1946 Photosynthesis

The book of science

Tom Sharp

Melvin Calvin botany Photosynthesis


Working at the Lawrence Radiation Laboratory, Melvin Calvin had a ready supply of the radioactive isotope carbon-14. So he fed it to alga in flasks and stopped the reactions every few seconds to test how the carbon was taken up by the alga into an increasing set of compounds, thus letting him describe the cycle of reactions in the stroma of chloroplasts of plants synthesizing energy from sunlight.


From sunlight plants make adenosine triphosphate, a molecule that transfers energy. To show how much we and other animals are similar to plants, the human body creates and recycles its own weight in ATP each day.

Evolutionary economy

Let’s say photosynthesis evolved in bacteria. Let’s say the first plants engulfed them as chloroplasts and the first animals engulfed them as mitochondria. These cases are called primary endosymbiosis. Secondary endosymbiosis happens when one product of primary endosymbiosis engulfs another. One solution for energy-production serves multiple orders.

Melvin Calvin (discovers how photosynthesis works)

With ukelele chords

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The Calvin cycle uses light energy to consume carbon-dioxide and water; it emits oxygen as a byproduct and produces sugar that living cells can use. Cells that use ATP as an energy source convert it back into its precursors so that it is continuously recycled. Mitochondria in a human cell produces ATP in the citric-acid cycle discovered by Hans Adolf Krebs.

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