Lodish 8e Ch20 Test Bank PDF

20 Integrating Cells into Tissues Section 20.1 1. The functions of the extracellular matrix include: a. supporting differentiation. b. inducing morphogenesis. c. binding growth hormones. d. all of the above Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Modera...

20 Integrating Cells into Tissues Section 20.1 1. The functions of the extracellular matrix include: a. supporting differentiation. b. inducing morphogenesis. c. binding growth hormones. d. all of the above Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 2. The major families of cell surface adhesion molecules include: a. cadherins and selectins. b. integrins. c. the Ig-superfamily. d. all of the above Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 3. In a classic experiment, H. V. Wilson studied aggregation of mechanically dissociated individual sponge cells from two different species. He found that the cells of each species would adhere to one another but not to cells of the other species. Describe the factors involved in this species-specific aggregation. Ans: The sponge cells aggregate as a result of calcium-dependent species-specific interactions that involve homotypic proteoglycan aggregation factors in the extracellular matrix that bind to cells via surface receptors. Question Type: Essay Chapter: 20 Blooms: Applying Difficulty: Moderate 4. Cadherin cellular adhesion molecules promote: a. collagen binding. b. multiadhesive matrix protein binding. c. cell-specific homophilic interactions. d. all of the above Ans: c Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Easy Section 20.2 5. Desmosomes: a. associate with actin filaments on the cytoplasmic side. b. contain the transmembrane proteins desmoglein and desmocollin. c. inhibit transfer of membrane proteins from the basolateral to the apical domain. d. contain integrins. Ans: b Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 6. Which of the following statements best describes the difference between low-affinity integrins and high-affinity integrins? a. Many integrins can exist in two conformations: a low-affinity (bent) conformation and a high-affinity (straight) conformation. b. Dissociation of the heterodimer converts many integrins from the low-affinity to the high-affinity state. c. Association of the heterodimer converts many integrins from the low-affinity to the high-affinity state. d. Proteolytic cleavage of the C-terminal tails of the two subunits converts many integrins from the low-affinity to the high-affinity state. Ans: a Question Type: Multiple choice Chapter: 20 Blooms: Applying Difficulty: Moderate 7. Vertebrate gap junctions are composed of: a. adherins. b. collagens. c. connexins. d. integrins. Ans: c Question Type: Multiple choice Chapter: 20 Blooms: Remembering Difficulty: Easy 8. A tight junction is made up of which of the following proteins? a. tricellulin b. occludin c. claudin d. all of the above Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Remembering Difficulty: Moderate 9. EDTA is a divalent cation chelator. Propose an explanation for how EDTA promotes the dissociation of animal cell tissue? 2+ Ans: Much of cell-cell adhesion is mediated by cadherins. Cadherin interactions between cells are Ca dependent. EDTA 2+ chelates divalent cations, including Ca , leading to dissociation of cadherin cell-cell interactions. Question Type: Essay Chapter: 20 Blooms: Applying Difficulty: Moderate 10. What is the function of a gap junction? Ans: Gap junctions are communicating junctions between cells that allow for the ready exchange of small molecules up to about 2000 daltons. Gap junctions are composed of connexin protein molecules, which interact between adjacent cells to form small amino acid–lined pores between the cells. Question Type: Essay Chapter: 20 Blooms: Understanding Difficulty: Moderate 11. What are the cytoskeletal proteins associated with hemidesmosomes? Ans: Hemidesmosomes are macromolecular complexes that are linked to intermediate filaments composed of keratin. Question Type: Essay Chapter: 20 Blooms: Understanding Difficulty: Easy 12. What is a polarized epithelial cell? Ans: A polarized epithelial cell is one whose membrane is differentiated into two domains, the apical domain and the basolateral domain. These characteristics can be maintained even in tissue culture. For example, Madin-Darby canine kidney cells in culture demonstrate microvilli on their apical surfaces and tight junctions and desmosomes that separate the apical and basolateral domains. Question Type: Essay Chapter: 20 Blooms: Understanding Difficulty: Moderate 13. Cellular responses to adhesion receptor signaling do NOT include: a. cell proliferation. b. cytoskeletal organization. c. gene transcription. d. all of the above Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Easy Section 20.3 14. Which of the following is the term used to describe a thin, sheet-like meshwork of extracellular matrix components that can be found in epithelial cells? a. basal lamina b. basement membrane c. gap junction d. cell wall Ans: a Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Easy 15. Basal lamina include all of the following, except: a. type I collagen. b. type IV collagen. c. laminin. d. nidogen. Ans: a Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Easy 16. Which one of the following is NOT a property of perlecan? a. It