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Oxidative Phosphorylation 1 definitions

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  • Quinone
    Lipid-soluble molecule with an isoprene chain, diffuses within the membrane and carries two electrons between protein complexes.
  • Cytochrome
    Protein containing a porphyrin ring with central iron, capable of carrying one electron; targeted by poisons like cyanide.
  • Iron-Sulfur Protein
    Protein with iron complexed by cysteine and sulfur, able to carry one to four electrons depending on iron content.
  • Complex I
    First protein complex in the mitochondrial membrane where NADH donates electrons, leading to proton pumping.
  • Complex II
    Protein complex where FADH2 donates electrons; contains FAD as a tightly bound cofactor and pumps fewer protons.
  • Ubiquinone
    Specific quinone that transfers electrons from complexes I or II to complex III within the mitochondrial membrane.
  • Complex III
    Protein complex receiving electrons from ubiquinone, involving cytochrome B and iron-sulfur proteins.
  • Cytochrome c
    Protein located on the intermembrane space side, shuttles electrons from complex III to complex IV.
  • Complex IV
    Final protein complex where cytochrome a transfers electrons to oxygen, resulting in water formation.
  • NADH
    Electron donor that initiates transport at complex I, leading to greater proton pumping and higher ATP yield.
  • FADH2
    Electron donor entering at complex II, resulting in fewer protons pumped and lower ATP yield compared to NADH.
  • Protonmotive Force
    Gradient created by proton pumping across the mitochondrial membrane, essential for ATP synthesis.
  • Intermembrane Space
    Region between mitochondrial membranes where protons accumulate during electron transport.
  • Matrix
    Innermost compartment of the mitochondrion, source of protons and site of NADH and FADH2 formation.
  • Chemiosmotic Theory
    Concept explaining ATP synthesis via membrane-associated electron transport and proton gradient formation.