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of specialized cell projections, such as cilia and flagella. c.Organelles – are specialized structures within the cell that have characteristic shapes, and they perform specific functions in cellular growth, maintenance and production. i.each type of organelle has its own set of enzymes that carry out specific reactions, and serves as a functional compartment for specific bio chemical process. ii.Maintain homeostasis. d.Centrosome – consists of two components: a pair of centrioles and pericentriolar material.
i.The two centrioles are cylindrical structures, each composed of nine clusters of three microtubules arranges in a circular pattern. The long axis of one centriole is at a right angle to the long axis on the other. ii.Surrounding the centrioles is pericentriolar material which contains hundreds of right-shapes complexes composed of the protein tubulin. These tubulin complexes are the organizing centers for growth of the mitotic spindle, which plays a critical role in cell division, and for microtubule formation in nondividing cells. iii.During cell division, centrosomes replicate so that succeeding generations of cells have the capacity for cell division. Fx: 1. The pericentriolar material of the centrosome contains tubulins that build microtubules in nondividing cells. 2. . The pericentriolar material of the centrosome forms the mitotic spindle during cell division. e.Cilia and flagella – microtubules are the dominant components of cilia and flagella, which are motile projections of the cell surface. i.Cilia- move fluids along a cell’s surface – are numerous, short, hair-like projections that extend from the surface of the cell. Oarlike pattern of beating, it is relatively stiff during the power stoke (oar digging into the water) but more flexible during the recovery stroke (oar moving above the water preparing for a new stroke).The coordinated movement of many cilia on the surface of a cell causes the steady movement of fluid along the cells surface. ii.Flagella – a flagellum moves an entire cell – are similar in structure but are typically much longer.Generates motion along its axis by rapidly wiggling in a wavelike pattern. Ex: sperm tailf.Ribosomes– sites of protein synthesis. Fx: 1. Associated with endoplasmic reticulum synthesize proteins destined for insertion in the plasma membrane or secretion from the cell. 2. Free ribosomes synthesize proteins used in the cytosol. g.Endoplasmic reticulum– a network of membranes in the form of flattened sacs or tubules. i.The ER extends from the nuclear envelope (membrane around the nucleus), to which it is connected and projects through the cytoplasm. ii.The ER is so extensive that it constitutes more than half of the membranous surfaces within the cytoplasm of most cells. Two types:Rough ER– synthesizes glycoproteins and phospholipids that are transferred into cellularorganelles, inserted into the plasma membrane, or secreted during exocytosis. -Continuous with the nuclear membrane and usually is folded into a series of flattened sacs. -The outer surfaces is studded with ribosomes, the sites of protein synthesis.