UT Knoxville BIOL 140 - Chapter 8 (58 pages)

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Chapter 8 Cell cell interactions 2011 Pearson Education Inc Review of Plasma Membrane Structure and Function The plasma membrane is made up of a phospholipid bilayer with many interspersed proteins Proteins may be integral or peripheral The primary function of the plasma membrane is to create an environment inside the cell that is different from conditions outside The selective permeability of the membrane controls the flow of materials into and out of the cell 2011 Pearson Education Inc The Structure and Function of an Extracellular Layer Structure Most cells possess a protective layer or wall that forms just beyond the membrane This layer generally consists of a fiber composite a cross linked network of long filaments surrounded by a stiff ground substance Function The rods or filaments protect against tension and the ground substance protects against compression 2011 Pearson Education Inc 2011 Pearson Education Inc The Primary Plant Cell Wall When new plant cells form they secrete a fiber composite called a primary cell wall This wall is composed of long strands of cellulose bundled into microfibrils that form a crisscrossed network The network is filled with hydrophilic gelatinous polysaccharides such as pectin which keep the cell wall moist The primary cell wall defines the shape of the plant cell and counteracts the turgor pressure it experiences 2011 Pearson Education Inc 2011 Pearson Education Inc The Secondary Plant Cell Wall Some cells secrete a secondary cell wall inside the primary cell wall Secondary cell wall structure correlates with the specific cell s function In cells that form wood the secondary cell wall contains lignin 2011 Pearson Education Inc The Extracellular Matrix in Animals Most animal cells secrete a fiber composite called the extracellular matrix ECM Like the extracellular materials found in other organisms one of the ECM s most important functions is structural support The amount and composition of the ECM vary depending upon the cell