Question:
The organism used in the experiment in elucidation of C3 pathway :
The organism used in the experiment in elucidation of C3 pathway :
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Calvin + Chlorella + $^{14}C$ = 3-PGA (First product).
This experiment earned Melvin Calvin the Nobel Prize in Chemistry in 1961.
This experiment earned Melvin Calvin the Nobel Prize in Chemistry in 1961.
Updated On: Aug 21, 2026
- Chlorella
- Drosophila
- E. coli
- Bacillus sp.
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Question:
The question identifies the model organism used by Melvin Calvin and his team to map the biochemical path of carbon fixation in plants, known as the C3 cycle or Calvin Cycle.
Detailed Explanation:
• The Experiment:
Melvin Calvin used radioactive Carbon-14 ($^{14}C$) in the form of $^{14}CO_2$ to trace the path of carbon during photosynthesis.
The goal was to identify the first stable product formed after $CO_2$ fixation.
• The Model Organism:
He chose the single-celled green alga Chlorella (specifically Chlorella pyrenoidosa) and sometimes Scenedesmus.
Algae were preferred because they can be grown uniformly in a liquid medium, and the metabolic reactions can be stopped instantly by dropping the algae into hot boiling alcohol.
• Discovery:
Through this "kill-and-label" method followed by paper chromatography and autoradiography, he discovered that the first stable product was a 3-carbon compound, 3-phosphoglyceric acid (3-PGA).
• Analyzing other options:
Drosophila: The common fruit fly, used in genetics.
E. coli: A bacterium used in molecular biology and gene expression.
Step 2: Final Answer:
Melvin Calvin used the green alga Chlorella to elucidate the C3 pathway.
The question identifies the model organism used by Melvin Calvin and his team to map the biochemical path of carbon fixation in plants, known as the C3 cycle or Calvin Cycle.
Detailed Explanation:
• The Experiment:
Melvin Calvin used radioactive Carbon-14 ($^{14}C$) in the form of $^{14}CO_2$ to trace the path of carbon during photosynthesis.
The goal was to identify the first stable product formed after $CO_2$ fixation.
• The Model Organism:
He chose the single-celled green alga Chlorella (specifically Chlorella pyrenoidosa) and sometimes Scenedesmus.
Algae were preferred because they can be grown uniformly in a liquid medium, and the metabolic reactions can be stopped instantly by dropping the algae into hot boiling alcohol.
• Discovery:
Through this "kill-and-label" method followed by paper chromatography and autoradiography, he discovered that the first stable product was a 3-carbon compound, 3-phosphoglyceric acid (3-PGA).
• Analyzing other options:
Drosophila: The common fruit fly, used in genetics.
E. coli: A bacterium used in molecular biology and gene expression.
Step 2: Final Answer:
Melvin Calvin used the green alga Chlorella to elucidate the C3 pathway.
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