One repeating loop of reactions explains how almost every cell burns fuel for energy

In 1937, Hans Krebs worked out the circular sequence of chemical reactions that breaks down sugars and fats to release usable energy inside cells, regenerating its own starting molecule each turn. The citric acid cycle turned out to be nearly universal across aerobic life. Krebs shared the 1953 Nobel Prize in Physiology or Medicine for it.

— Hans Krebs, The Citric Acid Cycle — Enzymologia, 1937; Nobel Prize in Physiology or Medicine, 1953