Cell Biology Exam 2 (Essential Cell Biology, 3rd Edition, by Alberts)

Introduction to Cell Biology Name: October 28, 2010 Student ID: Exam II - Version 1 Section 1: Complete each sentence with one of the two answers (A / B) (3 points each). 1. donate high-energy electrons for synthesis of ATP. A) NAD+ B) NADH 2. Modern eucaryotes depend on mitochondria to generate most of the cell’s ATP. A single molecule of glucose can generate molecules of ATP. A) 30 B) 36 3. gradient serves as an energy store and is used to drive the synthesis of ATP by the ATP synthase. A) Sodium B) Proton 4. The chemiosmotic mechanism of ATP synthesis in mitochondria is called . A) oxidative phosphorylation B) electron transfer 5. The cytochrome oxidase is a protein complex that receive electron from . A) cytochrome b-c1 complex B) cytochrome c 6. Nuclear proteins for their nuclear import through nuclear pore complexes. A) need to be unfolded B) do not need to be unfolded 7. receives proteins and lipids from the ER, modifies them, and then and dispatched them to other destinations in the cells. A) Golgi apparatus B) Endosomes 8. Nuclear localization signal is the signal sequence that directs a protein from the cytosol into the nucleus and typically consists of a short amino acid sequence as shown in . A) -Proline-Proline-Lysine-Lysine-Lysine-Arginine-Lysine-Valine- B) -Serine-Lysine-Leucine- 9. Vesicular transport between membrane-enclosed compartments of endomembrane system is highly organized. The endomembrane system includes nuclear, ER, Golgi apparatus, endosomes and . A) lysosomes B) mitochondria 1 (Version 1) Introduction to Cell Biology Name: October 28, 2010 Student ID: 10. The supplies the plasma membrane with newly synthesized lipids and proteins. A) constitutive secretory pathway B) regulated exocytosis pathway 11. singals can act over a long range. A) Endocrine B) Paracrine 12. Steroid hormones, which can diffuse directly across the plasma membrane, are all . A) hydrophobic B) hydrophilic 13. GPCRs activate a class of G proteins that can transmit signal and then switch themselves off by hydrolyzing their bound GTP to GDP. A) monomeric B) trimeric 14. PKA, PKC, and CaM-kinases phosphorylate selected target proteins on , thereby altering protein activity. A) serines and threonines B) tyrosines 15. Ras activate a MAP-kinase signaling module by first activating . A) MAP kinase B) MAP kinase kinase kinase 16. The end of a double stranded DNA is characterized by a phosphate group. A) 5' B) 3' 17. A nucleosome contains molecule(s) each of histones H2A, H2B, H3 and H4. A) one B) two 18. Hershey and Chase showed that genes are made of DNA. The DNA in one batch of viruses is radioactively labeled with . A) 35S B) 32P 19. Each human chromosome has origin(s) of replication, one centromere, and two telomeres. A) multiple B) one 2 (Version 1) Introduction to Cell Biology Name: October 28, 2010 Student ID: 20. Heterochromatin and euchromatin each represent a set of different chromatin structure with different degrees of extension or condensation. Overall, heterochromatin is condensed than euchromatin. A) more B) less Section 2: Multiple Choice. Identify the single BEST answer for each question (3 points each). 21. 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. 22. Which component of the electron-transport chain is required to combine the pair of electrons with molecular oxygen? A) cytochrome c B) cytochrome b-c1 complex C) ubiquinone D) cytochrome c oxidase 23. Which of the following types of ion movement might be expected to require co-transport of protons from the intermembrane space to the matrix, inasmuch as it could not be driven by the membrane potential across the inner membrane? (Assume that each ion being moved is moving against its concentration gradient.) A) import of Ca2+ into the matrix from the intermembrane space B) import of acetate ions (CH3COO?) into the matrix from the intermembrane space C) exchange of Fe2+ in the matrix for Fe3+ in the intermembrane space D) exchange of ATP from the matrix for ADP in the intermembrane space 24. NADH and FADH2 carry high-energy electrons that are used to power the production of ATP in the mitochondria. These cofactors are generated during glycolysis, the citric acid cycle, and the fatty acid oxidation cycle. Which molecuale below can produce the most ATP? Explain your answer. A) NADH from glycolysis B) FADH2 from the fatty acid cycle C) NADH from the citric acid cycle D) FADH2 from the citric acid cycle 3 (Version 1) Introduction to Cell Biology Name: October 28, 2010 Student ID: 25. Experimental evidence supporting the chemiosmotic hypothesis was gathered by using artificial vesicles containing a protein that can pump protons in one direction across the vesicle membrane to create a proton gradient. Which protein was used to generate the gradient in a highly controlled manner in response to light? A) cytochrome c oxidase B) NADH dehydrogenase C) cytochrome c D) bacteriorhodopsin 26. Which of the following is not an electron carrier that participates in the electron-transport chain? A) cytochrome B) quinone C) rhodopsin D) copper