Who won the 1961 Nobel Prize in Chemistry for discovering the carbon fixation cycle?

Melvin Calvin won the 1961 Nobel Prize in Chemistry for research on carbon dioxide assimilation in plants, work that revealed the cycle now commonly called the Calvin cycle.

Calvin led a research program at the University of California, Berkeley, where scientists used radioactive carbon-14 to trace carbon dioxide through photosynthetic reactions. Andrew Benson and James Bassham were important collaborators, and the fuller name Calvin–Benson–Bassham cycle recognizes their contributions. Nevertheless, the Nobel Prize was awarded to Melvin Calvin alone, making his name the canonical answer to this quiz question.

The team studied green algae such as Chlorella and used rapid sampling and paper chromatography to identify the sequence of compounds formed after carbon dioxide entered photosynthesis. Their work showed that carbon fixation is not a single reaction producing sugar immediately, but a cycle of reactions that regenerates its carbon-dioxide acceptor.

The Nobel citation was “for his research on the carbon dioxide assimilation in plants,” rather than literally “for discovering the carbon fixation cycle.” That wording is a simplified but fair description of the achievement. The cycle uses ATP and NADPH from the light reactions to produce carbohydrate precursors such as glyceraldehyde 3-phosphate.