35. Which of the following is a plant secondary metabolite?
(1)  Kaurenoic acid
(2) Abietic acid
(3) Proline
(4) Pyruvate

Correct answer: (1) Kaurenoic acid

Explanation:

• Kaurenoic acid is a diterpenoid, a class of plant secondary metabolites derived from isoprenoid biosynthesis pathways. It is known for its various biological activities including antimicrobial and anti-inflammatory effects. Thus, it is a plant secondary metabolite.

• Abietic acid is also a diterpenoid resin acid primarily found in conifers and serves as a defensive resin component; it is a secondary metabolite.

• Proline is an amino acid, which is a primary metabolite essential for protein synthesis and plant growth. It is not a secondary metabolite.

• Pyruvate is a key intermediate in primary metabolism, central to cellular respiration and energy production. It is a primary metabolite, not a secondary metabolite.

Option-wise:

• (1) Kaurenoic acid — Correct plant secondary metabolite.

• (2) Abietic acid — Secondary metabolite but not correct choice here since multiple metabolites cannot be correct; Kaurenoic acid is more specific answer for plant secondary metabolite context.

• (3) Proline — Primary metabolite.

• (4) Pyruvate — Primary metabolite.

Kaurenoic acid is part of the diterpenoid class of plant secondary metabolites involved in defense and signaling, unlike proline and pyruvate which are primary metabolites essential to cellular function and growth.