- NADH and FADH2 carry electrons to the ETC
- Each become oxidized, losing two electrons to the ETC
The Electron Transport Chain (ETC) Structure
- Located within the inner mitochondrial membrane
- Composed of various protein structures arranged in order of increasing electronegativity
- Ex. weakest electron attractor (NADH dehydrogenase) is at the beginning of the chain and the strongest (cytochrome oxidase) at the end
How it Works:
- Electrons pass from one component protein in the chain to the next
- As they move from molecule to molecule they occupy ever more stable position relative to the nuclei of the atoms they associate with;
- Free energy released in the process is used to move protons [H+ ions] from the mitochondrial matrix to the intermembrane space
- Electrons reaching the end of the chain are in very stable positions and require the extremely electronegative oxygen to remove them from the ETC
- NAD+ and FAD+ are in limited supply and must be oxidized by the ETC to reuse them
- Electrons must be removed from the ETC by oxygen to keep the ETC working
- Drops electrons off at first complex; moves 3 H+ ions; produces 3 ATP
- GLYCOLYSIS: NADH cannot penetrate the mitochondrial inner membrane, however a membrane shuttle transfers electrons from the glycolysis NADH to FAD to produce FADH2
- Drops electrons off at cytochrome Q; moves 2 H+ ions; produces 2 ATP
Chemiosmosis and Oxidative ATP Synthesis
- The intermembrane space is impermeable to H+ ions
- Pumping H+ ions out of the matrix and into them intermembrane space creates an electrochemical gradient
- Electron free energy is transferred to potential energy in the electrochemical gradient
- Higher positive charge [H+ ions] in the intermembrane space than in the matrix
- Higher concentration of H+ ions in the intermembrane space than in the matrix
Proton-Motive Force (PMF):
- Created by the H+ ions desire to move away from each other because they repel one another (like charges) and the want to diffuse into the matrix (low H+ conc.)
- Causes H+ ions to move around in the intermembrane space
- Unable to move through the inner membrane, H+ ions are forced to move through special protein channels called ATP synthase
- Free energy of the electrochemical gradient drives the synthesis of ATP from ADP and Pi in the matrix; chemiosmosis
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