Bio Cytoskeleton by 4SJ1VCK7

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  Cristina Botello-Godoy, Karina Garcia,
       Takara Reed, Aida Rogonich
        Eukaryotic vs. Prokaryotic
• Animals, fungi,              • Bacteria
  protozoans, algae, etc.      • Smaller & less complex,
• Much larger & more             as are the cells
  complex, as are the cells    • Structure’s include: shape
• Structure’s include: shape     & strong cell wall, cell
  & strong cell wall, allow      division
  for cell movement (within
  cells & endocytosis), cell
     Prokaryotic Cytoskeleton
• Recent study has found that bacteria cells
  too consist of a cytoskeleton
• Research is based on the fact that the
  proteins of prokaryotic & eukaryotic cells
  are homologues
• Evolution is diverse between the two cell
  types, so more concepts allowed for this
     Prokaryotic Cytoskeleton
• Network of structural filaments
• 3-D structure
• Maintains cell shape, structure, protection,
  polarity, and cell division
• Some structures are still UNIDENTIFIED
• Proteins similar to those of eukaryotic cells
           Protein Functions
FtsZ:                      MreB:
• tubulin-like             • actin-like
• forms filaments, but     • determines cell shape
  they do not group into   • positions polar
  tubules                    proteins
• maintains                • forms a network (helix
  organization               shaped) under the
• required for cell          cytoplasmic
  division                   membrane, that
                             directs proteins
             Protein Functions
CreS:                          ParM:
• crescentin                   • actin-like
• intermediate filament like   • allow for cell division
• maintains cell shape and     • acts like kinetochore
  form of bacteria               complez
• filament connects from       • separation of plasmids by
  pole to pole                   the filaments is
                                 analogous to
                                 microtubules allowing cell
                                 division during eukaryotic
         Cytoskeleton Function
• The Cytoskeleton has many important functions. One of
  its most important functions is to provide structure for the
  cell, it makes sense if you break up the word cyto-
• -The cytoskeleton also acts as a scaffolding, with this the
  organelles in the cell are able to stay attached.
• -The cytoskeleton is also used for the movement of the
  cell. The internal movement of cell organelles, as well as
  cell locomotion and muscle fiber contraction could not
  take place if it wasn’t for the cytoskeleton.
• -The cytoskeleton is also required for the division of cells
  during mitosis or meiosis.
  Endoplasmic Reticulum (E.R.)
• The Endoplasmic Reticulum is the factory in the cell that produces
  proteins and lipids of most of the cells’ s organelles.
• The E.R is mainly responsible for transporting proteins and other
  carbohydrates to wherever they are needed in the cell.
• The E.R is composed of many folds, say you fold a piece of gum
  over and over that’s how the E.R looks.
• There are two types of E.R, a Rough E.R and a Smooth E.R
• The Rough E.R is rough because it has ribosome attached to it. In
  the Rough E.R proteins are made .
• The Smooth E.R doesn’t have any thing attached to it, that’s why its
  called smooth
• The Smooth E.R is the one that releases the proteins produced in
  the Rough E.R
                Cell Shape
• The cell shape depends on what type of
  cell it is
• If the cell is an animal cell than most likely
  the cell is circular because it doesn’t
  contain a cell wall
• If the cell is rectangular or like a square
  then the cell is an animal cell, the cell
  takes the shape of the cell wall
      Cytoskeleton Structure
• Imagine walking into George’s basement.
  All you see is a bunch of glow in the dark
  cables hanging over your head. These
  cables surround the machines that operate
  our school. These cables are the
  cytoskeleton, which surrounds the cells
  that help function our body. =)
      Cytoskeleton Structure
• The Cytoskeleton is a complex three-
  dimensional structure that is found in
  the cytoplasm of the cell. It’s composed
  of fibers primary microtubules being the
  thickest of three, microfilaments, the
  thinnest, and intermediate filaments in
  the middle range.
      • Microtubules are one of the
        components of the
      • They are rigid hollow rods that
        have a diameter of 25
        nanometers and length of
        anywhere between 200
        nanometers and 25
      • Microtubules serve as
        structural components within
        cells and are involved in many
        cellular processes including
        mitosis, cytokinesis, and
        vesicular transport.
Centrosomes, Centrioles, Cilia &
                • Centrosomes organize the
                • They also regulate cell-cycle
                • This occurs in the cytoplasm
                  attached to the outside of the
                • In nine triplet sets (star
                  shaped), microtubules form
                  Centrioles surrounded by a
                  solid mass of protein called the
                  “pericentriolar material.”
                • In nine doublets oriented
                  about additional microtubules
                  (wheel-shaped) microtubules
                  form cilia & flagella.
Centrosomes & Centrioles
      Centrosomes & Centrioles
                               ANIMAL CELLS:
•   The centrosome, also called the •       The two centrioles are arranged
    "microtubule organizing center“         so that one is perpendicular to the
    (MTOC), is a region in the cell         other.
    where microtubles are formed.       •   During animal cell division, the
•   Within an animal cell centrosome,       centrosome divides and the
    there is a pair of small organelles     centrioles replicate which results
    known as the centrioles which           in two centrosomes that each
    each make up of a ring of nine          have its own pair of centrioles.
    groups of microtubules. (see        •   The two centrosomes move to
    picture).                               opposite ends of the nucleus, and
                                            from each centrosome,
                                            microtubules grow into a "spindle"
                                            which is responsible for separating
                                            replicated chromosomes into the
                                            two daughter cells (Mitosis
    Centrosomes & Centrioles
              • PLANT CELLS:
• Plant cells have centrosomes that function
  much like animal cell centrosomes.
  However, unlike centrosomes in animal
  cells, they do not have centrioles.
Cilia & Flagella
        •   Both cilia and flagella are created from
            microtubules, and both supply:
             –   “Locomotion” for the cells (like sperm)
             –   And the movement of fluid past the
        •   Both have the same basic structure.
             –   If the microtubules are short, they are
             –   Or only one or a few long ones, they
                 are flagella.
        •   Each cilium or flagellum is made of:
        •   a cylindrical collection of 9 evenly-
            spaced microtubules, each with an
            incomplete microtubule attached to it.
            This gives the structure a "figure 8"
            appearance when view in cross
            section. (see bottom picture).
        •   2 single microtubules run up through
            the center of the bundle, completing
            the so-called "9+2" pattern.
        •   The entire assembly is enclosed in a
            membrane that is basically an
            expansion of the plasma membrane.
Microfilaments (actins filaments)
• Solid rods about 7 nm
  in diameter
• made from actin a
  globular protein, in
  the form of a double
  twisted chain
• Structural role is to
  bear tension, resist
  the pulling forces      Actin subunit

