Oxidative Phosphorylation Flashcards

Oxidative Phosphorylation

Overview

  • Oxidative phosphorylation involves the electron transport chain and chemiosmosis.
  • Electrons are donated by carriers NADH and FADH2.
  • Electrons move towards more electronegative partners within the inner mitochondrial membrane, losing energy as they progress.
  • This released energy is used to pump H+ ions, ultimately leading to ATP production.
  • Oxygen is the final electron acceptor.

The Electron Transport Chain

  • Oxidative phosphorylation consists of the electron transport chain and chemiosmosis.
  • The electron transport chain includes several complexes (I-IV), each containing multiple proteins with electron carriers.
  • NADH donates electrons at Complex I, while FADH2 donates electrons at Complex II.
  • Ubiquinone (Q) and cytochrome c (Cyt c) facilitate electron transfer between complexes within the inner membrane.
  • Complexes I, III, and IV pump H+ from the mitochondrial matrix into the intermembrane space, using the energy released by electron transfer.

Redox Potential and Electron Flow

  • Redox partners are arranged in order of increasing electronegativity.
  • NADH has the lowest electronegativity and donates electrons at Complex I, which are then passed down the chain of increasingly electronegative partners.
  • Electrons ultimately reduce O2 (the final electron acceptor) to form H2O.
  • NAD+ and FAD are replenished to continue accepting electrons during glycolysis and the citric acid cycle.

Chemiosmosis and ATP Synthase

  • The pumping of H+ creates an electrochemical gradient across the inner mitochondrial membrane.
  • This gradient represents potential energy, similar to water stored behind a dam.
  • H+ ions flow down their concentration gradient through ATP synthase, powering its rotor and enabling the phosphorylation of ADP + Pi into ATP.

ATP Synthase

  • ATP synthase is a molecular machine that uses the proton gradient to synthesize ATP.

Proton-Motive Force

  • The proton gradient (proton-motive force) can be utilized for other cellular processes.
  • Examples include flagellar rotation in bacteria and import/export of molecules across the inner membrane.

ATP Yield

  • 1 NADH yields approximately 2.5 ATP.
  • 1 FADH2 yields approximately 1.5 ATP.
  • 1 Glucose molecule yields about 30 ATP.
  • Approximately 34% of the energy contained in glucose is harvested and converted into ATP, with the remainder dissipated as heat.