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Cell Organelles _ their Functions

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Cell Organelles _ their Functions Powered By Docstoc
					                                                  Specialized structures within a cell are called

                                                                   organelles
                                                            •   Very small; only observed
                                                                under a microscope
                                                            •   Have specific functions
            Cellular Organelles                             •   Found throughout cytoplasm
             & their Functions




               Plasma membrane
• boundary between the cell and its environment             Plasma membrane
  FUNCTION: controls what
  materials enter and exit the cell
“Selectively permeable”

Structure:
•Phospholipid bilayer
•Proteins
•cholesterol




                                                                                                    1
       Cytoplasm & Cytosol                       Nucleus
 Cytoplasm                          FUNCTION: The control center
 – area between nucleus                  How?
  and plasma membrane
 Cytosol                            • The nucleus contains
 – Jelly-like substance enclosed      chromatin - strands of DNA
   by cell membrane
 – Provides a medium for            • DNA is the instructions for making
   chemical reactions to take         proteins
   place

cytoplasm = cytosol + organelles    • Proteins carry-out the work of the cell




                                         Nucleolus
                                   Disappears when cell divides

                                   FUNCTION: makes ribosomes
 Nuclear
Structure



                                                                   Nuclear pores
                                                                   FUNCTION: Allows
                                                                   materials to exit the
                                                                   nucleus
                                                                         (RNA/ribosome)



                                                                                           2
        Ribosomes
•FUNCTION: protein synthesis
  – Consists of a large subunit and a small subunit
  – No membrane
  – Subunits made in nucleolus
                                                                        Endomembrane System–
                                                                               Nucleus(DNA)
• May be located:                                                              Ribosome
  – BOUND: on the endoplasmic reticulum                                        Rough ER
  – FREE: in the cytoplasm
                                                                             Golgi Apparatus
                                                                                Vesicles




         Endoplasmic Reticulum (ER)
                                                                            Endoplasmic Reticulum
                     Transport system
                                                                                   and ribosomes
    (endoplasm means "within cytoplasm", reticulum means "little net"
Rough ER – contains ribosomes
          which make proteins
          ER modifies them
Smooth ER – no ribosomes;
    produces and stores lipids
              produces Ca+
                detox




                                                                                                    3
          Golgi Apparatus                                                Golgi continued
                “The Post Office”
flattened stacks of membranes
FUNCTION: collection, packaging and distribution
of molecules made in the cell and used elsewhere         • front end (CIS) faces the ER
                                                         • back end (trans) faces the
                Transport                                  cell membrane
                 vesicle
                                                         • unprocessed proteins enter
                                                           the Golgi apparatus, are
                                                           processed, and exit near the
                                                           cell membrane for export




          Golgi Apparatus
        and associated vesicles                                            Lysosomes
                                                           • Small membranous sacs
                                                           • Contain digestive enzymes
                       Vesicles                               FUNCTION: Lysosomes break down cellular
                       are membranous sacs                    materials and worn out cell parts
                       FUNCTION: transport
                       materials into, within, and out
                       of cells




                                                                                                        4
                      Vacuoles
Membranous sacs for storage of materials
      examples: food vacuoles; water vacuoles

    Plant cells have a large central vacuole that          Structure, Support and
    stores water and supports the plants structure          Movement of Cells
    Plant Cell                    Animal Cell




                   Cytoskeleton                                 Types of cytoskeleton
                 network of thin tubes and filaments
                 that provide structural support and   microtubules
                 movement for the cell                                          • Maintain cell shape
                                                                                • Move organelles around
                                                                                • Make up cilia, flagella and centrioles

                                                       intermediate filaments
                                                                                • Maintain shape of cell and nucleus
                                                                                • Anchor organelles
Three Types:
                                                       microfilaments
  Microfilaments                                                                • Muscle contraction
                                                                                • Movement of cytoplasm
     Intermediate                                                               • Cell division
     Filaments                        Microtubules




                                                                                                                           5
           Centrioles
• FUNCTION: move                              Movement                    Cilia - numerous short hairs
  chromosomes during cell
                                                                          move materials across the cell’s surface
  division
• located just outside nucleus           Flagella - long whip-like        “row” protists through water

                                         Propel cell in a snake-like fashion




                Cell Wall
  – rigid structure outside the plasma
    membrane for support                                        Central vacuole
     – ONLY in plants, fungi, bacteria                                                  ONLY in plants
                                                                                        Stores water and
                                                                                        other materials
                                                                                        Can be up to 90%
                                                                                        of the cells
                                                                                        volume
                                                                                        Turgor pressure
                                                                                        provides support




                                                                                                                     6
              Energy-Related                                          Chloroplasts
                                                                      in plant cells ONLY
                Organelles:                         Site of photosynthesis
                                                    converts energy from the sun into food for the plant

                Mitochondria &                      has a double membrane and its own DNA & ribosomes

                 Chloroplasts




                   Mitochondria
                 Site of cellular respiration

Converts food into a form of energy
usable to the cell
has a double membrane and its own DNA & ribosomes


                     ATP




                                                                                                           7

				
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