CTYOSKELETON- provides the cell with an internal framework- elaborate series of protein rods thru out cytosolo microtubules dynamic hollow tubes most radiate from centrosome determine overall shape of cell and distribution of organelleso microfilaments dynamic actin strands attached to cytoplasmic side of plasma membrane involved in cell motility, change in shape, endocytosis, and exocytosiso intermediate filaments tough, insoluble ropelike protein fibers resist pulling forces on the cell and attach to desmosomesCELLULAR PROJECTIONS- not found in all cells- microvillio finger-like projections that increase surface area for absorption, contain actin- used for movement:o cilia move materials across the cell surface located in the respiratory system to move mucuso flagella propel the cell the only flagellated cell in the human body is spermMEMBRANE JUNCTIONS- tight junctionso impermeable junctionso bind cells together into leakproof sheets- desmosomeso anchoring junctions that prevent cells from being pulled apart agst mechanical stress- gap junctionso allow communication bw cellso composed of connexonMEMBRANE TRANSPORT- two major classeso 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 osmosiso ACTIVE processes Energy required directly/indirectly Occurs only in living cell membraneso Active transport by solute pumping (primary vs secondary)o Vesicular transport: exocytosis, endocytosis (phagocytosis and pinocytosis), transcytosisTONICITY- Ability of a solution to cause a cell to shrink or swell- Isotonic: solution w/ same solute concentration as that of the cytosol- 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 agingo Immune system disorders: autoimmune responses and progressive weakening of the immune responseo 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
View Full Document
Unlocking...