Cell Anatomy Powerpoint Lecture by jamesdauray

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									Anatomy of Cells


   Introduction to Biology
     The Discovery of Cells
• In Holland, Anton van
  Leeuwenhoek examined
  pond water and a sample
  taken from a human
  mouth.
• He drew the organisms he
  saw—which today we call
  bacteria.
• Leeuwenhoek examined
  as many types of cells as
  he could. He even
  observed his own semen!
            Overview: The
          Importance of Cells
• The early discoveries of cells are summarized in
  the cell theory, a fundamental concept of biology.
• The cell theory states:
   o All living things are made up of cells.
   o Cells are the basic units of structure and function in living things.
   o New cells are produced from existing cells.
       Origin of Cellular Life
• The Earth formed about 4.6 billion years ago.
   o For about 500 million years, the Earth was continually
     bombarded by chunks of rock and ice in the solar system.
• The early atmosphere of Earth contained:
   o   Water vapor H2O
   o   Nitrogen N2
   o   Carbon dioxide CO2
   o   Methane CH4
   o   Ammonia NH3
      Origin of Cellular Life
• How did life arise from such a harsh environment?
• Two scientists designed a model of what conditions
  were like on Earth at this time.
   o This is called the Miller-Urey Apparatus
    Miller-Urey Apparatus




• This apparatus simulated three important conditions
  on Earth:
   – The high amount of lightning
   – Heat and gases released by volcanic activity
   – Water vapor present in the atmosphere.
       Results of Miller-Urey
            Apparatus
• Simple compounds including water (H2O), methane
  (CH4), ammonia (NH3), and hydrogen (H2) were used to
  simulate the atmosphere.
• After 2 weeks, 10-15% of the carbon had been used to
  form sugars, amino acids, and parts of nucleic acids.
  o These simple organic compounds could have produced the
    proteins, lipids, and carbohydrates that make up life today.
                The First Cells
• The first life forms on Earth were likely single-celled
  prokaryotic organisms.
   o Prokaryotic organisms are single-celled organisms that do not
     have a nucleus.
      • Their DNA or RNA is usually floating freely inside the cell.
   o Prokaryotic cells also do not have any membrane bound
     organelles.
                Pili

                       Nucleoid

                         Ribosomes

                            Plasma
                            membrane

                             Cell wall
    Bacterial
chromosome                         Capsule
                                                               0.5 µm
                                  Flagella



   A typical                                 A thin section through the
   rod-shaped                                bacterium Bacillus
   bacterium                                 coagulans (TEM)
 Parts of a Prokaryotic Cell
• Nucleoid – Area where DNA or RNA is located. Not
  enclosed in a membrane like a nucleus.
• Ribosomes – Small structures that use DNA or RNA
  instructions to produce proteins.
• Pili – Hollow, hair-like structures that can be used to
  exchange genes.
• Flagella – Spin to produce movement.
• Cell membrane – Controls what leaves or enters the
  cell
           Eukaryotic Cells
• Eukaryotes are organisms with
  much larger and more
  complex cells than
  prokaryotes.
   • DNA is in a nucleus that is
     bounded by a nuclear
     membrane.
   • Have membrane-bound
     organelles
• The largest eukaryotic cells
  are 0.1mm to 1.0mm in size.
  Why haven’t they evolved
  any larger?
LE 6-7
                                 Surface area increases while
    • Volume represents the     Total volume remains constant
      size of the cell.
    • Surface area represents
      the amount of cell
      membrane to transport
                                5
      food, waste, water, and
                                              1
      oxygen.
                          1

    Total surface area




    Total volume




    Surface-to-volume
    ratio
LE 6-7
                                        Surface area increases while
    • A cell with a volume of          Total volume remains constant
      1mm3 will have a total
      surface area of 6mm2.
    • This provides plenty of
      area for the cell to
                                       5
      absorb what it needs.
                                                     1
                               1

    Total surface area
    (height x width x              6
    number of sides x
    number of boxes)

    Total volume
    (height x width x length       1
    X number of boxes)

    Surface-to-volume
    ratio
                                   6
    (surface area  volume)
LE 6-7
                                     Surface area increases while
  • A larger cell with a            Total volume remains constant
    volume of 125mm3 will
    only have a surface area
    of 150mm2.
  • This cell will not be able to
                                    5
    transport wastes and
                                                  1
    nutrients fast enough.
                               1

    Total surface area
    (height x width x                    150
    number of sides x
    number of boxes)

    Total volume
    (height x width x length             125
    X number of boxes)

