Download Cellular Respiration 2

Cellular Respiration 2
5/26/11
Electron Transport Chain
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Takes place in the cristae of mitochondrium
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Electron acceptors are embedded in the inner membrane of the cristae
Begins with electron from NADH
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Reduces flavoprotein
Electron is passed to other molecules that have higher electronegativity
• Reduces new acceptor
Electron ultimately is accepted by O2 molecule
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Very high electronegativity
For every 2 NADH molecules O2 is reduce to 2H2O
Electron Transport 2
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Each new acceptor requires that the electron be at a slightly lower energy state
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All are proteins except Q (ubiquinone) is lipid
Energy is siphoned off of the electrons in small increments
The energy is used by the acceptor molecules to change conformation
•Change in conformation is often linked to pumping H+ across inner membrane
Close-up of Cristae
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Many electron acceptors used released energy to pump an H+ proton into the intermembrane space
– Gradient of H+ is formed outside of cristaes
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ATP is actually synthesized by enzyme ATP synthase
– Many copies embedded in cristae
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Hydrogen gradient needs to reach equilibrium
– H+ can only pass through ATP synthase molecule
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Passage of H+ turns molecule like a water wheel
Oxidative phosphorylation
ATP is generated by enzyme action
Net ATP Production
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Glycolysis 2 ATP, Krebs 2 ATP, Electron Transport & oxidative phosphorylation 34 ATP
Total of 38 ATP/glucose
Photosynthesis and Respiration
Complementary processes
Plants perform both, heterotrophs only use respiration
Each uses waste product of other process (O2 and CO2)
Fermentation
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Used when oxygen is not available as electron acceptor
Not as efficient as oxidative phosph.
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In humans, only 2 ATP are produced by fermentation
Accumulation of waste molecules
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Sometimes can be used later as energy source
• Type of fermentation is known by waste product
Types of Fermentation
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Alcohol fermentation
– Results in ethanol production
– Performed by bacteria and fungi
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Lactic acid fermentation
– Used by animals
– Results in lactate formation
– Causes muscles to ache after workout
– Anaerobic conditions
Why Fermentation
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Pyruvate is dividing point of two systems
If O2 is available pyruvate enters mitochondrium
If O2 level is low Pyruvate stays in cytosol and undergoes fermentation
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Macromolecules and Respiration
Many types of macromolecules can be used as a source for respiration
– Fats and proteins are important
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They enter pathway at various point
Regulation of Respiration
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Very complex regulation
Feedback inhibition of ATP or Citrate can stop early stages of reactions
Allows cell to produce ATP when needed