Krebs cycle
A series of chemical reactions at the heart of the mitochondria that completes the breakdown of nutrients to produce cellular energy (ATP), a central crossroads of metabolism.
The Krebs cycle (or citric acid cycle) is the hub of energy metabolism. It takes place in the mitochondria and recovers the energy from broken-down carbohydrates, fats and proteins, converting it into molecules (NADH, FADH2) that then fuel the massive production of ATP.
An original angle (the universal crossroads): what makes the Krebs cycle fascinating is that it is the meeting point of ALL fuels
- Carbohydrates (via pyruvate)
- Fats (via beta-oxidation → acetyl-CoA)
- Proteins (via various amino acids)
Everything ends up entering this single cycle. That is why people say that “fats burn in the flame of carbohydrates”: without a minimum of intermediates supplied by carbohydrates, fat oxidation runs at a crawl.
Practical relevance:
- Several B vitamins (B1, B2, B3, B5) are essential cofactors of the cycle: a deficiency slows down all energy production, hence the fatigue. This is the concrete link between “lack of B vitamins” and “lack of energy”
- Magnesium is also required (activation of ATP)
- In ketosis, ketones also feed the cycle, allowing the body to produce energy without carbohydrates
The Krebs cycle illustrates why a diet lacking in micronutrients (B vitamins, magnesium) causes fatigue even with enough calories: the “cogs” needed to convert the energy are missing.