The Cytoskeleton                                Microfilaments
• A networked mesh of protein rods that                    ...
Cellular Extensions: Flagella                      Cellular Extensions: Microvilli

               • Sperm cells are the
 ...
The Cell Cycle                                     Interphase
                                                            ...
Protein Synthesis                  Transcription
                                          • Synthesis of
        • DNA pr...
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Chapter3c

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Chapter3c

  1. 1. The Cytoskeleton Microfilaments • A networked mesh of protein rods that • Thin (but dense), support the cell, acting as scaffolding cross-linked strands • Also contain contractile units that allow for the of actin (contractile movement of cells and for intracellular proteins) movement (organelle movement, vesicular • Involved in cell transport) motility and changes • Three Types: in shape – Microtubules – Microfilaments – Intermediate filaments 1 2 Intermediate Filaments Microtubules • Tough, stable, • Long, hollow tubes permanent, rope-like composed of tubulin. protein fibers Large in diameter • Have high tensile • Radiate from the strength centrosome • Helps cells resist • Determine cell shape mechanical stress and organelle and are found in distribution desmosomes for cell- • Important in cell contact 3 intracellular transport 4 Centrosome & Centrioles Cellular Extensions: Cilia • “microtubule organizing center” • Composed of two centrioles (90o to each other) and a granular matrix • Matrix generates microtubules • Centrioles generate spindle fibers during cell 5 6 division 1
  2. 2. Cellular Extensions: Flagella Cellular Extensions: Microvilli • Sperm cells are the only cells in the human body with flagella • Similar to cilia but are longer and allow cells to propel themselves • Finger-like plasma membrane projections • Use a whip-like • Increases plasma membrane surface area motion for locomotion • Typically found in absorptive cells 7 • Example: Lining of the small intestine 8 The Nucleus The Nuclear Envelope • The “control center” of • Double membrane barrier the cell containing separated by a fluid-filled space genetic information • Outer membrane is continuous with RER & is studded with • The largest organelle of ribosomes the cell and is filled with • Inner membrane is lined with nucleoplasm nuclear lamina • Two membranes come together • Composed of: Nuclear and form nuclear pores (entry and envelope, Nucleolus, exit point of particles) and Chromatin 9 10 Nucleoli Chromatin • Loosely coiled DNA fibers • Small, dense body and histone proteins, composed of RNA and condense to form protein, where chromosomes. ribosomes are • DNA + histone = synthesized nucleosome • Condense into chromosomes during cell 11 division 12 2
  3. 3. The Cell Cycle Interphase • Cell growth and DNA • Cell cycles form a multi- replication, “preparation celled organism from one period” original cell • A series of changes cells go • G1 Phase: Growth Phase through from the time they 1, structures are are formed until they divide duplicated • Promote growth and tissue • S Phase: Synthesis repair in organisms Phase, DNA is replicated • Involves phases and • G2 Phase: Growth Phase checkpoints for quality 2, more structural control duplication, final 13 *Movie time! preparations 14 DNA Replication Mitosis • Division of the nucleus: – Prophase – Metaphase – Anaphase – Telophase • Cytokinesis: Division of the cytoplasm • Occurs before cell division • Exceptions: RBCs, nervous, skeletal & • DNA is uncoiled & H-bonds broken by a helicase cardiac tissue • DNA polymerase introduces complementary bases • Replicated DNA is semi-conservative 15 16 • DNA condenses after replication Mitosis Mitosis 17 18 3
  4. 4. Protein Synthesis Transcription • Synthesis of • DNA provides the complementary information for mRNA (messenger protein synthesis RNA) • Transcribes the • Two events: code for making – Transcription proteins and – Translation transports it outside the nucleus 19 20 Translation Translation • Every mRNA codon corresponds to an amino acid • Examples: – CAC = Histidine – CAA = Glutamine – AAA = Lysine 21 22 23 24 4

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