3a; cellular respiration
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3a; cellular respiration

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3a; cellular respiration 3a; cellular respiration Presentation Transcript

  • Lecture 3a: Cellular Respiration Cellular Respiration
  • Cellular Respiration
    • This is the reason you breathe
    • How cells make ATP from carbohydrates
    • Essentially the reverse of photosynthesis
  • Helper molecules
    • Coenzymes: nonprotein helpers that move electrons and H around
    • NAD + and FAD + become NADH and FADH
  • 4 Phases
    • Glycolysis: Occurs in cytoplasm
      • Produces 2 ATP and NADH
      • Breaks glucose in half into 2 pyruvate
    • Prep reaction: Occurs in matrix
      • Produces NADH
      • Breaks pyruvate into 2-carbon acetyl group
      • Releases CO 2
  • 4 Phases
    • Citric acid cycle: occurs in matrix
      • Produces more NADH and FADH 2
      • Releases CO 2
      • Produces 2 ATP
    • Electron transport chain: Occurs in crista
      • NADH and FADH 2 release electrons
      • Energy released
      • Produces water
  • Glycolysis
    • Occurs outside the mitochondria
    • Uses 2 ATP, but makes 4, so total gain of 2 ATP per glucose broken
    • Makes 2 pyruvate from 1 glucose
  • Preparatory Reaction
    • Occurs in matrix of mitochondria
    • Each pyruvate is broken into CO 2 and C 2 acetyl group, which binds to coenzyme A to produce acetyl CoA
    • NADH is produced
  • Citric Acid Cycle
    • Occurs in matrix of mitochondria
    • Acetyl CoA is oxidized to CO2
    • NADH and FADH2 are produced
    • ATP is produced
  • Electron transport chain
    • Occurs in cristae of mitochondria
    • Series of carriers that pass electrons from one to the next
    • NADH and FADH2 are the sources of the electrons, but the chain does not accept the H + , only the e-
    • Final acceptor for electrons is the O 2 that we breathe in!
  • Electron transport chain
    • Energy released as electrons move down the chain is used to make ATPs
    • NAD and FAD are recycled to be used again
  • Electron transport chain
    • What about the H + ?
    • The energy released by the ETC is used to pump H + into the inter-membrane space, between inner and outer membranes of mitochondria
    • This creates a gradient- more H + in inter-membrane space than in matrix
  • Electron transport chain
    • Like in photosynthesis, this gradient results in potential energy that can be used
    • ATP synthase exists in cristae
    • H + flows back into matrix through synthase, which makes ATP from the energy
  • Electron transport chain
    • Produces 34 ATP from each glucose that originally entered the cycle
    • ETC ATP plus ATP made earlier= 38 ATP per glucose
    • This is about 40% of energy in glucose, the rest is lost as heat
  • Fermentation
    • Cellular respiration requires O 2 as the final acceptor in the electron transport chain, but what if no O 2 is available?
    • Pyruvate is reduced to make lactate, H + comes from NADH
    • Only makes 2 ATP- what is the point?
  • Fermentation
    • Regeneration of NAD keeps glycolysis going, instead of stalling (=death)
    • Can create short bursts of energy
    • Why you are sore after strenuous work
    • Yeasts use fermentation and generate ethyl alcohol instead of lactate