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Transcript
Plant Cell Walls Chapter 3 Where is the cell wall of plant cells located? A. Inside the plasma membrane B. Outside the plasma membrane C. Between the plasma membranes of two adjacent cells The Eukaryotic Plant Cell • cell wall • plasma membrane • cytoplasm • various organelles • cytoplasmic streaming • nucleus • vacuole bound by tonoplast Cell Wall Functions • constrains protoplast expansion • gives turgidity to plant • determines size/shape of cell • cells classified largely based upon cell wall traits • contain enzymes, absorb, transport and secrete substances • play important role in defense • NOT JUST A CONTAINER BOUNDARY Primary Cell Walls • outside of the plasma membrane • deposited while cell grows • contain thin areas • primary pit fields • plasmodesmata connect cell-tocell • (cytoplasmic connections) • shared with adjacent cell • middle lamella • joins primary cell walls of adjacent cells Plasmodesmata Chemistry of Primary Cell Walls • cellulose • glucose monomers • bundled into microfibrils • wound and coiled into macrofibrils • hemicelluloses • polysaccharides that limit cell wall extensibility • pectins • • • • • • primary cell walls and middle lamella • give wall pliability; act as cement glycoproteins lignins cutin suberin waxes Cell growth determined by cellulose microfibril orientation Secondary Cell Walls • formed inside the primary wall • different staining qualities than primary cell wall • very thick • not present in all cells • formed after cell growth • function in strength and water transport • abundant cellulose and hemicellulose • pectins and glycoproteins absent - thus not elastic • lignins common - gives hardness and rigidity Secondary Cell Wall Examples • Vascular Tissue • xylem • vessel elements • tracheids (gymnosperms) • schlerenchyma fibers • phloem • schlerenchyma fibers Pine stem • Ground Tissue • schlerenchyma fibers dicot stem dicot stem Basswood stem (angiosperm stem) monocot stem The primary cell wall of plant cells is located inside the plasma membrane. True False The secondary cell wall is located inside the plasma membrane. True False
