Question Video: Explaining the Steps of Melvin Calvin’s Photosynthetic Experiments | Nagwa Question Video: Explaining the Steps of Melvin Calvin’s Photosynthetic Experiments | Nagwa

Question Video: Explaining the Steps of Melvin Calvin’s Photosynthetic Experiments Biology • Second Year of Secondary School

Melvin Calvin investigated photosynthesis in algae. The diagram demonstrates a simplified outline of his experiment. Why is the algae subjected to a quick flash of light?

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Video Transcript

Melvin Calvin investigated photosynthesis in algae. The diagram demonstrates a simplified outline of his experiment. Why is the algae subjected to a quick flash of light? (A) To initiate cell division. (B) To stop respiration. (C) To initiate photosynthesis. (D) To begin digestion. (E) To kill the cells.

During photosynthesis, plants convert carbon dioxide and water into glucose and oxygen using light energy. Without light energy, the reactions of photosynthesis cannot proceed.

Melvin Calvin was an American biochemist who was studying photosynthesis in the 1940s. Calvin used different isotopes of carbon in his work. So let’s ensure that we understand what isotopes are before we look at his experiment.

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. The most common isotope of carbon is carbon-12, which has six protons and six neutrons. Carbon-14 is a different isotope of carbon that has six protons and eight neutrons. Carbon-14 is radioactive and can therefore be tracked at experiments, like the one carried out by Calvin.

Let’s take a closer look at Calvin’s experiment into photosynthesis. In the flask, there is a population of Chlorella algae. These algae were provided with carbon dioxide which contained the carbon-14 isotope. The algae was then exposed to a quick flash of light to initiate photosynthesis. Then they were quickly dropped in a beaker of hot alcohol to stop photosynthesis.

By studying the algae, Calvin discovered that even after a very quick flash of light, a three-carbon compound was formed. This three-carbon compound is known as phosphoglyceraldehyde, or PGAL. PGAL can be used to produce a range of other organic compounds essential for an organism’s survival, such as glucose, proteins, and fats.

Melvin Calvin’s work was so important that you will often see the light-independent reactions of photosynthesis referred to as the Calvin cycle.

Using what we now know about Calvin’s experiments, let’s take a look back at the question. The correct answer is option (C). In Calvin’s experiment, the algae is subjected to a quick flash of light to initiate photosynthesis.

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