10) - 15:01 9/16/2010 Lysosomes: Digestive Compart'ts A...

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15:01 9/16/2010 Lysosomes: Digestive Compart’ts A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids Low pH Some types of cell can engulf another cell by phagocytosis; this forms a food vacuole A lysosome fuses with the food vacuole and digests the molecules Lysosomes also use enzymes to recycle the cell’s own organelles and macromolecules, a process called autophagy Vacuoles A plant cell or fungal cell may have one or several vacuoles Food vacuoles are formed by phagocytosis Central vacuoles , found in many mature plant cells, hold organic compounds and water Tonoplast is the membrane that surrounds the vacuole Mature plant-done growing, which grows by vacuole (osmotic pressure) The Endomembrane System The endomembrane system is a complex and dynamic player in the cell’s compart’tal organization The cytoskeleton is a network of fibers that organizes structures and activities in the cell The cytoskeleton is a network of protein fibers extending thru out the cytoplasm It organizes the cell’s structures and activities anchoring many organelles It is composed of three types of molecular structures:
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Microtubules Microfilaments Intermediate filaments Roles of the Cytoskeleton: Support, Motility, and Regulation The cytoskeleton helps to support the cell and maintain its shape It interacts w/ motor proteins to produce motility Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton Components of the Cytoskeleton Three main types of fibers make up the cytoskeleton Microtubules are the thickest of the three components of the cytoskeleton (made of tubulin Microfilaments, also called actin filaments, are the thinnest components Intermediate filaments are fibers with diameters in a middle range Microtubule fxn: maintenance of cell shape, cell motility, chromosome move’ts in cell division, and organelle move’ts Microfilaments (actin filaments – two intertwined strands) fxn: Maintenance of cell shape, changes in cell shape, muscle contraction, cytoplasmic streaming, cell motility, and cell division Intermediate Filaments (fibrous keratin proteins supercoiled into thicker cables) fxn: maintenance of cell shape, anchorage of nucleus and certain other organelles, formation of nuclear lamina Extracellular components and connections Most cells synthesize and secrete materials that are external to the plasma membrane These extracellular structures include: Cell walls of plants The extracellular matrix (ECM) of animal cells Intercellular junctions
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Cell Walls of Plants (Fig 6-28) The cell wall is an extracellular structure that distinguishes plant cells from animal cells Prokaryotes, fungi, and some protists also have cell walls The cell wall protects the plant cell, maintain its shape Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein
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10) - 15:01 9/16/2010 Lysosomes: Digestive Compart'ts A...

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