Electron Transport Chain

electron extraction - potential energy of electron transferred when it moves  

• reduction can move electron completely or change degree of sharing in a covalent bond
• electrons shared equally in C-H bonds because C and H have similar electronegativity
• when glucose forms CO2 and H2O, oxygen atoms attract electrons away from hydrogen/carbon
  • oxygen more electronegative than hydrogen/carbon
  • energy released when electrons move from a less electronegative atom to a more electronegative atom
  • shift of electrons during oxidative respiration releases energy to create ATP
• reducing power - NADH can carry energy of electrons donated to it
  • can pass along electrons and reduce other atoms
  • reduces fatty acid precursors to form fats when ATP is plentiful
• releasing energy in stages is more efficient than releasing it all at once

electron transport chain - stage 4 

• series of membrane-associated proteins
• NADH dehydrogenase - 1st protein to receive an electron
• ubiquinone - carrier that passes electrons to the bc1 complex
• bc1 complex - protein-cytochrome complex acting as a proton pump
• cytochrome c - carrier that passes electrons to cytochrome oxidase complex
• cytochrome oxidase complex - uses 4 electrons to reduce O2 so that it forms 2H2O w/ 4H
• NADH gives electrons to NADH dehydrogenase, FADH2 gives electrons to ubiquinone
• energy from electrons transports protons from the mitochondrial matrix into the intermembrane space
• NADH activates 3 pumps, FADH2 activates 2 pumps

chemiosmosis - process where diffusion force generates energy for ATP 

• protons transported into the intermembrane space try to go back into matrix due to diffusion
• protons (ion) can only enter through ATP synthase, which uses proton gradient as an energy source
• reentry of protons powers the ATP synthase
• theoretical yield - 36 molecules of ATP formed
  • 4 ATP from glycolysis (though 2 used during the process)
  • 30 ATP from NADH (3 per NADH)
  • 4 ATP from FADH2 (2 per FADH2)
  • -2 ATP (to move NADH produced by glycolysis into the mitochondrian)
• actual yield - usually lower than 36
  • some protons able to enter matrix w/o using ATP synthase
  • proton gradient not used exclusively for ATP synthesis
  • about 30 ATP actually created
  • aerobic respiration harvests about 32% of energy in glucose

aerobic respiration regulation - ATP stops respiration through feedback inhibition 

• high concentrations of ADP activates enzymes to stimulate ATP synthesis
• phosphofructokinase - main control point in glycolysis
  • catalyzes conversion of fructose phosphate to fructose biphosphate
  • 1st non-reversible step in glycolysis
  • stimulated by high levels of ADP and citrate
• pyruvate decarboxylase - main control point in Krebs cycle
  • inhibited by high levels of NADH
  • citrate synthetase - catalyzes 1st reaction involving conversion of oxaloacetate and acetyl-CoA into citrate