15/11/2025
How your body moves electrons from food to energy
This figure explains how the human body acts like an electrical circuit—moving electrons extracted from food all the way to oxygen to generate energy. Every meal you eat feeds an invisible current that powers your cells through a continuous flow of electrons inside the mitochondria.
1️⃣ Food as an electron source
Carbohydrates, fats, and proteins are broken down into molecules like glucose and fatty acids that release electrons during oxidation. These electrons are captured by carrier molecules such as NAD⁺ and FAD.
🟢 Example: One molecule of glucose donates enough electrons through NADH and FADH₂ to drive the production of about 30 ATP molecules.
2️⃣ Electron delivery to mitochondria
Nutrients are converted into acetyl-CoA, which enters the TCA cycle in mitochondria. Each turn of the cycle generates high-energy electron carriers that feed into the electron transport chain.
🟢 Example: When oxygen is limited, cells divert pyruvate to lactate to keep glycolysis running and prevent a bottleneck in electron flow.
3️⃣ The electron transport chain
Electrons move through a series of protein complexes embedded in the inner mitochondrial membrane. As they flow, energy is released to pump protons across the membrane, creating an electrochemical gradient.
🟢 Example: This “proton motive force” is the voltage that powers ATP synthase, the enzyme that produces ATP from ADP and phosphate.
4️⃣ Oxygen as the final electron acceptor
At the end of the chain, oxygen captures electrons and forms water, completing the circuit. Continuous oxygen flow keeps the system balanced and prevents electron buildup.
🟢 Example: When oxygen supply drops, excess electrons can leak, generating reactive oxygen species that damage cells.
5️⃣ ATP as usable energy
The proton gradient drives ATP synthase to generate ATP, the chemical energy currency used for everything from muscle contraction to DNA repair.
🟢 Example: Tissues with high energy demand, such as the brain and heart, contain dense mitochondrial networks to maximize electron throughput.
In essence, metabolism is electricity at the molecular level. Food provides the electrons, mitochondria manage their flow, and oxygen completes the circuit—turning chemical energy into the electrical current that sustains life.
