Question

Carbon in carbon dioxide is radioactively labelled. The product in which radioactive carbon can be traced in $C_3$ plants is

• A. PEP
• B. RuBP
• C. OAA
• D. PGA

Answer 1

The correct option is D PGA

Calvin used the radioactive isotope of carbon (${}^1$${}^4$C) of Chlorella. He observed that after second exposure of Chlorella in presence of ${}^1$${}^4$CO${}_2$, the radioactive isotope of carbon was found mainly in 3-phosphoglyceric acid (PGA). This clearly indicated that the three carbon compound 3- phosphoglyceric acid was the first stable product photosynthesis and the carbon from the CO${}_2$ is fixed in the preparation of the photosynthates.

Hence, the correct answer is 'PGA'.