ion 27. Oxidative phosphorylation, as it occurs in modern eucaryotes, is a complex process that probably arose in simple stages in primitive bacteria. Which mechanism is proposed to have arisen first as this complex system evolved? A) electron transfers coupled to a proton pump B) the reaction of oxygen with an ancestor of cytochrome oxidase C) ATP-driven proton pumps D) the generation of ATP from the energy of a proton gradient 28. The drug dinitrophenol (DNP) makes the inner mitochondrial membrane permeable to H+ ions. Therefore, when added to mitochondria, DNP A) will decrease the production of ATP. B) will decrease the pH gradient across the membrane. C) will cause electron pump activity to stop. D) will decrease both the production of ATP and the pH gradient across the membrane. 29. Bongkrekic acid is an antibiotic that inhibits the ATP/ADP transport protein in the inner mitochondrial membrane. Which of the following will allow electron transport to occur in mitochondria treated with bongkrekic acid? A) placing the mitochondria in anaerobic conditions B) adding FADH2 C) making the inner membrane permeable to protons D) inhibiting the ATP synthase 30. Which of the following statements about the endoplasmic reticulum (ER) is false? A) The ER is the major site for new membrane synthesis in the cell. B) Proteins to be delivered to the ER lumen are synthesized on smooth ER. C) Steroid hormones are synthesized on the smooth ER. D) The ER membrane is contiguous with the outer nuclear membrane. 31. Where are proteins in the mitochondria synthesized? A) in the cytosol B) in the mitochondria C) on the endoplasmic reticulum D) in both the cytosol and the mitochondria 4 (Version 1) Introduction to Cell Biology Name: October 28, 2010 Student ID: 32. Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? A) Nuclear transport receptors would be unable to bind cargo. B) Nuclear transport receptors would be unable to enter the nucleus. C) Nuclear transport receptors would be unable to release their cargo in the nucleus. D) Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils. 33. You are interested in Fuzzy, a soluble protein that functions within the ER lumen. Given that information, which of the following statement must be true? A) Fuzzy has a C-terminal signal sequence that binds to SRP. B) Only one ribosome can be bound to the mRNA encoding Fuzzy during translation. C) Fuzzy must contain a hydrophobic stop-transfer sequence. D) Once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded. 34. The following figure shows the organization of a protein that normally resides in the plasma membrane. The boxes labeled 1 and 2 represent membrane-spanning sequences and the arrow represents a site of action of signal peptidase. Given this diagram, which of the following statements must be true? A) The N-terminus of this protein is cytoplasmic. B) The C-terminus of this protein is cytoplasmic. C) The mature version of this protein will span the membrane twice, with both the N and C- termini in the cytoplasm. D) None of the above. 35. Which of the following choices reflects the appropriate order through which a protein destined for the plasma membrane travels? A) lysosome ? endosome ? plasma membrane B) ER ? lysosome ? plasma membrane C) Golgi ? lysosome ? plasma membrane D) ER ? Golgi ? plasma membrane 5 (Version 1) Introduction to Cell Biology Name: October 28, 2010 Student ID: 36. Which of the following statements about vesicle budding from the Golgi is false? A) Clathrin molecules are important for binding to and selecting cargos for transport. B) Adaptins interact with clathrin. C) After vesicle budding is complete, clathrin molecules are released from the vesicle. D) Clathrin molecules act at the cytosolic surface of the Golgi membrane. 37. Your friend has just joined a lab that studies vesicle budding from the Golgi and has been given a cell line that does not form mature vesicles. He wants to start designing some experiments but wasn’t listening carefully when he was told about the molecular defect of this cell line. He’s too embarrassed to ask and comes to you for help. He does recall that this cell line forms coated pits but vesicle budding and the removal of coat proteins don’t happen. Which of the following proteins might be lacking in this cell line? A) clathrin B) Rab C) dynamin D) adaptin 38. Which of the following statements about the unfolded protein response (UPR) is false? A) Activation of the UPR results in the production of more ER membrane. B) Activation of the UPR results in the production of more chaperone proteins. C) Activation of the UPR occurs when receptors in the cytoplasm sense misfolded proteins. D) Activation of the UPR results in the cytoplasmic activation of transcription regulator. 39. All members of the steroid hormone receptor family . A) are cell-surface receptors B) do not undergo conformational changes C) are found only in the cytoplasm D) interact with signal molecules that diffuse through the plasma membrane 40. Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following statements is false? A) Heart muscle cells decrease their rate and force of contraction when they receive acetylcholine, whereas skeletal muscle cells contract. B) Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family. C) Active acetylcholine receptors on salivary gland cells and heart muscle cells activate different intracellular signaling pathways. D) Heart muscle cells, salivary gland cells, and skeletal muscle cells all respond to acetylcholine within minutes of receiving the signal. 6 (Version 1) Introduction to Cell Biology Name: October 28, 2010 Student ID: 41. The following figure shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood-vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? A) a smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO B) a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP C) a muscle cell that has cyclic GMP phosphodiesterase constitutively active D) a drug that blocks an enzyme involved in the metabolic pathway from arginine to NO 42. Acetylcholine binds to a GPCR on heart muscle, making the heart beat more slowly. The activated receptor stimulates a G protein, which opens a K+ channel in the plasma membrane, as shown in the following figure. Which of the following would enhance this effect of the acetylcholine? A) addition of a high concentration of a non-hydrolyzable analog of GTP B) addition of a drug that prevents the ? subunit from exchanging GDP for GTP C) mutations in the acetylcholine receptor that weaken the interaction between the receptor and acetylcholine D) mutations in the acetylcholine receptor that weaken the interaction between the receptor and the G protein 7 (Version 1) Introduction to Cell Biology Name: October 28, 2010 Student ID: 43. What produces diacylgycerol and IP3? A) PKA B) Phospholipase C C) PKC D) PKB 44. Which of the following accurately describes a receptor tyrosine kinase? A) It can lead to the activation of Ras. B) It is a multi-pass transmembrane receptor. C) It is phosphorylated on its threonine residues. D) It can activate IP3. 45. The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? A) a mutation that prevents dimerization of the receptor B) a mutation that destroys the kinase activity of the receptor C) a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor D) a mutation that prevents the binding of the normal extracellular signal to the receptor 46. Which of the following statements is true? A) MAP kinase is important for phosphorylating MAP kinase kinase. B) PI 3-kinase phosphorylates a lipid in the plasma membrane. C) Ras becomes activated when an RTK phosphorylates its bound GDP to create GTP. D) STAT proteins phosphorylate JAK proteins, which then enter the nucleus and activate gene transcription. 47. Akt promotes the survival of many cells. It is activated by an intracellular signaling pathway that is triggered by an RTK that activates PI 3-kinase, as diagrammed in the following figure. Which of the following statements is false? A) In the presence of a survival signal, Akt localizes to the plasma membrane by binding to phosphorylated inositol phospholipid. B) In the absence of survival signal, Bad inhibits the cell death inhibitor protein Bcl2. C) In the presence of survival signal, the cell death inhibitory protein Bcl2 is active. D) In the absence of survival signal, Bad is phosphorylated. 8 (Version 1) Introduction to Cell Biology Name: October 28, 2010 Student ID: 48. In human females, A) inactivation of an X-chromosome leads to the expression of primarily a mother's X chromosome associated genes. B) cell will inactivate either one of its X-chromosomes with a 50/50 chance after each round of replication during the whole life of a human female. C) all cells have the same X chromosome inactivated. D) inactivation of an X-chromosome leads to a 50/50 chance that a father's or mother's X- associated gene will be expressed in at least part of every tissue. 49. In a DNA double helix, . A) the two DNA strands are identical B) purines pair with purines C) thymine pairs with cytosine D) the two DNA strands run antiparallel 50. The human genome has enough DNA to stretch more than 2 m. However, this DNA is not contained in a single molecule; it is divided into linear segments and packaged into structures called chromosomes. What is the total number of chromosomes found in each of the somatic cells in your body? A) 22 B) 23 C) 44 D) 46 Section 3: Extra Credit (3 points) 51. Stepwise condensation of linear DNA happens in five different packing processes. Which of the following four processes has a direct requirement for histone H1? A) formation of “beads-on-a-string” B) formation of the 30 nm fiber C) looping of the 30 nm fiber D) packing of loops to form interphase chromosomes 9 (Version 1) Introduction to Cell Biology Name: October 28, 2010 Student ID: Answers 1. B. 2. A. 3. B. 4. A. 5. B. 6. B. 7. A. 8. A. 9. A. 10. A. 11. A. 12. A. 13. B. 14. A. 15. B. 16. A. 17. B. 18. B. 19. A. 20. A. 21. C. 22. D. 23. B. 24. C. 25. D. 26. C. 27. C. 28. D. 29. C. 30. B. 31. D. 32. C. 33. D. 34. B. 35. D. 36. A. 37. C. 38. C. 39. D. 40. B. 41. B. 42. A. 43. B. 44. A. 45. C. 46. B. 47. D. 48. D. 49. D. 50. D. 51. B.  10 (Version 1)