After glycolysis and the Krebs cycle, 10 NADHs and 2 FADH2s are used in the electron transport chain (ETC) to generate ATP.
Operates in the mitochondria matrix.
Some details of ETC are still under research.
NADH vs FADH2
NADH: Indirectly responsible for producing 3 ATPs each.
FADH2: Produces 2 ATPs each due to lower energy state of electrons.
Oxidation and Reduction
NADH Oxidation:
NADH loses electrons to form NAD+, a proton (H+), and two electrons.
Reaction: NADH → NAD+ + H+ + 2e⁻
Reduction of Oxygen to Water:
Electrons combine with oxygen and protons to form water.
Reaction: O + 2e⁻ + 2H⁺ → H2O
Electron Transport and Energy Release
Electrons move through a series of molecules (e.g., Coenzyme Q, Cytochrome C) in the ETC.
Each transfer releases energy, used to pump protons across the mitochondrial inner membrane (cristae).
Mitochondrial Structure
Inner Membrane (Cristae): Site of ATP synthesis.
Outer Membrane & Matrix: Described in previous lectures.
Proton Gradient and ATP Synthesis
Energy from electron transfers is used by protein complexes to pump protons into the space between the inner and outer mitochondrial membranes, creating a proton gradient.
This gradient is crucial for ATP production.
ATP Synthase
Protons flow back into the matrix through ATP synthase, a protein complex.
The flow of protons spins parts of ATP synthase, facilitating the combination of ADP and inorganic phosphate to form ATP.
ATP Yield
From NADH: 3 ATP per NADH.
From FADH2: 2 ATP per FADH2.
From Glycolysis and Krebs Cycle: Direct yield of 4 ATP.
Total ATP from one molecule of glucose is theoretically 38 ATP.
Conclusion
The electron transport chain involves electron transfer and energy release for ATP synthesis.
Both NADH and FADH2 contribute to the proton gradient needed for ATP production.
Understanding is key for grasping cellular respiration as a whole.