contains laminin-like LG domains. b. It is a proteoglycan. c. It is only found in the basal lamina. d. It is a glycoprotein. Ans: c Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Easy 17. Multiadhesive matrix proteins form adhesive bridges between what components or structures? Ans: Multiadhesive matrix proteins link cell-surface components such as integrins and ECM, extracellular matrix components such as collagen, and the glycosaminoglycan (GAG) portion of proteoglycans. Both laminin and fibronectin interact with integrins, collagen, and proteoglycan GAGs. Question Type: Essay Chapter: 20 Blooms: Understanding Difficulty: Moderate Section 20.4 18. The collagen triple-helix domain is NOT: a. rich in glycine. b. an helix. c. rich in proline. d. rich in hydroxyproline. Ans: b Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 19. Proteoglycans are: a. located exclusively at the cell surface. b. located exclusively in the extracellular matrix. c. highly positively charged. d. glycoproteins that contain glycosaminoglycans. Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 20. Syndecans are cell-surface proteoglycans that: a. bind to collagens. b. bind to multi-adhesive matrix proteins. c. anchor cells to the extracellular matrix. d. all of the above Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 21. Biological roles of proteoglycans and hyaluronan include all of the following, except: a. maintenance of porosity for the diffusion of small molecules between cells and tissues. b. presentation of growth factors to cells. c. resistance to compression. d. storage sites for extracellular energy reserves. Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 22. Which extracellular matrix component is expressed in a cell-specific manner and binds to the tripeptide sequence Arg-Gly- Asp? a. integrins b. collagen c. proteoglycans d. fibronectins Ans: a Question Type: Multiple choice Chapter: 20 Blooms: Remembering Difficulty: Easy 23. Polymerization of collagen into large collagen fibers occurs: a. in the endoplasmic reticulum. b. in the Golgi complex. c. in secretory vesicles. d. extracellularly. Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 24. Hydroxyproline is important in the formation of staple collagen polymers within cells. The formation of hydroxyproline requires: a. vitamin A. b. vitamin B. c. vitamin C. d. vitamin D. Ans: c Question Type: Multiple choice Chapter: 20 Blooms: Remembering Difficulty: Easy 25. Which of the following is NOT true regarding matrix metalloproteases? a. Their activity depends on zinc ions. b. They are responsible for cleaving -catenin from E-cadherin. c. They are inhibited by TIMPs. d. Some of the members are called gelatinases. Ans: b Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 26. How are multiple forms of fibronectin generated? Ans: Multiple molecular forms of fibronectin are generated by differentially splicing the precursor RNA products derived from one gene. Question Type: Essay Chapter: 20 Blooms: Understanding Difficulty: Moderate 27. What are the three unusually abundant amino acids in collagen? Ans: The three unusually abundant amino acids in collagen are glycine, proline, and hydroxyproline. Note that hydroxyproline is the hydroxylated form of proline and is not one of the standard 20 amino acids. Question Type: Essay Chapter: 20 Blooms: Remembering Difficulty: Moderate 28. In mice engineered to overexpress the syndecan-1 gene in the hypothalamic region of the brain and other tissues, normal control of feeding by antisatiety peptides is disrupted, and the animals overeat and become obese. Other studies have shown that syndecan-3 may also be involved in the regulation of feeding behavior. Given the following information, which of these outcomes might you expect in experimentally manipulated mice? Hypothalmic expression of syndecan-3 is increased by fasting. Syndecan-3 knockout mice are resistant to diet-induced obesity. Heparinase can cleave syndecan-3 to release heparin sulfate GAG chains that may suppress the activity of antisatiety peptides and feeding behavior. A. Overexpression of heparinase in mice with normal levels of syndecan-3 would result in resistance to diet-induced obesity. B. In mice with normal levels of syndecan-3, fasting followed by free access to a high-fat diet would lead to resistance to diet- induced obesity. C. Lack of heparinase in mice with normal levels of syndecan-3 would result in animals that overeat and become obese. D. Overexpression of heparinase in syndecan-3 knockout mice would reverse the resistance to diet-induced obesity. E. There are two plausible hypotheses: 1) Overexpression of heparinase in mice with normal levels of syndecan-3 would result in resistance to diet-induced obesity; and 2) lack of heparinase in mice with normal levels of syndecan-3 would result in animals that overeat and become obese. Ans: E Question Type: Essay Chapter: 20 Blooms: Evaluating Difficulty: Difficult 29. What kinds of polymerized structures do collagen types form? Ans: Collagens form three types of polymerized structures: fibrillar collagens, fibril-associated collagens, and sheet-forming collagens. Question Type: Essay Chapter: 20 Blooms: Remembering Difficulty: Moderate 30. Heparan sulfate, an example of a(n) _____________, aids in the activation of ____________. a. GAG; FGFR b. proteoglycan; FGF c. multi-adhesive protein; FGFR d. integrin; cell motility Ans: a Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Easy Section 20.5 31. NCAMs, a group of cell-adhesion proteins belonging to the Ig superfamily: a. are more heavily sialylated in embryonic tissues than in adult tissues. b. bind to proteoglycans. 