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					      UNIT 5

Eukaryotic Cells:
   Protists
        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:
  • All living things are made up of cells.
  • Cells are the basic units of structure and function in living things.
  • New cells are produced from existing cells.
• Prokaryotic cells are small and have no
  membrane-bound organelles (including a
  nucleus).
             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
    • 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                                   750
    number of sides x
    number of boxes)

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

    Surface-to-volume
    ratio
                                                          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.
• The nucleus
  contains the cell’s
  DNA.
• 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.
  • 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.
                        PROTISTS

• The largest and most diverse
  kingdom of eukaryotes are called
  protists.
  • Most protists are unicellular, or made
  of a single cell only.
  • Colonial protists are still unicellular
  but live together with other members of
  the species.
  • Multicellular protists are made of
  more than one cell.
  THE SUPERGROUPS OF EUKARYOTES


• There are five “supergroups” of eukaryotes that include
  protists:
   •   Excavata (“hollow” )
   •   Chromalveolata (“color and cavity”)
   •   Rhizaria (“root” like pseudopods)
   •   Archaeplastida (protozoa with chloroplasts like plants)
   •   Unikonta (“one flagellum”)
                   EXCAVATA

• Excavata in Latin means “to make hollow”.
• Many members of this group have large grooves in
  their cells to help in feeding.
• A good example of the excavata group is Euglena.
                       EUGLENA

• Euglena are mixotrophs.
  This means they can produce
  their own food from sunlight
  or consume it from the
  environment.
   • They have chloroplasts,
     which are organelles that
     can absorb sunlight and
     convert its energy into
     sugars.
   • Move with a flagella.
   • An eyespot (stigma)
     helps it to move toward
     light sources.
                           EUGLENA

• Euglena have cell membranes and cytoplasm like every
  other cell.
   • The cell membrane controls what enters and leaves the cell.
   • The cytoplasm holds the organelles and gives the cell its shape.
• They do not have a cell wall like
  bacteria do, but they have a pellicle
  instead.
   • The pellicle is made of protein fibers
     that can stretch and spiral over each
     other.
   • This gives the euglena the ability to be
     highly flexible as it moves.
         EUGLENA MOVEMENT




• Look for the movement of the flagella and pellicle.
                        OSMOSIS

• Osmosis is the passive movement of water across cell
  membranes.
   • Water tends to move towards areas of higher solutes (sugars,
     salts, etc).
• Hypertonic solutions have more solute than any
  cells present.
   • Saltwater
• Hypotonic solutions have less solute.
   • Distilled water
• Isotonic solutions have an equal amount of solute.
   • Ringer’s Solution (IV bags)
        HYPOTONIC SOLUTIONS

• Red blood cells burst in   • Plant cells don’t have this
  distilled water. The         problem. Their cell walls
  water rushes into the        prevent them from
  cells.                       bursting.
                       EUGLENA

• Euglena live in freshwater ponds, which are hypotonic
  solutions.
• To protect them from osmosis, they have a special
  organelle called a contractile vacuole.
   • Vacuoles are organelles that most eukaryotes have to store
     liquids like water.
   • Euglena use a contractile vacuole to pump out excess water,
     so they don’t explode.
            Gullet

      Reservoir

 Nucleus                           Stigma
                                   (Eyespot)
Flagella                      Contractile
                              Vacuole
                            Cytoplasm


                        Cell Membrane

                     Chloroplast
               (IN)FAMOUS EXCAVATES

• Trichomonas vaginalis.
• Unicellular protozoa with flagella.
  Reproduce sexually and asexually.
• Protozoa that infects the urethra
  and vagina of women, causing the
  STD called “trich”.
   • It only infects women with a pH that
                                                    • The damage this
     is much not as acidic as normal.
  • pH of about 4 is normal; pH of 5-6 is at-risk
                                                    parasite causes also
                                                    increases risk of
                                                    HIV infection.
             (IN)FAMOUS EXCAVATES

• Trypanosomas are flagellated protozoa that infect
  humans through the bite of the African tsetse fly. They
  cause a disease called African Sleeping Sickness.
• This protist has the ability
  to constantly generate new
  surface proteins so the immune
  system is never able to recognize it.
• It can pass through the blood-brain barrier and begin
  destroying neurons.
   • This causes the symptoms, including tiredness, confusion, lack
     of muscle coordination, coma, and eventually death.
AFRICAN SLEEPING SICKNESS



             • This is a smear of red
               blood cells from a
               patient infected with
               the disease.
                CHROMALVEOLATES

• Chromalveolates are very similar to plants, because they
  have chloroplasts for absorbing sunlight and cell walls.
• They have cell walls made of a polysaccharide called
  cellulose that protects the cell.
• Not all chromalveolates are autotrophs – some are
  deadly parasites.
   • These have a special organelle that helps them invade cells
     instead of performing photosynthesis.
                        CILIATES

• Paramecium are oval-shaped protists covered with
  hair-like cilia all over their cell membrane.
   • The cilia move together like oars to propel the paramecium.
• Paramecia ingest their food through an opening called
  the oral groove.
   • When enough food has accumulated in the gullet, it enters
     the cell through a food vacuole.
• A special opening called the anal pore is also present,
  to get rid of any leftover waste.
        PARAMECIUM FEEDING




Watch the gullet and the formation of the food vacuole.
                   PARAMECIUM

