Chapter 8 Cell Cell Interactions How do cells work together and communicate The Cell Membrane The fluid mosaic model of membrane structure suggests that some proteins are inserted into the lipid bilayer making the membrane a fluid dynamic mosaic of phospholipids and proteins The Cell Surface 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 and the ground substance protects against The Cell Wall in Plants When new plant cells form they secrete a fiber composite called a primary cell wall This wall is composed of long strands of 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 Extracellular Matrix in Animals Most animal cells secrete a fiber composite called the The ECM consists of a ground substance formed of gelatinous polysaccharide and a network of protein fibers The most common ECM protein fiber is collagen which is more elastic than cellulose and forms a flexible extracellular layer In addition to structural support the ECM also helps The Extracellular Matrix Connects to the Cytoskeleton The ECM is strengthened by connections to Actin protein filaments in the cytoskeleton bind to transmembrane integrin proteins Integrins bind to ECM proteins such as fibronectins which then bind to collagen Direct linkage between the cytoskeleton and ECM ECM varies due to tissue type Different tissues will have different amounts of extracellular matrix The difference sue to location and functions of the cell in an organism Define these terms and put in order Multicellularity Organs Tissue 1 Cell Attachments 1 Cell Attachments Tight Junctions 1 Cell Attachments Tight Junctions Tight junctions are composed of specialized proteins in the plasma membranes of adjacent animal cells These proteins line up and bind to each other stitching the two cells together to form a between the two plasma membranes Tight junctions are usually found between cells in tissues that form a barrier such as the tissue lining the stomach or bladder Tight junctions are dynamic and variable 1 Cell Attachments Desmosomes Desmosomes Desmosomes are made of proteins that link Desmosomes are common in epithelial and muscle tissue These proteins bind to each other and to the proteins that anchor cytoskeletal intermediate filaments How Do Adjacent Cells Communicate 2 Adjacent Cell Communication Plasmodesmata Plant cells are connected by plasmodesmata gaps in the cell wall where the plasma membranes cytoplasm and smooth ER of two cells connect 2 Adjacent Cell Communication Gap Junctions In most animal tissues gap junctions connect adjacent cells by forming channels that allow the flow of water ions amino acids sugars and nucleotides between cells Cell Adhesion and Communication How Do Distant Cells Communicate 3 Distant Cell Communication 3 Distant Cell Communication
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