CELLULAR COMMUNITIES: TISSUES, STEM CELLS, AND CANCERExtracellular Matrix and Connective TissuesEpithelial Sheets and Cell JunctionsTissue Maintenance and RenewalCancerHow We Know: Making Sense of the Genes that Are Critical for CancerCHAPTER 20CELLULAR COMMUNITIES: TISSUES, STEMCELLS, AND CANCER 2009 Garland Science PublishingExtracellular Matrix and Connective Tissues20-1 Both multicellular plants and animals have _____________________.(a) cells capable of locomotion(b) cells with cell walls(c) a cytoskeleton composed of actin filaments, microtubules, and intermediate filaments(d) tissues composed of multiple different cell types20-2 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once.Plants are sedentary and thus their cells have different needs from those of cells found in motile animals. For example, in plant cells, __________________ generates the turgor pressure that drives cellgrowth. Plants have cell walls, but cell growth is possible in the developing tissue because the __________________ cell walls are expandable. The __________________ cell walls are deposited once growth has stopped, and can be specially adapted to their function. Fibers made from __________________ (the most abundant organic macromolecule on Earth) are found in plant cell walls, and provide tensile strength. In woody tissues, the __________________ in the cell walls makes the tissue more rigidand waterproof. The deposition of the cell wall is directed by the __________________ cytoskeleton.cellulose lignin secondarycollagen membranous microtubuleepidermis osmosis tertiarynuclear lamin actinpectin primary20-3 Which of the following statements about plant cell walls is tr ue?(a) The microtubule cytoskeleton directs the orientation in which cellulose is deposited in the cell wall.(b) The molecular components of the cell wall are the same in all plant tissues.(c) Because plant cell walls are rigid, they are not deposited until the cell has stopped growing.(d) The cellulose found in cell walls is produced as a precursor molecule in the cell and delivered to the extracellular space by exocytosis.20-4 Indicate the direction in which the plant cell shown in Figure Q20-4 is most likely to grow. The black lines indicate the direction of the cellulose microfibrils around the cell. Explain your answer.Figure Q20-420-5 Which of the following molecules are not found in plants?(a) cellulose(b) lignin(c) collagen(d) pectin20-6 Indicate whether the following molecules are found in plants, animals, or both.A. intermediate filamentsB. cell wallsC. microtubulesD. celluloseE. collagen20-7 Which of the following statements about animal connective tissues is true?(a) Enzymes embedded in the plasma membrane synthesize the collagen in the extracellular matrix extracellularly.(b) In connective tissue, the intermediate filaments within the cells are important for carrying the mechanical load.(c) Cells can attach to a collagen matrix by using fibronectin, an integral membrane protein.(d) Proteoglycans can resist compression in the extracellular matrix.20-8 A major distinction between the connective tissues in an animal and other main tissue types such as epithelium, nervous tissue, or muscle is _______________.(a) the ability of connective tissue cells such as fibroblasts to change shape(b) the amount of extracellular matrix in connective tissues(c) the ability of connective tissues to withstand mechanical stresses(d) the numerous connections that connective tissue cells make with each other20-9 What are the main structures providing tensile strength in the following?A. animal connective tissueB. animal epidermisC. plant cell walls20-10 Do you agree or disagree with the following statement? Explain your answer.Like many other extracellular proteins, newly synthesized collagen molecules undergo post-translational processing inside the cell to convert them into their mature form; they are then secreted and self-assemble into fibrils in the extracellular space.20-11 Fibroblasts organize the collagen of the extracellular matrix by ______________.(a) cutting and rejoining the fibrils(b) processing procollagen into collagen(c) twisting fibrils together to make ropelike fibers(d) pulling the collagen into sheets or cables after it has been secreted20-12 Match the four lettered lines in Figure Q20-12 with the appropriate numbered label.Figure Q20-121. integrin2. actin3. collagen4. fibronectin20-13 Which of the following statements about integrins is false?(a) Integrins use adaptor proteins to interact with the microtubule cytoskeleton.(b) Integrins can switch to an activated state by binding to an extracellular matrix molecule.(c) Integrins can switch to an activated state by binding to an intracellular protein.(d) An activated integrin molecule takes on an extended conformation.20-14 Proteoglycans in the extracellular matrix of animal tissues ________________.(a) chiefly provide tensile strength(b) allow cartilage to resist compression(c) are linked to microtubules through the plasma membrane(d) are polysaccharides composed of glucose subunits20-15 Which of the following statements is false?(a) Proteoglycans can act as filters to regulate which molecules pass through the extracellular medium.(b) The negative charge associated with proteoglycans attracts cations, which cause water to be sucked into the extracellular matrix.(c) Proteoglycans are a major component of compact connective tissues but are relatively unimportant in watery tissues such as the jellylike substance in the interior of the eye.(d) Glycosaminoglycans are components of proteoglycan.Epithelial Sheets and Cell Junctions20-16 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once.__________________ join the intermediate filaments in one cell tothose in the neighboring cell. __________________ anchor intermediate filaments in a cell to the extracellular matrix. __________________ involve cadherin connections between neighboring cells and are anchorage sites for actin filaments. __________________ permit the passage of small molecules from one cell to its adjacent cell. __________________ prevent the leakage of molecules between adjacent cells.adherens junctions gap junctions highway