3a; cellular respiration

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  • 1.Lecture 3a: Cellular Respiration Cellular Respiration

2. Cellular Respiration

  • This is the reason you breathe
  • How cells make ATP from carbohydrates
  • Essentially the reverse of photosynthesis

3. Helper molecules

  • Coenzymes: nonprotein helpers that move electrons and H around
  • NAD +and FAD +become NADH and FADH

4. 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

5. 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 2release electrons
    • Energy released
    • Produces water

6. 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

7. Preparatory Reaction

  • Occurs in matrix of mitochondria
  • Each pyruvate is broken into CO 2and C 2acetyl group, which binds to coenzyme A to produce acetyl CoA
  • NADH is produced

8. Citric Acid Cycle

  • Occurs in matrix of mitochondria
  • Acetyl CoA is oxidized to CO2
  • NADH and FADH2 are produced
  • ATP is produced

9. 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 2that we breathe in!

10. 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

11. 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

12. 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

13. 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

14. Fermentation

  • Cellular respiration requires O 2as the final acceptor in the electron transport chain, but what if no O 2is available?
  • Pyruvate is reduced to make lactate, H +comes from NADH
  • Only makes 2 ATP- what is the point?

15. 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