    Surface-to-volume
    ratio
                                          1.2
    (surface area  volume)
LE 6-7
                                        Surface area increases while
    • If the larger cell is instead    Total volume remains constant
      broken down into 125
      smaller cells, it will once
      again have enough
      surface area.
                                       5
    • This is why multicellular
                                                     1
      organisms exist!
                               1

    Total surface area
    (height x width x              6        150          750
    number of sides x
    number of boxes)

    Total volume
    (height x width x length       1        125          125
    X number of boxes)

    Surface-to-volume
    ratio
                                   6         1.2           6
    (surface area  volume)
          Cell Organization
• The eukaryotic cell can be divided into two major parts: the
  nucleus and the cytoplasm.
• The cytoplasm is the fluid portion of the cell outside the
  nucleus.
• Prokaryotic cells have cytoplasm as well, even though they
  do not have a nucleus.
  Eukaryotic Cell Anatomy
• A eukaryotic cell has internal membranes that
  partition the cell into organelles.
   o Organelles are small structures within cells that have specific jobs.

• Plant and animal cells have most of the same
  organelles, although there are a few differences.
                         ENDOPLASMIC RETICULUM (ER
                                                                Nuclear envelope
             Flagellum      Rough ER   Smooth ER
                                                                Nucleolus            NUCLEUS

                                                                Chromatin




         Centrosome
                                                                                   Plasma membrane




     CYTOSKELETON

       Microfilaments

Intermediate filaments

         Microtubules

                                                                                 Ribosomes:




       Microvilli


                                                                 Golgi apparatus


     Peroxisome


                            Mitochondrion
                                                     Lysosome

                                                                    In animal cells but not plant cells:
                                                                    Lysosomes
                                                                    Centrioles
                                                                    Flagella (in some plant sperm)
LE 6-9b
                         Nuclear
                        envelope       Rough
          NUCLEUS      Nucleolus       endoplasmic
                                       reticulum
                       Chromatin
                                                     Smooth
            Centrosome                               endoplasmic
                                                     reticulum


                                                                      Ribosomes
                                                                      (small brown dots)


                                                                   Central vacuole
               Golgi
           apparatus
                                                                   Microfilaments
                                                                   Intermediate      CYTOSKELETON
                                                                   filaments
                                                                   Microtubules




            Mitochondrion
              Peroxisome
                   Plasma                                     Chloroplast
                 membrane

                           Cell wall
                                            Plasmodesmata
              Wall of adjacent cell
                                                             In plant cells but not animal cells:
                                                             Chloroplasts
                                                             Central vacuole and tonoplast
                                                             Cell wall
                                                             Plasmodesmata
                The Nucleus
• The nucleus contains most of the cell’s genes and is
  usually the largest organelle.
• The nuclear envelope is a membrane that encloses
  the nucleus, separating it from the cytoplasm.
• In the same way that the main office controls a large
  factory, the nucleus is the control center of the cell.
• The nucleus contains nearly all the cell’s DNA and,
  with it, the coded instructions for making proteins and
  other important molecules.
    The Nuclear Membrane
• The nuclear envelope is dotted with thousands of
  nuclear pores, which allow material to move into and
  out of the nucleus.
• The nucleus mainly contains chromatin— the cell’s
  DNA instructions joined with proteins.
    The Nuclear Membrane
• The nucleus also contains a small
  dense region called the
  nucleolus.
• The nucleolus produces
  ribosomes, which are needed to
  build proteins.
      Organelles that Build
           Proteins
• Because proteins carry out so many of the essential
  functions of living things, a big part of the cell is
  devoted producing and transporting them.

• Proteins are synthesized on ribosomes, which can be
  found in two places:
   o Freely floating in the cytoplasm
   o Attached to the endoplasmic reticulum
         Ribosomes: Protein
              Factories
• Ribosomes are particles made of RNA and protein
  o Ribosomes produce proteins by following coded instructions
    that come from DNA.
  o Each ribosome is like a small machine in a factory, turning out
    proteins on orders that come from its DNA ―boss.‖
    Endoplasmic Reticulum
• The endoplasmic reticulum (ER) is a huge membrane
  that is connected to the nuclear membrane.
• There are two distinct regions of ER:
  o Smooth ER, which lacks ribosomes
  o Rough ER, with ribosomes studding its surface
        Smooth Endoplasmic
            Reticulum
• The smooth endoplasmic reticulum:
   o   Synthesizes lipids
   o   Metabolizes carbohydrates
   o   Stores calcium
   o   Detoxifies poison
• The smooth endoplasmic reticulum does not contain
  any ribosomes, so it is unable to synthesize proteins.
      Rough Endoplasmic
          Reticulum
• The rough ER
  o Holds ribosomes
  o Produces any proteins needed by the cell.
       The Golgi Apparatus
• The Golgi apparatus is a series of flattened membrane
  sacs in the cytoplasm.
• Functions of the Golgi apparatus:
   o Modifies, sorts, and packages materials into transport vesicles
     for storage or transport out of the cell.
   o A typical path for a protein produced by the cell:
   o Rough ER → Golgi → Cell membrane → Released by cell
 LE 6-16-1


