Correct option is D
Important Key Points:
MEP Pathway Location:
The MEP pathway (methyl erythritol phosphate pathway) operates in the plastids of plant cells. Plastids include chloroplasts and other related organelles.Mevalonate Pathway Location:
The mevalonate pathway occurs in the cytosol of plant cells.Terpenoid Biosynthesis Roles:
The MEP pathway primarily supplies the C₅ units (isopentenyl diphosphate and dimethylallyl diphosphate) for the biosynthesis of monoterpenes (C₁₀) and diterpenes (C₂₀).
The mevalonate pathway mainly contributes C₅ units for sesquiterpenes (C₁₅) and other compounds synthesized in the cytosol.
Gene Origin:
Certain genes in the plant MEP pathway are believed to have been acquired through endosymbiotic gene transfer from cyanobacterial ancestors, supporting the evolutionary origin of plastids from cyanobacteria.
Knowledge Booster:
Why option B is incorrect:
Statement B claims that the mevalonate pathway supplies most of the C₅ units for monoterpenes and diterpenes, but in reality, the MEP pathway in plastids is responsible for these terpenoids, not the mevalonate pathway.Why option C is incorrect:
Statement C says the MEP pathway supplies most of the C₅ units for sesquiterpenes. However, sesquiterpenes are generally synthesized via the mevalonate pathway in the cytosol, not via the MEP pathway.This compartmentalization in plants allows for regulation and diversification of terpenoid biosynthesis depending on cellular location and precursor pathways.
