Ch 7

• Prokaryotic cell


  No nucleus, no organelles, no internal membranes
• Eukaryotic cell


  Nucleus, membrane around organelles, membrane compartments

  
• Cytoplasm


  All cellular contents (including organelles) between the nucleus and the cell membrane

  
• Cytosol


  The semi-fluid portion of the cytoplasm containing dissolved ions and molecules
• Bacterial chromosome


  Circular DNA molecule, proteins condense it into the nucleoid
• Bacterial plasmids


  Small circular pieces of DNA found in the cytoplasm, in addition to the chromosome, provide the cell with an advantage

  
• Nucleus


  Contains the genetic material, site of DNA replication and transcription, directs all cell activity

  
• Nuclear envelope


  Double membrane covered in pore complexes that control movement of molecules in and out of the nucleus
• Nuclear lamina


  Network of protein filaments that supports the shape of the nucleus

  
• Chromosomes


  Contain the genetic information, DNA condensed by wrapping around histone proteins
• Eukaryotic ribosomes


  Complexes of ribosomal RNA and ribosomal proteins that synthesize proteins from amino acid monomers
• Locations of eukaryotic ribosomes

  • Free in cytosol (make proteins for the cytosol)
  • Bound to ER and nuclear envelope (make proteins inserted into membranes, for organelles, or secreted)

  
• Endoplasmic reticulum (ER)


  Network of membrane tubules and sacs called cisternae, continuous with the nuclear envelope
• Rough ER


  Covered with bound ribosomes, site of protein synthesis, contains enzymes for protein modification
• Smooth ER


  No ribosomes, contains enzymes for lipid synthesis, carbohydrate synthesis, and detoxification
• Movement of molecules made in the ER


  Transferred to the Golgi Complex by vesicles

  
• Golgi Complex


  Receives material made in the ER, modifies proteins and lipids, targets proteins to their final destination
• Cis face of Golgi


  Receives vesicles from the ER
• Trans face of Golgi


  Vesicles bud off and are sent to other sites
• Movement through the Golgi

  1. Vesicles combine to form new cisterna at cis face

  2. Each cisterna moves with contents from cis to trans

  3. At trans face, proteins are sorted and vesicles bud off to carry them to final destination
• Lysosomes


  Membrane-bound sacs containing hydrolytic enzymes that catalyze digestion, maintain an acidic internal environment
• Phagocytosis


  Lysosomes fuse with food vacuoles to digest foreign material, monomers are absorbed into the cytosol
• Autophagy


  Damaged organelles are surrounded by membrane and fused with lysosomes to break down components, recycling monomers
• Vacuoles


  Large membrane-bound compartments with many functions like storage, waste disposal, and water regulation
• Endomembrane system


  Organelles that work together to synthesize, transport, and export proteins and lipids, connected by continuous membrane or vesicle transfer
• Mitochondria


  Not part of endomembrane system, site of cellular respiration, double membrane with enzymes for ATP synthesis on inner membrane

  
• Chloroplasts


  Not part of endomembrane system, site of photosynthesis, three membranes with enzymes, ribosomes, and DNA in the stroma

  
• Structural similarities between mitochondria and chloroplasts

  • Double membrane
  • Contain their own DNA
  • Contain their own ribosomes
  • Involved in metabolism

  
• Endomembrane system origin


  Proposed to have formed from infolding of cell membrane
• Endosymbiotic theory


  Explains origin of mitochondria and chloroplasts - a small prokaryote was engulfed and began living within a larger cell, developing a mutually beneficial relationship

  
• Evidence for endosymbiotic theory

  • Mitochondria and chloroplasts replicate by binary fission, not mitosis
  • Have double membranes like living bacteria
  • Contain their own DNA
  • Contain their own ribosomes similar to prokaryotes

  
• All eukaryotes have mitochondria, but only plants have chloroplasts, so endosymbiosis happened twice

  
• Smooth ER is involved in lipid metabolism and detoxification reactions.
• Rough ER has ribosomes attached to it, while smooth ER does not.
• The endoplasmic reticulum is continuous with the nuclear envelope