  within the cell                         7 nm
Microfilaments (actins filaments)
                 • Forms a 3-D network
                   called the cortex just
                   inside the plasma
                   membrane to help
                   support the cell’s
                 • make up the core of
                   microvilli of intestinal
Microfilaments (actins filaments)
• Microfilaments are known to assist in cell
  – In muscles cells thousands of actin filaments
    are arranged parallel to one another along the
    length of a muscle cell, interlinking with
    thicker filaments made of the protein myosin.
    Myosin acts as a motor protein as projections
    walk along the actin filaments.
           Muscle cell

 Actin filament

Myosin filament
   Myosin arm

 (a) Myosin motors in muscle cell contraction
Microfilaments (actins filaments)
                                    – Amoeboid movement
                                      interaction of actin
                                      filaments with myosin
Cortex (outer cytoplasm):             near the cell’s trailing
gel with actin network
                                      end squeezes the
 Extending                            interior fluid forward
                                      into the pseudopodium

        Inner cytoplasm: sol with
        actin subunits
Microfilaments (actins filaments)
• Main functions:
  – Maintenance of cell shape (tension-bearing
  – Changes in the cell shape
  – Muscle contraction
  – Cell motility
     • Myosin
     • Pseudopodia
  – Cytoplasmic streaming
       Intermediate Filaments
                                   • Diameter of 8-12nm,
                                   • As well as
                                     Microfilaments, it is
                                     specialized for
                                     bearing tensions.
                                   • Constructed of
                                     different molecular
Keratin proteins                     subunits belonging to
       Fibrous subunit (keratins
       coiled together)
                                     a family of proteins
                                     whose members
                                     include the keratin
          Intermediate Filaments

• Are more permanent fixtures of cells then microtubules and
   – After cells die intermediate filaments are still found on the cells
• Experiments suggest that intermediate filaments are of greater
  importance in reinforcing the shape of a cell and organelles .
   – Nucleolus is surrounded by intermediate filaments that hold it in place
     within the cell
   – Also makes up the nuclear lamina inside the nuclear envelope
•   AP Biology (7th Edition) by Campbell Reece

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