Warburg, Otto Heinrich

German biochemist who was awarded a Nobel Prize for Physiology or Medicine in 1931 for the discovery of respiratory enzymes that enable cells to process oxygen. In 1923 he devised a manometer (pressure gauge) sensitive enough to measure oxygen uptake of respiring tissue. By measuring the rate at which cells absorb oxygen under differing conditions, he was able to show that enzymes called cytochromes enable cells to process oxygen.

Later he discovered the mechanism of the conversion of light energy to chemical energy that occurs in photosynthesis. He also demonstrated that cancerous cells absorb less oxygen than normal cells.