal transduction pathway allows it to be regulated by several other pathways? A. Multiple steps allow the signal to be amplified. B. Multiple steps provide a series of points where hormone can bind. C. Multiple steps convert the signal from one form to another. D. Multiple steps provide a series of points where cross-talk can occur. E. Multiple steps increases the number of targets in the nucleus. (D) Cross talk occurs when signaling pathways interact. The more steps in the pathway, the more opportunity for cross-talk. 9. The most abundant protein found in the extracellular matrix of animal cells is _____. A. collagen B. pectin C. cellulose D. hemoglobin E. integrin (A) ECM definition 10. Which of the following statements most accurately describes the function of plasmodesmata in plant cells or gap junctions in animal cells? A. Gap junctions allow passage of proteins and small molecules between adjacent cells. B. Plasmodesmata allow passage of proteins and small molecules between adjacent cells. C. Plasmodesmata allow passage of only proteins between adjacent cells. D. Gap junctions allow passage of only proteins between adjacent cells. E. Both gap junctions and plasmodesmata allow passage of proteins and small molecules between adjacent cells. (B) Plasmodesmata allow proteins to pass, gap junctions do not. 11. Put the steps of the process of signal transduction in the order they occur: 1. A conformational change in the signal-receptor complex activates an enzyme. 2. Protein kinases are activated. 3. A signal molecule binds to a receptor. 4. Target proteins are phosphorylated. 5. Second messenger molecules are released. A. 3, 1, 2, 4, 5 B. 3, 1, 5, 2, 4 C. 1, 2, 5, 3, 4 D. 1, 2, 3, 4, 5 E. 3, 5, 1, 2, 4 (A) or (B) 12. A G-protein receptor with GTP bound to it _____. A. signals a protein to maintain its shape and conformation B. directly affects gene expression C. will use cGMP as a second messenger D. is in its active state E. is in an inactive state (D) 13. Blood sugar is regulated by two pancreatic hormones, insulin and glucagon. When blood sugar rises, insulin is released; it binds to receptors and, through signal transduction, results in an increase in glucose uptake by cells, which effectively lowers blood glucose levels. When blood sugar decreases, glucagon is released, binds to cell receptors, and causes glucose to be released into circulation, thereby increasing blood glucose levels. Diabetes mellitus is a disorder that results from excessively high levels of blood glucose. Type II diabetics have normal to elevated levels of insulin. What, then, might be causing their elevated blood glucose levels? A. defective receptors B. defective second messenger C. overproduction of glucagon D. inadequate insulin production E. none of the above reasons explain what might be causing elevated blood glucose levels (A) Defective receptors are unable to receive the signal from insulin, which would result in glucose uptake by cells, thereby reducing blood glucose levels. 14. Which of the following statements is (are) inconsistent with the first and second laws of thermodynamics? A. Living organisms can produce energy. B. Chemical energy may be converted to light energy. C. The total energy of a system is available to do work. D. Potential energy may be used to do work. E. Both a and c (E) 15. Which of the following statements concerning energy transformations is true? A. Increases in entropy reduce usable energy. B. Energy may be created during transformation. C. Potential energy increases with each transformation. D. Increases in temperature decrease total amount of energy available. E. Decreases in entropy reduce usable energy (A) 16. When NAD is converted to NADH it is _____; When FADH is conve2ted to FAD it is ____. Of these four molecules, _____ stores the most energy for use in oxidative phosphorylation. A. Reduced; Oxidized; FADH 2 B. Oxidized; Reduced; NADH C. Reduced; Oxidized; NADH D. Oxidized; Reduced; FADH 2 E. None of the above (C) The following three questions refer to the above diagram which depicts a metabolic pathway with substrates, intermediates and products indicated with letters A-I, and the enzymes mediating the reactions indicated with numbers 1-8. 17. If enzyme 2 is inactive, which of the following products would be produced from the metabolic pathway? A. A and B B. C and G C. C and D D. E and F E. None of the above (A) or (E) 18. Negative feedback regulation of synthesis of product I most likely involves _______ through _______ by product I. A. reduction in levels of intermediate D; inhibition of enzyme 3 B. reduction in levels of intermediate C; inhibition of enzyme 2 C. reduction in levels of intermediate G; inhibition of enzyme 6 D. increase in levels of intermediate D; activation of enzyme 3 E. None of the above (C) 19. Products I and F have to be kept at equal molar proportions in the cell. If there is an increase in levels of product I, a positive feedback regulation of synthesis of product F would most likely occur through A. inhibition of enzyme 3 by product F. B. activation of enzyme 3 by product F. C. inhibition of enzyme 6 by product I. D. activation of enzyme 5 by product I. E. activation of enzyme 2 by product I. (D) 20. In aerobic cells, ____ in usually the immediate source of energy, used in an _____ reaction, and primarily generated in _____. A. glucose; exergonic; chloroplasts B. ATP; endergonic; mitochondria C. Acetyl-CoA; exergonic; cytoplasm D. pyruvate; endergonic; mitochondria E. None of the above (E) 21. If you are treated with a drug that causes the inner mitochondrial membrane to become permeable to small ions, what will happen and why? A. You will require more oxygen because more pyruvate is produced B. You will get hot because more entropy occurs during oxidative phosphorylation C. You will die because you cannot generate enough Acetyl CoA D. Your muscles will get sore because of the buildup of lactic acid E. None of the above (E). You will die because you cannot generate enough ATP. Mitochondria require a hydrogen gradient between their innermembrane and matrix in order to generate ATP using ATP synthase. 22. What are the reactants and products during the conversion of the 3 carbon molecule produced by glycolysis to the 2 carbon molecule required by the TCA cycle? + A. Reac
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