Video Transcript
Melvin Calvin investigated
photosynthesis in algae. He determined that, in the process,
a three-carbon compound was formed. What was this compound? (A) Phosphoglyceraldehyde,
PGAL. (B) Propane, C3H8. (C) Calcium carbonate, CaCO3. (D) Pyruvic acid, C3H4O3.
During photosynthesis, plants
convert carbon dioxide and water into glucose and oxygen using light energy. Melvin Calvin was an American
biochemist who was studying photosynthesis in the 1940s. Let’s have a quick look at the
basic ideas of his experiment.
In the flask, he placed a
population of chlorella algae, a living organism which carries out
photosynthesis. These algae require carbon dioxide
for photosynthesis. And they were provided with carbon
dioxide containing the isotope carbon-14. The algae were then exposed to a
brief flash of light to initiate photosynthesis. Then, the algae were quickly
dropped into a beaker of hot alcohol to kill the cells, stopping photosynthesis.
So, what did Calvin learn from
this? By studying the algae, he learnt
that even after a quick flash of light, the algae had synthesized a three-carbon
compound. This three-carbon compound is known
as phosphoglyceraldehyde, or PGAL. Phosphoglyceraldehyde can be used
to produce a range of other organic compounds that the algae need to survive, for
instance, glucose, proteins, and fats.
So, looking at our answer choices,
we now know that the three-carbon compound formed was (A),
phosphoglyceraldehyde.
