Topic 2

• Key eukaryotic cell organelles

  • Nucleus
  • Endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Mitochondria
  • Ribosomes
  • Vacuole
  • Chloroplasts
  • Cell wall
  • Plasma membrane
• Nucleus


  Where DNA replication occurs and mRNA is made, contains the genetic code
• Nucleolus


  Site of rRNA production and ribosome assembly
• Rough endoplasmic reticulum (RER)


  Site of protein synthesis due to ribosomes on the outside
• Smooth endoplasmic reticulum (SER)

  Site of lipid and carbohydrate synthesis and storage
• Golgi apparatus


  Modifies, packages and distributes molecules like glycoproteins, secretory enzymes, carbohydrates, lipids
• Lysosomes


  Bags of digestive enzymes involved in phagocytosis and exocytosis
• Mitochondria


  Site of aerobic respiration and ATP production
• Ribosomes


  Site of protein synthesis, found in both prokaryotic and eukaryotic cells
• Vacuole


  Fluid-filled structure that provides support and stores substances in plant cells
• Chloroplasts


  Site of photosynthesis in plant cells
• Cell wall


  Provides structural strength and prevents bursting in plant and fungal cells
• Plasma membrane


  Controls what can enter and exit the cell
• Key differences between prokaryotic and eukaryotic cells

  • Prokaryotes are smaller
  • Prokaryotes lack membrane-bound organelles
  • Prokaryotes have circular DNA rather than a nucleus
  • Prokaryotes have 70S ribosomes rather than 80S
  • Prokaryotes may have a cell wall, capsule, and flagella
  • Eukaryotes have membrane-bound organelles like nucleus, mitochondria, chloroplasts
• Viruses


  Acellular and non-living, consist of genetic material, capsid, and attachment proteins, replicate inside host cells
• Methods of studying cells

  • Microscopy (optical and electron)
  • Cell fractionation and ultracentrifugation
• Magnification


  How many times larger the image is compared to the object
• Resolution


  Minimum distance between two objects that can still be viewed as separate
• Cell fractionation


  1. Homogenization to break open cells

  2. Differential centrifugation to isolate organelles by density
• Conditions for cell fractionation: cold, isotonic, buffered
• Order of organelle isolation by density

  • Nuclei
  • Chloroplasts and mitochondria
  • Lysosomes and ER
  • Ribosomes
• Eukaryotic cells divide by mitosis or meiosis, prokaryotes replicate by binary fission, viruses replicate inside host cells
• Cell cycle stages


  Interphase (G1, S, G2)

  Mitosis (Prophase, Metaphase, Anaphase, Telophase)

  Cytokinesis
• Key facts about mitosis: single round of division, genetically identical cells produced, diploid cells
• Host cell


  The cell that uses the genetic material to replicate the virus particle
• Eukaryotic cell cycle


  1. Interphase

  2. Mitosis
• Interphase


  The longest stage of the cell cycle, includes G1, S, and G2
• G1


  Cell increases in size, organelles double
• S phase


  DNA replication happens
• G2


  Further growth, preparation for mitosis, error check stage
• Nuclear division


  Mitosis or meiosis
• Cytokinesis


  Cytoplasm divides to create two new cells
• Mitosis


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Mitosis


  • Only one round of division
  • Genetically identical cells created
  • Cells are diploid (two copies of every chromosome)
  • Used for growth and repair
• Clonal expansion of B cells is an example of growth through mitosis
• Prophase


  1. Chromosomes condense and become visible

  2. Centriole pairs move to opposite poles

  3. Spindle fibers form
• Metaphase


  1. Chromosomes line up along the equator

  2. Spindle fibers attach to centromeres and chromatids
• Anaphase


  1. Spindle fibers retract, pulling chromatids to opposite poles

  2. Chromatids become chromosomes
• Telophase


  1. Chromosomes reach poles, become longer and thinner

  2. Spindle fibers disintegrate

  3. Nucleus reforms
• Mitotic index


  Percentage of cells in a field of view that are in a stage of mitosis