Cells and the Cell Theory

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					Cells and the Cell
     Biology-Unit 3
I. The Cell Theory
A. The cell is the basic unit of structure and function
  in living things.
B. The three components of the Cell Theory are:
  1. Cells are the functional units of living things
       --All cells carry on their own life activities
  2. Cells are the structural units of living things
       --All organisms are made up of one or more
  3. New cells arise only from other living cells by
       the process of cell division or reproduction
I. The Cell Theory (cont.)
C. Exceptions to the Cell Theory
1. Mitochondria and Chloroplasts:
    contain their own genetic
    material (DNA) and can
    duplicate themselves.
    Evidence that they are
    descendants of primitive
2. Viruses: consist of DNA          Viruses- Can only reproduce
    surrounded by a protein coat.      inside a living cell but are not
3. Where did the first cell come       cells themselves
II. Cellular Organization
  As organisms become more complex, their
   structures are organized in more complex ways.
   A. Cell: the basic unit of structure and function
   in organisms.
      1. Unicellular: a complete living thing that is
               made of only one cell
Example: ameba, paramecium, euglena
      2. Multicellular: a complete living thing that is
      made up of many cells.
Example: human, palm tree, dog
II. Cellular Organization (cont.)
B. Tissue: a group of cells in an organism that are
    alike in structure and activity.
    Example: muscle tissue, blood, blood vessels,
    nerve tissue, bone, cartilage, etc.
C. Organ: A group of tissues that work together to
    perform a specific function.
    -Example of an Organ: Stomach (made of
    nerves, muscles and blood vessels)
II. Cellular Organization (cont.)
D. Organ System: A group of organs that work together to
  perform a specific function.
  -Example: Digestive System (includes mouth,
  esophagus, stomach, intestines, liver, etc.)

E. Organism: A living thing
Organelle Cell Tissue Organ Organ System
   Organism Species
III. Historical Developments of the
Cell Theory
I. Scientists
A. Robert Hooke
1. Combined 2 sets of lenses
    to form the first compound
2. Used this microscope to
    examine cork and found
    that it is made up of box-
    like structures which he
    called “cells”
III. Historical Developments of the
Cell Theory (cont.)
B. Anton van
1. Constructed a high
   powered simple
2. Viewed pond water
   and found that it
   contained microscopic
   unicellular organisms
   (bacteria, protozoa).
III. Historical Developments of the
Cell Theory (cont.)
IV. Cell Structure
I. Purpose of Cells:
   A. Cells have particular structures to
   perform particular jobs.
   B. These structures perform the actual
   work of the cell-they are called organelles
   (little organs)
IV. Cell Structure (cont.)
A. Cell (plasma) membrane: Separates the
interior of the cell from the surrounding environment.
   1. The membrane regulates the chemical
   composition of the cell by allowing only certain
   molecules to pass into and out of the cell.
       - Large molecules must first be broken down
   outside the cell which allows them to pass
   through. They are then built into large molecules
   inside the cell.
IV. Cell Structure (cont.)
IV. Cell Structure (cont.)
2. The cell membrane maintains homeostasis
  (constant internal environment).
3. The cell membrane is a two-layered
  structure of lipids with proteins embedded
  in them. This is a phospholipid bilayer
IV. Cell Structure (cont.)
IV. Cell Structure (cont.)
a) Some proteins serve as channels through
  which molecules can pass
b) Some proteins function as receptors which
  recognize chemicals in the environment
IV. Cell Structure (cont.)
4. Pinocytosis: “cell drinking”
  Process by which liquid or very small
  particles are taken into the cell and put into
  a vacuole.
5. Phagocytosis: “cell eating”
  Process by which large particles are
  ingested into the cell, placed into a vacuole,
  and digested by a lysosome.
IV. Cell Structure (cont.)
B. Nucleus:
A Large, round, dense body that
   serves as the control center
   for cell metabolism and
1. Nuclear membrane/envelope
   which controls what goes in
   and out of the nucleus.
2. The nucleus contains the
   DNA in a eukaryotic cell.
   DNA is hereditary
   information in the form of
IV. Cell Structure (cont.)
C. Cytoplasm:
  Watery material in which are dissolved many of
  the substances involved in cell metabolism.
  1. Place where most of the cell’s chemical
  reactions take place
IV. Cell Structure (cont.)
D. Endoplasmic Reticulum (ER):
   System of fluid-filled canals
   forming a continuous network
   throughout the cytoplasm.
   1. Used to transport materials
   throughout the cell.
   2. Rough endoplasmic
   reticulum (RER): has
   ribosomes attached.
   3. Smooth endoplasmic
   reticulum: has no ribosomes
   attached to it.
IV. Cell Structure (cont.)
E. Golgi complex:
  Stack of membranes
  that serve as the
  packaging and
  storage center of the
  1. Animals have one
  while plants have
IV. Cell Structure (cont.)
F. Lysosomes:
  Small organelle structures that contain strong
  hydrolytic (digestive) enzymes.
  1. Break down worn out organelles
  2. Disease fighters (eat bacteria)
  3. Found only in animal cells
  4. Used for digestion and absorption of the
  tadpole tail during metamorphosis in frogs
IV. Cell Structure (cont.)
G. Mitochondria: Slipper-
  shaped organelle surrounded
  by membranes.
  1. Inner membrane is highly
  folded forming christae.
  2. Site of cellular
  of the cell.
  3. Contain their own DNA
  and can replicate
IV. Cell Structure (cont.)
H. Centrioles: Pair of cylindrical structures located near the
   nucleus which are involved in cell division.
   1. Only found in animal cells
I. Vacuole: Fluid filled organelles which function as storage
   1. Plants have 1 large vacuole
   2. Animals have few small ones
   3. Contractile vacuole: organelle found in aquatic
   protists used to get rid of excess water.
IV. Cell Structure (cont.)
J. Chloroplast: Double
   membrane bound organelle
   that is found only in plants.
   It serves as the site of
   1. Contains chlorophyll
   2. Contains its own DNA
   and can replicate itself.
IV. Cell Structure (cont.)
K. Cell Wall:
  Rigid, non-living structure which gives the cell
  it’s shape and provides protection.
  1. Composed of cellulose.
  2. Only found around plant cells.
L. Ribosomes:
       Site of protein synthesis within the cell.
V. Tools of the Cytologist
Tools of the Cytologist
I. Methods Used in the Study of Cells
   A. Compound Light Microscope: most
   influenced the development of the cell theory.
        1. Can view living or dead specimens
        2. Measurement: 1000 micrometer (micron)
   = 1 mm
        3. Can magnify 40 to 500 times
V. Tools of the Cytologist
B. Electron Microscope: beam of electrons gives
  great detail and magnification.
      1. Specimen being looked at must be thin,
  dry, and in a vacuum chamber (non-living)
      2. Can magnify 250,000 times
      3. Used to view-micro structures like
  ribosomes or the inside of large structures like
  a chloroplast
V. Tools of the Cytologist
C. Microdissection Apparatus: used to
 perform operations in living cells
 (example: remove a nucleus from a cell)
D. Dissecting Microscope (stereomicroscope): 6 to
  50X magnification
  1. Provides a 3-dimensional image of a
  2. Used to study the external structure of small
  plants and animals (ex. Dissect a fly)
V. Tools of the Cytologist
E. Ultracentrifuge: used to
  separate very light particles
  from one another by their
F. Staining Techniques: used to
  see details when looking at
  cells under the microscope
  1. Two stains: methylene blue
  and Lugol’s iodine

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