what happens inside the mitochondrion
Inside the mitochondrion, glucose “fuel” is broken down the rest of the way to make lots of usable energy in the form of ATP, mainly through the Krebs (citric acid) cycle and the electron transport chain.
Inside the mitochondrion: the big picture
- The mitochondrion is often called the powerhouse of the cell because it converts the energy stored in food molecules into ATP, the cell’s main energy currency.
- This energy conversion mostly happens in two linked stages: the citric acid (Krebs) cycle in the matrix and oxidative phosphorylation (electron transport chain plus ATP synthase) in the inner membrane.
The spaces and structures
- Mitochondria have an outer membrane, an inner membrane that folds into cristae, and a central fluid-filled region called the matrix.
- The folds (cristae) greatly increase the inner membrane’s surface area, allowing more electron transport proteins and ATP synthase to pack in and make more ATP.
What actually happens to food
- Glucose is first broken into pyruvate in the cytoplasm; pyruvate then enters the mitochondrial matrix, where it is converted into acetyl‑CoA and fed into the citric acid (Krebs) cycle.
- In the Krebs cycle, acetyl‑CoA is stepwise oxidized, releasing carbon dioxide and generating high‑energy carriers like NADH and FADH₂, plus a small amount of ATP.
Electron transport and ATP making
- NADH and FADH₂ donate electrons to the electron transport chain proteins embedded in the inner membrane, which move electrons along and use their energy to pump protons (H⁺) from the matrix to the intermembrane space.
- The stored energy in this proton gradient then drives protons back into the matrix through ATP synthase, which spins to make large amounts of ATP from ADP and phosphate; oxygen acts as the final electron acceptor, forming water.
Other jobs inside mitochondria
- Besides making ATP, mitochondria house their own DNA and ribosomes in the matrix, which allow them to make some of their own proteins and divide somewhat independently of the cell.
- They also participate in cell‑signaling and cell‑death pathways and help regulate metabolism, showing they are more than just an energy converter.
TL;DR: Inside the mitochondrion, pyruvate is fed into the Krebs cycle to generate NADH and FADH₂, whose electrons power the inner‑membrane electron transport chain and proton pumping, and the resulting gradient drives ATP synthase to make most of the cell’s ATP, with CO₂ and water as by‑products.
Information gathered from public forums or data available on the internet and portrayed here.