• Paramecia also have a contractile vacuole that
  continuously pumps water out so they don’t burst.
   • This looks like a pulse or a heartbeat.
   • The water is pushed out the excretory pore.
• A paramecium will have two nuclei:
   • The macronucleus contains most of the ciliates DNA.
   • The micronucleus can be traded with other ciliates
                 Cell
                 Membrane                  Contractile
                                           Vacuole


                                           Cilia
                                           Cytoplasm
                                         Micronucleus
                                        Macronucleus

   Contractile                     Oral Groove
   Vacuole
                                   Mouth Pore
                                Gullet
Food Vacuole                  Food Vacuole
                            Anal Pore
                         DIATOMS

• Diatoms are a type of algae, a protist that closely
  resembles a plant.
   • No ability to move independently.
   • Unicellular.
• Contain an unusual cell wall that is partially made of
  silicon dioxide (same as glass) with an intricate pattern
  of grooves and holes.
   • The cell wall is so strong, that live diatoms can survive a
     crushing force as strong as the weight of the elephant.
• Most diatoms reproduce asexually; each new cell
  receives half of a cell wall, then completes the other
  half on its own.
DIATOMS
                   BROWN ALGAE

• Brown algae are non-
  motile, multicellular,
  and live in saltwater.
• Most of what we call
  “seaweed” are actually
  brown algae.
                (IN)FAMOUS
             CHROMOALVEOLATES
• Rapid growth of one
  type of chromalveolate
  is responsible for
  causing “red tides,” or
  heavy concentrations
  of protozoa and algae
  in water.
               (IN)FAMOUS
            CHROMOALVEOLATES
• Plasmodium is a type of protozoa that lives in both
  humans and a tropical mosquito.
   • Causes the disease malaria.
• The plasmodium reproduces sexually inside a
  mosquito, then releases the offspring into its saliva.
• The plasmodium then enters the human blood stream
  and infect red blood cells and liver cells.
   • They reproduce asexually inside the cells, then burst out of
     them, destroying the cell.
                      MALARIA

• Plasmodia reproduce
  asexually inside the
  cells, then burst out of
  them, destroying the
  cell.
• They complete their
  life cycle within the
  gut of a mosquito,
  which spreads them to
  another host.
                      MALARIA

• Malaria has
  plagued humans
  living near the
  equator for
  thousands of
  years.
• The best way to
  deal with the
  disease is to try
  to avoid and kill
  the mosquito
  that spreads it.
      OOMYCETES (WATER MOLDS AND
           THEIR RELATIVES)

• The potato blight is caused by a
  water mold.
   • Water molds are protists that closely
     resemble fungi.
• Reproduce by releasing spores.
• Get energy by invading plant
  tissue.
• One type of water mold infects
  the stalk and stem of potato
  plants, turning them to black
  slime.
   • The Irish famine of the 19th century
     was largely caused by this protozoa.
                       RHIZARIANS

• This is a group of protozoa
  that all have thread-like
  pseudopodia, or “false feet”.
• Pseudopods are actually
  extensions of cytoplasm that
  can bulge from the cell of the
  protozoa and attach to a
  surface farther away.
   • This enables them to move
     freely on any hard surface.
         (IN)FAMOUS RHIZARIANS

• Dysentery is a disease of the intestine that causes
  severe diarrhea containing mucus and blood.
• A type of amoeba burrows into the walls of the
  intestines, causing the disease.
• A group of amoebas can group together and form a
  hard, protective shell called a cyst.
   • The host passes the cyst in its feces. This is how dysentery is
     spread.
      (IN)FAMOUS RHIZARIANS




Large intestine cells with dysentery spores throughout.
               ARCHAEPLASTIDA

• Members of this group of protists have two major
  organelles – mitochondria and chloroplasts.
• Both organelles deal with energy:
   • Mitochondria take simple sugars (e.g. glucose) and
     break them down into ATP, the smallest molecule of
     energy.
   • Chloroplasts absorb sunlight,
     using the energy to create
     energy-rich sugars (e.g. glucose)
     from carbon dioxide.
    ENDOSYMBIOSIS IN EUKARYOTIC
           EVOLUTION

• There is now considerable evidence that the chloroplasts
  and mitochondria found in eukaryotes originated in
  prokaryotes.
   • The Endosymbiotic theory states that chloroplasts were
     originally bacteria that were ingested by larger cells.
• They grew to live together in a mutualistic relationship
  (both benefit).
   • Mitochondria came from a similar source.
           CHLOROPLASTS AND
            MITOCHONDRIA
• Both organelles have a double-membrane (similar to
  bacteria) and their own DNA.
• There are two main groups of photosynthetic algae: red
  algae and green algae.
• The different colors are the result of different pigments
  used in photosynthesis.
                  UNIKONTA

• Protists with lobe-shaped pseudopods.
• The most common example of protist in this group is
  the amoeba.
                       AMOEBAS

• Amoebas have a pseudopod for movement.
• They also have a contractile vacuole that can pump water
  in or out of the cell to maintain its size.
• Reproduce asexually.
• DNA contained in a
  single nucleus.
• A special organelle called
  a lysosome digests any
  ingested food particles.
            AMOEBA MOVEMENT




Watch the streaming of cytoplasm as the amoeba extends its
pseudopods.
                           Pseudopod



                                          Food
               Excretion



Digestion
                                       Food Vacuole
(Lysosome + Food
                                       (Ingestion)
Vacuole)
     Nucleus
     Lysosome
                                        Contractile Vacuole
                                        (Expelling water)
   Cytoplasm
                                       Contractile
                                       Vacuole

				
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Description: A lecture Powerpoint for a high-school or introductory college level biology course covering the protists.
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