Question

3 PGA is first stable product of
a. Carbon oxidation cycle
b. Carbon reduction cycle
c. Reductive amination
d. Malic acid synthesis

Answer 1

Hint: $C_3$ plants are generally described as the plants that exhibit 3 carbon pathway, and in this plants Calvin cycle takes place in dark reaction of photosynthesis, and this plants do not have kranz anatomy, and 95% of all plants, shrubs, etc shows $C_3$ pathway.

Complete answer:
- In $C_3$ plants, most of the photosynthesis generally occurs only in the mesophyll cells, that too on the surface of the leaves.
- The plants have $C_3$ photosynthesis, they should have a cool and wet environment. Almost 95% of all plants exhibit the $C_3$ pathway.
- The $C_3$ photosynthesis is very old and common, and in this plant carbon fixation occurs only once.
- When carbon dioxide enters the chloroplast, it will be accepted by five carbon acceptors, that is called ribulose 1,5 phosphate, or this is also called ribulose 1,5 diphosphate.
- By those reactions, it yields 6 carbon intermediate products, and this product is hydrated, which cleaves to form 2 molecules of 3 carbon compounds, 3 phosphor glyceraldehydes.
- The chloroplast of $C_3$ plants have RUBISCO, and the first stable product formed in the dark reaction of Photosynthesis in these plants is 3 carbon compounds that are 3 phosphoglyceraldehyde.
- So it is carbon reduction, which commonly seen in $C_3$ plants

Hence, the correct answer is option (B).

Note: Majority of the plant species on the earth takes $C_3$ photosynthesis, where 3 carbon compounds are formed first, where some plants which are in moderate water available areas, another type of carbon fixation called $C_4$ takes place.