CTYOSKELETON provides the cell with an internal framework elaborate series of protein rods thru out cytosol o microtubules dynamic hollow tubes most radiate from centrosome determine overall shape of cell and distribution of organelles o microfilaments dynamic actin strands attached to cytoplasmic side of plasma membrane involved in cell motility change in shape endocytosis and exocytosis o intermediate filaments tough insoluble ropelike protein fibers resist pulling forces on the cell and attach to desmosomes CELLULAR PROJECTIONS not found in all cells microvilli contain actin used for movement o finger like projections that increase surface area for absorption o cilia move materials across the cell surface located in the respiratory system to move mucus o flagella propel the cell the only flagellated cell in the human body is sperm o anchoring junctions that prevent cells from being pulled apart agst MEMBRANE JUNCTIONS tight junctions o impermeable junctions o bind cells together into leakproof sheets desmosomes mechanical stress gap junctions o allow communication bw cells o composed of connexon MEMBRANE TRANSPORT two major classes o PASSIVE processes No cellular E ATP required Substance moves down the concentration gradient Potential E is converted to Kinetic E as the driving force Simple diffusion facilitated diffusion channel and carrier and osmosis o ACTIVE processes Energy required directly indirectly Occurs only in living cell membranes o Active transport by solute pumping primary vs secondary o Vesicular transport exocytosis endocytosis phagocytosis and pinocytosis transcytosis TONICITY Isotonic solution w same solute concentration as that of the cytosol Ability of a solution to cause a cell to shrink or swell Hypertonic solution having greater solute concentration than that of cytosol Hypotonic solution having lesser solute concentration than that of cytosol WHY is understanding tonicity important IV Ringer s Solution Lactated Ringer s solution is a solution that is isotonic with blood and intended for intravenous administration giving liquid substances thru the veins Developmental aspects of cells and aging Chemical signals in the embryo channel cells into specific developmental pathways by turning some genes off Development of specifc and distinctive features inc ells is called cell differentiation Elimination of excess injured or aged cells occurs thru programmed rapid cell death apoptosis followed by phagocytosis Most cells of the body contain the same DNA but are not identical Theories of cell aging o Wear and tear theory little chemical insults and free radicals have cumulative effects over time leading to aging o Immune system disorders autoimmune responses and progressive weakening of the immune response o Genetic theory Cessation of mitosis and cell aging are programmed into genes Telomeres strings of nucleotides on the ends of chromosomes may determine the of times a cell can divide
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