Video Transcript
Melvin Calvin investigated
photosynthesis in algae. The diagram demonstrates a
simplified outline of his experiment. After the algae is subjected to a
quick flash of light, why is it dropped into a flask of hot alcohol? (A) To begin digestion. (B) To initiate cell division. (C) To revive the cells. (D) To begin respiration. Or (E) to stop photosynthesis.
With his experiments, Melvin Calvin
was able to make key advancements in our understanding of the process of
photosynthesis. Calvin developed the experiment
shown in the diagram.
In the first step of the
experiment, algae was given access to carbon dioxide containing carbon-14. Carbon-14 is an isotope of carbon
which has eight neutrons in its atomic nucleus instead of the six most carbon atoms
have. In the second step, the algae were
exposed to a brief flash of light and dropped in hot alcohol. This experiment allowed scientists
to analyze the products of photosynthesis. We are trying to figure out why the
algae is dropped into a flask of hot alcohol.
Hot alcohol kills the cells by a
process called denaturation, which destroys the membranes and allows the contents of
the cells to leak out.
Now that we know some background
information, we can eliminate the incorrect answers. The alcohol will not initiate
anything in the cells. It neither prompts digestion nor
cell division nor respiration. So answers (A), (B), and (D) are
all incorrect. Additionally, answer (C), to revive
the cells, is also incorrect, because the algae is alive during the experiment and
is killed upon contact with the hot alcohol.
As the cells die after dropping
into the hot alcohol, photosynthesis stops. This allows the scientist to see
what molecules are produced in the initial reaction to light, because the process of
photosynthesis stopped soon after the brief light exposure. The correct answer is therefore
(E). After the algae is subjected to a
quick flash of light, it is dropped into a flask of hot alcohol to stop
photosynthesis.
