Mitochondria

• Mitochondria is referred to as the PowerHouse of the cell
• Mitochondria is a sausage-shaped organelle inside the cell
• Structural components of mitochondria:

  • Outer membrane: highly permeable, allows things to move in and out
  • Inner membrane: less permeable, has selective proteins Transporters
  • Inter membrane space: rich in proton ions
  • Cristae: invaginations of the inner membrane, increase surface area for metabolic reactions
  • Mitochondrial Matrix: contains mitochondrial DNA and ribosomes
• Mitochondria produce ATP molecules through cellular respiration
• Cells that need more energy have more mitochondria
• Mitochondria accept unfolded proteins from the nucleus, fold them properly, and activate them for metabolic reactions
• Functions of the mitochondrial membranes:

  • Protein transport:
  • Unfolded proteins from the nucleus are transported into the mitochondria
  • Outer membrane translocase (TOM) and inner membrane translocase (TIM) facilitate protein transport
  • Miscellaneous transport:
  • Ions and small macromolecules move across the mitochondrial membrane for metabolic reactions
• Electron transport chain:

  • Found primarily on the inner membrane
  • Complexes I-IV and ATP synthase are involved
  • High-energy electron Transporters (FADH2 and NADH) carry electrons
  • Electrons are passed down the chain, pumping protons into the inter membrane space
  • Protons move through ATP synthase, creating energy to produce ATP
  • ATP production via the electron transport chain is called oxidative phosphorylation
  • Side effect: formation of reactive oxygen species like hydrogen peroxide and superoxide free radicals
• Mitochondria have two membranes: outer membrane is highly permeable, inner membrane is less permeable
• Mitochondria allow for the transport of various substances such as carbohydrates, amino acids, and fatty acids for metabolic reactions
• Unfolded proteins made in the nucleus by ribosomes in the cytoplasm are transported into the mitochondria for their functions
• Electron transport chain is located specifically on the inner membrane of the mitochondria
• Electron transport chain takes high-energy electrons from NADHs and FADH2s, generated from metabolic reactions, and passes them down the chain to pump protons into the intermembrane space, leading to ATP production via oxidative phosphorylation
• Reactive oxygen species can be produced as an unfortunate side reaction of the electron transport chain
• Metabolic reactions in the mitochondrial Matrix include:
• Conversion of pyruvate into acetyl-CoA
• Krebs cycle
• Beta oxidation of fatty acids
• Urea cycle
• Gluconeogenesis
• Synthesis of heme from Krebs cycle intermediates
• HUG (Heme synthesis, Urea cycle, Gluconeogenesis) reactions occur in both the mitochondria and cytoplasm
• Mitochondria can be involved in apoptosis, where cytochrome C leaks out of the mitochondrial Matrix, activating caspases and leading to programmed cell death
• Mitochondrial DNA can replicate for mitochondrial division or undergo transcription to produce RNA, which combines with ribosomes (70s ribosomes) in the mitochondria to synthesize proteins
• Mitochondrial proteins account for about 15% of the proteins needed for mitochondrial functions, with the remaining 85% coming from nuclear DNA and RNA