Cellular Respiration Stage 2

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Cellular Respiration Stage 2 3 Oxidation of
Pyruvate Krebs Cycle
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Glycolysis is only the start

• Glycolysis
• Pyruvate has more energy to yield
• 3 more C to strip off (to oxidize)
• if O2 is available, pyruvate enters mitochondria
• enzymes of Krebs cycle complete the full
  oxidation of sugar to CO2

3C
1C
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Cellular respiration
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Mitochondria  Structure

• Double membrane energy harvesting organelle
• smooth outer membrane
• highly folded inner membrane
• ________________
• ____________________________
• fluid-filled space between membranes
• ____________________________
• inner fluid-filled space
• mitochondrial DNA, ribosomes
• enzymes
• free in matrix membrane-bound

What cells would have a lot of mitochondria?
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Mitochondria Function
Oooooh!Form fits function!
Dividing mitochondria Who else divides like that?
Membrane-bound proteins Enzymes permeases

Advantage of highly folded inner
membrane? ____________________________
____________________________
What does this tell us about the evolution of
eukaryotes? __________________________
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Oxidation of pyruvate

• Pyruvate enters mitochondrial matrix
• 3 step oxidation process
• releases _______ (count the carbons!)
• reduces _______________ (moves e-)
• produces __________________
• Acetyl CoA enters ________________

3C
2C
1C
Wheredoes theCO2 go? Exhale!
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Pyruvate oxidized to Acetyl CoA
reduction
Acetyl CoA
Coenzyme A
CO2
Pyruvate
C-C
C-C-C
oxidation
Yield 2C sugar NADH CO2
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Krebs cycle
1937 1953

• aka Citric Acid Cycle
• in _________________________
• 8 step pathway
• each catalyzed by specific enzyme
• step-wise catabolism of 6C citrate molecule
• Evolved later than glycolysis
• does that make evolutionary sense?
• bacteria ?3.5 billion years ago (glycolysis)
• free O2 ?2.7 billion years ago (photosynthesis)
• eukaryotes ?1.5 billion years ago (aerobic
  respiration organelles ? mitochondria)

Hans Krebs 1900-1981
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Count the carbons!
acetyl CoA
pyruvate
citrate
oxidationof sugars
This happens twice for each glucose molecule
x2
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Count the electron carriers!
acetyl CoA
pyruvate
citrate
______________________________
This happens twice for each glucose molecule
x2
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Whassup?
So we fully oxidized glucose C6H12O6 ? CO2
ended up with 4 ATP!
Whats the point?
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Electron Carriers Hydrogen Carriers

• Krebs cycle produces large quantities of
  _______________
• ____________
• ____________
• go to Electron Transport Chain!

ADP Pi
ATP
Whats so important about electron carriers?
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Energy accounting of Krebs cycle
pyruvate ? ? ? ? ? ? ? ? ? CO2
3C
ATP

• Net gain 2 ATP
• 8 NADH 2 FADH2

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Value of Krebs cycle?

• If the yield is only 2 ATP then how was the Krebs
  cycle an adaptation?
• __________________________________
• ____________________________________
• __________________________________
• __________________________________
• ____________________________________

like in the bank
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Whats thepoint?
The pointis to makeATP!
ATP
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And how do we do that?

• ATP synthase
• set up a H gradient
• allow H to flow through ATP synthase
• powers bonding of Pi to ADP
• ADP Pi ? ATP

ADP
ATP
But Have we done that yet?
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NO!The final chapter to my story is next! Any
Questions?