Question

Sesquiterpenes are biosynthesised from ______ in plants.

• A. Farnesyl-pyrophosphate
• B. Geranyl farnesyl pyrophosphate
• C. Terpenes
• D. Degraded products of terpenes

Answer 1

The Correct Option is A

Sessquiterpenes are a class of terpenes that consist of three isoprene units and have the molecular formula C₁₅H₂₄. They play various roles in plants, including serving as a defense mechanism against herbivores and pathogens.

The question asks about the biosynthetic precursor of sesquiterpenes in plants. To answer this, we need to understand the process of terpene biosynthesis, which involves the following key steps:

1. In plants, the biosynthesis of terpenes begins with the combination of isoprene units. Isopentenyl pyrophosphate (IPP) is the basic building block.
2. The biosynthesis of sesquiterpenes is specifically initiated by the formation of farnesyl pyrophosphate (FPP). This compound is created by the condensation of one molecule of IPP and two molecules of dimethylallyl pyrophosphate (DMAPP).
3. Farnesyl-pyrophosphate (FPP) then acts as the direct precursor for sesquiterpenes in plants.

In this context, let's examine the options provided:

• Farnesyl-pyrophosphate: This is indeed the correct precursor for sesquiterpenes, as explained above. It is the C₁₅ precursor from which various sesquiterpenes are biosynthesized.
• Geranyl farnesyl pyrophosphate: This is not directly involved in the synthesis of sesquiterpenes. It is actually a precursor for longer-chain polyterpenes.
• Terpenes: These are a broader class of compounds that includes monoterpenes, sesquiterpenes, diterpenes, etc. They cannot be the direct precursor for sesquiterpenes.
• Degraded products of terpenes: This is not accurate, as sesquiterpenes are synthesized, not degraded, from specific precursors.

Thus, the correct answer is Farnesyl-pyrophosphate, as it is the specific precursor required for the biosynthesis of sesquiterpenes in plants.