                                Nucleus




                                Rough ER




Smooth ER
             Nuclear envelope
 LE 6-16-2


                                                  Nucleus




                                                  Rough ER




Smooth ER
             Nuclear envelope   cis Golgi



                                                    Transport vesicle




                                    trans Golgi
 LE 6-16-3


                                                  Nucleus




                                                  Rough ER




Smooth ER
             Nuclear envelope   cis Golgi



                                                    Transport vesicle




                                                             Plasma
                                                             membrane
                                    trans Golgi
    Organelles that Store,
    Clean Up, and Support
• These are organelles that help the cell maintain its
  shape, clean up wastes, and store material needed
  later.
   o Vacuoles
   o Lysosomes
   o Cytoskeleton
                     Vacuoles
• Vesicles and vacuoles are membrane-bound sacs
  that store many materials.
• Plant cells often have one large central vacuole. This
  fills with water, making the cell rigid.
   o When they are empty and dry, plants wilt!
                   Lysosomes
• Lysosomes serve as the cell’s cleanup crew.
• A lysosome is full of enzymes that can digest proteins,
  lipids, polysaccharides, and nucleic acids.
   o Can also breakdown old organelles so they can be re-used.




                     Animation: Lysosome Formation
                 Cytoskeleton
• The cytoskeleton is a network of protein filaments that
  give the cell shape.
   o Can also help transport materials across the cell.
• Centrioles are part of the cytoskeleton that help move
  chromosomes during cell division.
    Organelles that Capture
     and Release Energy
• All life requires energy.
• Organisms either can get their energy from sunlight
  via photosynthesis, or by eating other organisms via
  cell respiration.
• Photosynthesis occurs in chloroplasts.
• Cell respiration occurs in mitochondria.
             Mitochondria
• Mitochondria are the power plants of the cell.
• They convert the chemical energy stored in food into
  smaller molecules for the cell to use.
• Mitochondria have two membranes, outer and inner.
• The inner membrane is folded up to increase the
  amount of surface area to do chemical reactions.
             Chloroplasts
• Chloroplasts contain the green pigment
  chlorophyll, as well as enzymes and other
  molecules that function in photosynthesis
• Chloroplasts are found in leaves and other
  green organs of plants and in algae
         Plasma Membrane
• The plasma membrane is a selective barrier.
  o Allows passage of oxygen, nutrients into the cell,
    and waste out of the cell.
• The general structure of a biological
  membrane is a double layer of phospholipids
  o This allows the cell to control what goes in and
    out.
                   Cell Wall
• The cell wall is made of cellulose and serves as
  support and protection for the cell.
• Animals do not have cell walls, but plants, fungi, and
  algae do.
• The cell wall is outside of the cell membrane.
     Plants: Plasmodesmata
• The cell wall is so thick that oxygen, nutrients, water,
  and waste cannot travel easily through.
• Plasmodesmata are channels that perforate plant cell
  walls
• Through plasmodesmata, water and other small
  molecules can enter the cell.
    Animals: Tight Junctions,
 Desmosomes, and Gap Junctions
• Although animal cells do not have cell walls, they also
  have special structures within their cell membranes.
• At tight junctions, membranes of neighboring cells are
  pressed together, preventing leakage of extracellular
  fluid.
   o Example: Lining of small intestines
• Desmosomes (anchoring junctions) fasten cells
  together into strong sheets
   o Example: Layers of outer skin cells
• Gap junctions (communicating junctions) provide
  cytoplasmic channels between adjacent cells
   o Example: Cardiac muscle cells
LE 6-31


                        Tight junctions prevent                Tight junction
                        fluid from moving
                        across a layer of cells



                                                                                        0.5 µm




                                        Tight junction

                                Intermediate
                                filaments
                                       Desmosome

                                                                                         1 µm
                                            Gap
              Space                         junctions
              between
              cells


  Plasma membranes
  of adjacent cells
                                                                         Gap junction
                                                         Extracellular
                                                         matrix
                                                                                        0.1 µm
The Cell: A Living Unit Greater Than the
                Sum of Its Parts
• Cells rely on the integration of structures and
  organelles in order to function
• For example, a macrophage’s ability to destroy
  bacteria involves the whole cell, coordinating
  components such as the cytoskeleton, lysosomes, and
  plasma membrane

								
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