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Cells

VIEWS: 8 PAGES: 11

									    Cells
The Basic Units of
      Life
                 Life’s Organization
   All life on Earth is made of one or more cells

   Living things can be:
       One-celled organisms (like bacteria)
       Many-celled organisms (a human has over 2 trillion cells)

   Organization of complex life forms:

                  Cells
                           Tissues
                                  Organs
                                             Systems
                                                   Entire Organism
                   Is It Alive?
For something to be considered alive, it must:

      1.    have a lifespan (birth, growth, death)
      2.    be made of 1 or more cells
      3.    use energy for its activities
      4.    give off wastes
      5.    need water to survive
      6.    respond to its environment
      7.    be able to reproduce
                   Cell Organelles
   Cells have:                    Other cell organelles:
    many different organelles          Endoplasmic reticulum (ER)
    for different functions            Golgi bodies
                                       Ribosomes
   Typical cell organelles:           Vacuoles
       Cell membrane
       Cytoplasm                  Only in plant cells:
       Nucleus                        Chloroplasts
       Chromosomes                    Cell walls
       Mitochondria
                     Cell Organelles
   Cell membrane:    regulates what enters and exits the cells,
                      for example: nutrients and wastes

   Cytoplasm:        gel-like material (mostly water)
                      moves materials around (streaming)

   Nucleus:          cell’s command center
                      controls and directs all cell activities

   Chromosomes:      threadlike; made of DNA and protein
                      DNA molecule contains all genetic instructions

   Mitochondria:     “power plants” of cells; cell respiration occurs here:
                      nutrients + oxygen → carbon dioxide + water + energy
                      ( glucose + O2 →            CO2        + H2O + energy)
                    Cell Organelles
   Endoplasmic       canal network inside the cell
    Reticulum (ER):   provides messenger service through the
                      cell

   Golgi Bodies:     store chemicals
                      “finish processing” of chemicals made by
                      cells

   Ribosomes:        attached to ER
                      make proteins for use by the cell

   Vacuoles:         storage areas for water, food, other
                      chemicals; largest in plant cells
                      Plant Cells
   Plant cells have two organelles not found in animal cells:
                 chloroplasts and cell walls
   Chloroplasts:
      Plants make food using photosynthesis:

         carbon dioxide + water + energy → nutrients + oxygen
                ( CO2    + H2O + sunlight → glucose + O2 )
      Contain chlorophyll to absorb the sun’s light energy

   Cell walls:
      Made of cellulose (tough plant fiber)

      Rigid structure outside cell membrane

      Provides support for the cell
              A “Typical” Plant Cell
Chloroplast
                                   Nucleus

Endoplasmic
Reticulum                          Chromosomes

Ribosomes
                                   Mitochondria

Cell membrane


                                   Cell Wall

Vacuole

Cytoplasm
                                   Golgi Bodies
    Diffusion: How Materials Move
   Materials like nutrients and wastes enter and leave a
    cell by diffusion

   Diffusion =      the movement of molecules from
                     areas of higher concentration to
                     areas of lower concentration

   Has anyone in the house ever burned toast?
    How do you know it?
                        Diffusion
   How does this process work?
    Materials will always move to where they’re less concentrated:




           Before…                    …After: equilibrium
                Diffusion
View diffusion animation
 http://www.indiana.edu/~phys215/lecture/lecn
  otes/lecgraphics/diffusion2.gif

								
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