Docstoc

Ecosystem Dynamics_1_

Document Sample
Ecosystem Dynamics_1_ Powered By Docstoc
					Notes – How particles move across a membrane                                                     Biology
        Active transports

Active transports

Objectives - SWBAT
 List and describe the means by which particles move across membranes
 Describe primary, secondary,

Active Transport
   Occurs when:
            o    Cells need to move molecules across membrane against a concentration gradient,
                 from area of low to high areas of concentration
            o    Membrane is impereable to type of material needed
   Cell has to do the work
   Cells expend energy during active transport
            o    70 of the body’s uaable energy is expended on cellular transport
   Use energy to counteract random motion of particles
   Permease (proteins) act as pumps
   Like facilitated diffusion in the sense that carrier proteins facilitate the diffusion
   Energy from cell change shape of permease (pump)
   Change in shape results in pulling particle into (or pushing it out of) a cell


   Way to rid cell of harmful particles – kidney
            o    Maintains greater concentration of waste outside the kidney cells
   Way to bring extra particles into cell
            o    Example – root cells
            o    Retain needed minerals from soil
            o    Continues to bring ions into cell despite high concentration of ions in cell


Primary and secondary active transport
                                   (show video: “Understanding the cell membrane”, part 2, 17 minutes)
   Provides movement for smaller particles
   Primary active transport
            o    ATP provides the energy, phosphate (-P) group attaches to the transport protein
            o    Phosphate group from ATP actuates protein and opens the channel in the protein
            o    Energy release pumps the particles
                         +     +
            o    Ex. Na - K pump – sets up a charge differential for “charging” nerve cells
                            3 Na+ ions pumped out of the cell, 2 K+ ions pumped into the cell
                            Makes external surface of the cell more positive, 3 Na+ ions outside, causes
                         electrical gradient


                                                   -1-                                  Detering 030802
Notes – How particles move across a membrane                                                     Biology
        Active transports

    Secondary active transport
             o   Potential energy of the protein converted to kinetic energy
             o   ATP not required
             o   Co-transport (symport) – 2 particles move in the same direction thru protein pump
                           Fructose and amino acids enter cells using co-transport process
             o   Counter transport (antiport)
                           Charged particle and another ion move in the opposite direction
                           Ca+ ions pumped out, amino acids pumped in


    Active transport example
             o   Animal cells pump sodium ions out of cell and potassium ions into cell
             o   Process uses about 1/3 of your total energy budget
             o   Enable sodium ion concentration to be high outside cell and potassium ion
                 concentration to be high inside cell
             o   These concentration important for muscle contraction, transportation of nerve
                 impulses and absorption of nutrients

                 st
Video – show 1 few minutes of” “How Cells Get Energy”, up to info on aerobic respiration
         shows how ATP is an energy source and how, ADP returns to ATP


Bulk transport - Endocytosis and Exocytosis


    Some materials are too large to pass into a cell by passive or active transport
    Bulk transport – large molecules, food and other substances are packaged in membrane-bound
    sacs and moved across the membrane
    Taken in through endocytosis
    Leave cell by exocytosis
                              (show video: “Understanding the cell membrane”, part 2, 17 minutes)
Endocytosis


    Latin meaning = within - cell – process         … the process of bringing within the cell
    Process in which a cell uses energy to surround and take in large particles
    Particle does not pass through the bilayer
    Engulfs the particle
    That portion of the membrane breaks away and moves in the cell’s interior
    Membrane and its content form a sac or vesicle



                                                  -2-                               Detering 030802
Notes – How particles move across a membrane                                                Biology
        Active transports

   Phagocytosis                                    (pronounced: faegocytosis)
            o   the trapping of a solid waste in this manner is called
            o   cell engulfs a particle with a “cytoplasmic arm”
            o   creates a phagocytotic vessicle


            Exampes:
            o   Amoeba engulfs smaller organisms for food – way unicellular organisms get food
            o   Food vesicle can fuse with a lysosome that contains digestive enzyme
            o   Human white blood cells engulf and digest bacteria and other foreign bodies that get
                into the body
            o   White blood cells engulf and destroy unwanted red blood cells


                         Lysosome
                                 Small sacs
                                 Digest food particles
                                 Form from pinched off pieces from Golgi- apparatus
                                 Enzyme-containing lysosomes are example of chemical packaging
                                  activity of Golgi apparatus


Receptor mediated endocytosis
    o   Binding sites have specific receptors imbedded in the membrane, specific to the substance
    o   Binding site will attach to substance despite concentration of substance in the extracellular
        fluid
    o   Specific particles combine with membrane protein receptors


   Pinocytosis – taking in of liquid droplets or very small particles     (pronounced: peenocytosis)
            o   “cell drinking”
            o   Cell membrane encloses a droplet of fluid and brings it into the cell
            o   Solutes in fluids can be into the cytoplasm


    2 forms of pinocytosis


    o   Substance to be taken in collects on outer surface of membrane
    o   Collects where proteins are located
    o   Vesicle forms, bringing substance into cells


    o   Vesicle forms as binding sites fold in with membrane


                                                -3-                               Detering 030802
Notes – How particles move across a membrane                                                  Biology
        Active transports

     o   Vesicle forms around both the particles and the receptors and moves into the cell
     o   Particles released from the vesicle and used by the cell
     o   Vesicle still containing receptors returns to outer part of cell where it and receptors become
         part of the cell membrane




Exocytosis
    Latin meaning = the process of exiting the cell
    Exocytosis – process used to rid some cells of waste or expel useful substances needed
    elsewhere
    Waste removal
    Move cell products elsewhere
             o   Products fuse with Golgi vesicles
             o   Golgi vesicles then fuse with cell membrane,
             o   Secrete material out of cells
    Substance enclosed in a vesicle, move toward the cell membrane
    Two membranes fuse and the vesicle bursts, expelling materials from the cell


             Golgi apparatus
             o   Packaging and secreting of cell products
             o   Series of flat , membrane bound sac-arranged like stack of pancakes
             o   Materials are modified as they pass through the sacs and eventually excreted


    Exretion
             o   Examples: Urine, sweat


    Secretion
             o   Examples: mucous membranes, intestine




                                                 -4-                               Detering 030802

				
DOCUMENT INFO