Electron Transport Chain

1
Electron Transport Chain

• Takes place in the cristae of mitochondrium
• Electron acceptors are embedded in the cristae
• Begins with electron from NADH
• Reduces flavoprotein
• Electron is passed to other molecules that have
  higher electronegativity
• Reduces new acceptor and donor is oxidated
• Electron ultimately is accepted by O2 molecule
• Very high electronegativity
• For every 2 NADH molecules O2 is reduce to 2H2O

2
Electron Transport 2

• Each new acceptor requires that the electron be
  at a slightly lower energy state
• Energy is siphoned off of the electrons in small
  increments
• The energy is used by the acceptor molecules to
  change conformation
• All are proteins except Q (ubiquinone) is lipid

3
Close-up of Cristae

• Many electron acceptors used released energy to
  pump an H proton into the intermembrane space
• Gradient of H is formed outside of cristaes

4
Oxidative phosphorylation

• ATP is actually synthesized by enzyme ATP
  synthase
• Many copies embedded in cristae
• Hydrogen gradient needs to reach equilibrium
• H can only pass through ATP synthase molecule
• Passage of H turns molecule like a water wheel
• ATP is generated by enzyme action

5
Net ATP Production

• Glycolysis 2 ATP, Krebs 2 ATP, Electron
  Transport oxidative phosphorylation 34 ATP
• Total of 38 ATP/glucose

6
Fermentation

• Used when oxygen is not available as electron
  acceptor
• Not as efficient as oxidative phosph.
• In humans, only 2 ATP are produced by
  fermentation
• Accumulation of waste molecules
• Sometimes can be used later as energy source
• Type of fermentation is known by waste product

7
Types of Fermentation

• Alcohol fermentation
• Results in ethanol production
• Performed by bacteria and fungi
• Lactic acid fermentation
• Used by animals
• Results in lactate formation
• Causes muscles to ache after workout
• Anaerobic conditions

8
Why Fermentation

• 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

9
Macromolecules and Respiration

• Many types of macromolecules can be used as a
  source for respiration
• Fats and proteins are important
• They enter pathway at various point

10
Regulation of Respiration

• Very complex regulation
• Feedback inhibition of ATP or Citrate can stop
  early stages of reactions
• Allows cell to produce ATP when needed