ETC 2

• Regulation of ATP synthesis

  Regulation of aerobic respiration is by feedback inhibition

  
• Examples of feedback inhibition

  • Glycolysis inhibited by ATP and by citrate
  • Pyruvate dehydrogenase inhibited by NADH
  • Citrate synthase inhibited by ATP
  • The availability of ADP
• Regulation of cellular respiration

  Governed primarily by the need for ATP

  
• [ADP] controls the rate of O2 consumption

  Electrons do not flow through the ETC towards O2 unless ADP is simultaneously phosphorylated to ATP
• Electrons do not flow from fuel molecules to O2

  Unless ATP needs to be synthesized
• High [ADP] or low [ATP]/[ADP]

  Drives oxidative phosphorylation
• Conditions limiting the rate of respiration

  • State 1: Availability of ADP and substrate
  • State 2: Availability of substrate only
  • State 3: The capacity of the respiratory chain itself, when all substrates and components are present in saturating amounts
  • State 4: Availability of ADP only
  • State 5: Availability of oxygen only

  
• Inhibitors of oxidative phosphorylation

  • Inhibitors of respiratory chain components
  • Inhibitors of oxidative phosphorylation
  • Uncouplers of oxidative phosphorylation
• Inhibitors of the respiratory chain

  • Bind to different components of the electron transport chain
  • Does not allow to change in a reversible form from an oxidized state to a reduced state
  • Results in the accumulation of reduced forms prior to the inhibitor point, and oxidized forms of the components of the ETC down the line of inhibition point
• Inhibitors of the ETC

  • Rotenone
  • Piericidin A
  • Antimycins
  • Cyanide
  • Carbon monoxide
  • Azide
• Inhibitors of ATP synthase

  • Oligomycin
  • Dicyclo hexyl carbo diimide (DCCD)
• Uncouplers


  • In damaged mitochondria, respiration (i.e., electron transport) may occur unaccompanied by oxidative phosphorylation
  • When this happens the mitochondria are said to be uncoupled
  • In the presence of an uncoupling agent, respiration is increased, but ATP is not formed and the energy created is released as heat
  • Symptoms due to uncoupling in vivo include increased respiration and temperature, rapid onset of rigor mortis, and liver damage due to mitochondrial toxicity

  
• Uncoupler


  • Dinitrophenol