Eukaryotic Membranes: Plastids and Vacuoles

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Eukaryotic Membranes Plastids and Vacuoles

• Vacuoles are single membrane sacs that separate
  some substance from the cytosol.

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Eukaryotic Membranes Plastids and Vacuoles

• Vacuoles have varied functions
• Central vacuole in plants is for support and
  storage of metabolic wastes
• there are food storage vacuoles
• there are waste storage vacuoles

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Eukaryotic Membranes Cytoskeleton

• Organelles do not drift about the cytoplasm
  haphazardly, rather they are attached to a
  network of protein fibers called the cytoskeleton

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Eukaryotic Membranes Cytoskeleton

• Parts of complex metabolic pathways may be
  fastened in sequence to the cytoskeleton so that
  molecules pass from one enzyme to the next.

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Eukaryotic Membranes Cytoskeleton

• The cytoskeleton is constructed of
• Microfilaments (thin)
• Intermediate filaments (medium)
• Microtubules (thick)

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Eukaryotic Membranes Cytoskeleton

• The cytoskeleton performs the following important
  functions
• Cell shape without cell walls, the
  cytoskeleton, especially networks of intermediate
  filaments, determines the shape of the cell

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Eukaryotic Membranes Cytoskeleton

• 2. Cell movement the assembly, disassembly,
  and sliding of microfilaments and microtubules
  causes cell movement. Cell movement includes
  both the familiar crawling of amoebae and white
  blood cells and the migration and shape changes
  that occur during the development of
  multicellular organisms.

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Eukaryotic Membranes Cytoskeleton

• 3. Organelle Movement Microtubules and
  microfilaments move organelles from place to
  place within a cell. For example, microfilaments
  attach to vesicles formed during endocytosis,
  when large particles are engulfed by the plasma
  membrane and pull the vesicles into the cell.
  Vesicles budded off the ER and Golgi complex are
  probably guided by the cytoskeleton as well.

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Eukaryotic Membranes Cytoskeleton

• 4. Cell division microtubules and
  microfilaments are essential to cell division in
  eukaryotic cells. First, when eukaryotic nuclei
  divide, microtubules move the chormosomes into
  the daughter nuclei. Second, in animal cells,
  division of the cytoplasm of a single parent cell
  into two daughter cells results from the
  contraction of a ring of microfilaments that
  pinch the waist of the parent c ell around the
  middle.

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Eukaryotic Membranes Flagella and Cillia

• Cilia and flagella are slender extensions of the
  plasma membrane.
• Each contains a ring of nine fused pairs of
  microtublules in the center of a ring
  arrangement.
• The main difference in these two is the number,
  length, and direction of force.

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Eukaryotic Membranes Flagella and Cillia

• Cilia are short and numerous. They provide
  force in a direction parallel to the plasma
  membrane. oars

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Eukaryotic Membranes Flagella and Cillia

• Flagella are long, not numerous, and provide
  forse perpendicular to the plasma membrane.
  motorboat

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Eukaryotic Membranes Centrioles

• Centrioles are short, barrel-shaped rings of
  microtubules.
• Their function will be discussed later