Unit 5

• Mitochondria


  In almost all eukaryotic cells. Bound by 2 membranes which makes 5 functional spaces
• ATP production in mitochondria

  Oxidative phosphorylation
• Mitochondria


  • Efficient means of ATP generation
• Chloroplasts


  In plants and green algae
• ATP production in chloroplasts

  Photosynthesis
• Mitochondria and chloroplasts


  • Both have mechanisms for harnessing energy
• Chemiosmotic coupling


  High-energy electrons are transferred through a series of membrane embedded protein complexes
• Electron transport chain


  Formed from high-energy electrons getting transferred through protein complexes embedded in the membrane
• Electrochemical gradient


  The change in pH and membrane potential, formed from H+ being pumped across the membrane by energy from electron transfer
• Chemiosmotic coupling part 2

  ATP synthase pumps protons back across the electrochemical gradient
• ATP synthase


  Converts ADP and inorganic phosphate into ATP
• Mitochondria


  • Dynamic organelles constantly changing, dividing, fusing
• Dynamin


  A large GTPase, uses energy from GTP hydrolysis
• Rhodamine 123 can also be used to stain mitochondria, can do live cell imaging where you stain mitochondria, then stain microtubules, then visualize the overlap
• Five Functional Spaces in Mitochondria

  1. Matrix 2. Inner membrane 3. Outermembrane 4. Intermediate space 5. Cristae
• Matrix

  Metabolic enzymes, oxidation of foodstuffs
• Inner Membrane (IMM)

  machinery for OXPHOS, metabolite transporters, TIMS, also generates crista space. Diffusion barrier to ions and small molecules
• Outer Membrane (OMM)


  Lots of porin, no gradient across the OMM, Toms, pro-apoptotic proteins. Permeable to ions and molecules up to 5kDa
• Intermembrane Space (IMS)


  Equivalent to cytosine (some pH & ion composition, no electrochemical gradient)
• Cristae


  Membrane disks that protrude deeply into the matrix, the interior is the Cristal space. Crista membrane is contiguous with the IMM
• Inner boundary membrane


  Where the IMM runs parallel to the OMM
• Oxidative Phosphorylation

  Electron transfer steps proceed from the compounds with a large negative redox potential. Energy of electron decrease as they are passed along the chain, but electron affinity increases.
• 3 H+ Pumping Complexes

  1. Complex I, passes electrons to CoQ
  2. Complex III, accepts electrons from CoQ, passes electrons to CytC
  3. Complex IV, terminal electron acceptor, from Cytc, binds molecular O2.
• Complex II

  Doesn’t pump H+, but still a ETC complex
• Cardolipin


  Supports membrane curvature in cristae. Made in mito membranes
• Respiratory control

  Uncoupling agents disconnect electron transfer from ATP production
• Nuclear DNa

  Transcribed, translated, and imported via TOMs and TIMs as discussed
• mtDNA 


  Expressed in mitochondrion itself, all protein machinery for transcription and translation is nuclear encoded
• Heteroplasmy


  Mixed mtDNA populations in a mitochondrion/cell. Caused by random segregation.
• Threshold Effects


  When a given mutant load does not exact the same phenotypic consequences on different tissues. This gives rise to diseases