1. Food Breakdown (Glycolysis and Citric Acid Cycle):
* The process of breaking down food begins with glycolysis, where glucose is broken down into pyruvate.
* Pyruvate then enters the mitochondria, where it is converted to acetyl-CoA.
* Acetyl-CoA enters the citric acid cycle (also known as the Krebs cycle), a series of reactions that further break down the molecule.
2. Electron Carriers: NADH and FADH2:
* Throughout glycolysis and the citric acid cycle, electrons are removed from food molecules.
* These electrons are picked up by electron carrier molecules:
* NAD+ is reduced to NADH
* FAD is reduced to FADH2
* NADH and FADH2 are essentially "energy packages," carrying the potential energy from the food molecules.
3. Electron Transport Chain:
* NADH and FADH2 deliver their electrons to the electron transport chain (ETC) located in the inner mitochondrial membrane.
* The ETC is a series of protein complexes that pass electrons down a chain, releasing energy at each step.
* This energy is used to pump protons (H+) across the membrane, creating a proton gradient.
4. ATP Production:
* The proton gradient created by the ETC is used by ATP synthase, an enzyme that uses the energy to create ATP (adenosine triphosphate), the primary energy currency of the cell.
In Summary:
* The breakdown of food through glycolysis and the citric acid cycle generates high-energy electrons that are captured by NADH and FADH2.
* These electron carriers deliver their electrons to the ETC, where the energy is used to create a proton gradient.
* This gradient drives ATP synthase to produce ATP, which powers various cellular functions.
Key Points:
* The majority of the energy from food is stored in the high-energy electrons carried by NADH and FADH2.
* ATP is the ultimate energy currency of the cell, and its production is directly linked to the electron transport chain and the proton gradient it creates.