2+ c. mediate Ca -dependent cell-to-cell binding. d. all of the above Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 32. Dystroglycan is a large glycoprotein that binds to dystrophin in muscle cells. It is also present in other cells and can also bind to: a. laminin. b. the virus that causes Lassa fever. c. the bacterium that causes leprosy. d. all of the above Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 2+ 33. What is the role of Ca in NCAM-mediated homophilic cell-cell adhesion? 2+ 2+ Ans: Ca has no role in NCAM-mediated cell-cell adhesion. NCAMs are not Ca -dependent. Question Type: Essay Chapter: 20 Blooms: Remembering Difficulty: Easy 34. What is the oligomeric structure of integrins? Ans: Integrins are heterodimers composed of and subunits. There are three different known subunits and approximately 13 different known subunits. Hence, much of the difference in integrins is attributed to differences in the subunit. Question Type: Essay Chapter: 20 Blooms: Understanding Difficulty: Moderate 35. Describe the importance of extravasation and how leukocytes use this mechanism to fight infection/inflammation. Ans: In response to signals in the areas of inflammation and infection, endothelial cells move vesicle-sequestered selectins to the cell surface where they mediate weak binding to circulating leukocytes. Leukocytes roll along the endothelial surface, where they encounter platelet-activating factor (PAF) and ICAM-1, which also appeared in response to inflammatory signals. PAF, other secreted activators, and chemokines induce morphological changes in the leukocyte, as well as activation of L 2 integrins on the surface. Integrin binding to CAMs on the endothelium holds the leukocyte, thereby allowing it to alter its shape and then move (or transmigrate) between endothelial cells to the site of inflammation and/or infection in the underlying tissue. Question Type: Essay Chapter: 20 Blooms: Applying Difficulty: Moderate 36. Which of the following best describes the structure of integrins? a. Integrins cluster in cis until coming into contact with another cell, where a trans network forms. b. Integrins are homodimers of subunits expressed in a cell-type specific manner, c. A single integrin subunit forms heterophilic interactions with fibronectin and laminin. d. Integrins are heterodimers composed of and subunits. Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 37. What signal is released by endothelial cells to recruit circulating leukocytes? a. Vesicle-sequestered P-selectins are moved to the cell surface. b. Vesicle-sequestered αLβ2 molecules are moved to the cell surface. c. Integrins are cleaved from the plasma membrane so that the extracellular domain can bind leukocytes. d. Secreted glycoproteins trigger leukocytes to initiate “rolling” motility. Ans: a Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 38. People with a defect in the synthesis of the integrin β2 subunit exhibit reduced: a. leukocyte attachment. b. leukocyte rolling. c. endothelial cell activation. d. extravasation. Ans: d Question Type: Multiple choice Chapter: 20 Blooms: Applying Difficulty: Moderate 39. What effect might an injection of RGD peptide have on tumor cells moving through the blood/lymph system? a. block cell attachment to new tissue and therefore prevent metastasis b. encourage clumping of cancer cells for removal by the immune system c. promote tumor cell binding to platelets and potentially lead to a fatal clot d. block integrin-mediated cell cycle progression Ans: a Question Type: Multiple choice Chapter: 20 Blooms: Applying Difficulty: Moderate 40. As fibroblasts form a three-dimensional structure in contact with the ECM, the cells bound to ECM: a. exhibit less mobility. b. make the same adhesion structures as fibroblasts grown in two-dimensional culture. c. proliferate at a faster rate. d. de-differentiate. Ans: c Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Easy Section 20.6 41. Pectins and hyaluronic acid are both: a. secreted by animal cells. b. very negatively charged. c. proteins. d. intracellular substances. Ans: b Question Type: Multiple choice Chapter: 20 Blooms: Understanding Difficulty: Moderate 42. Which of these is NOT a component of plant cell walls? a. collagen b. pectin c. cellulose d. hemicellulose Ans: a Question Type: Multiple choice Chapter: 20 Blooms: Remembering Difficulty: Easy 43. How are cellulose fibrils laid down in parallel arrays? Ans: Cellulose fibrils are synthesized by the cell-surface enzyme cellulose synthase. Cellulose synthase movement is guided by underlying parallel arrays of microtubules. Question Type: Essay Chapter: 20 Blooms: Applying Difficulty: Easy 44. What is the function of plasmodesmata in plants? Ans: The function of plasmodesmata is to connect plant cells. They form the functional equivalent of gap junctions between plant cells. However, as cytoplasmic continuities between cells, larger molecules including various proteins can be exchanged between cells. Question Type: Essay Chapter: 20 Blooms: Understanding Difficulty: Easy