Question

PEP is primary ${C}{O}_{2}$ acceptor in
(a) ${C}_{4}$
(b) ${C}_{3}$
(c) ${C}_{2}$
(d) Both ${C}_{3}$ and ${C}_{4}$ plants

Answer 1

Hint: It's one of three known processes for carbon fixation in some plants. In this, a 4-carbon compound which is called oxaloacetic acid (OAA) is the first product by carbon fixation. Plants in tropical desert regions commonly follow this pathway.

Complete answer:
In ${C}_{4}$ plants, the initial fixation of ${C}{O}_{2}$ or carboxylation takes place in mesophyll cells. The chloroplasts of mesophylls cells possess enzyme PEP carboxylase for initial fixation of ${C}{O}_{2}$. The first acceptor of ${C}{O}_{2}$ is phosphoenolpyruvate or PE, which is a 3-carbon molecule. It combines with ${C}{O}_{2}$ within the presence of PEP carboxylase to make oxaloacetic acid or oxaloacetate (OAA) , which is a 4-carbon molecule. Eventually, it's converted into another 4-carbon compound referred to as malic acid.
Later, they're transferred from mesophyll cells to bundle sheath cells. Here, OAA is weakened to yield ${C}{O}_{2}$ and a 3-C molecule. The ${C}{O}_{2}$ thus formed is employed within the Calvin cycle, whereas 3-carbon molecule is transferred back to mesophyll cells for regeneration of PEP
-The majority of plants produce 3-carbon acid called 3-phosphoglyceric acid (PGA) as a primary product during ${C}{O}_{2}$ fixation. Such a pathway is understood because the ${C}_{3}$ pathway which is additionally called the Calvin cycle. -Photorespiration is known as ${C}_{2}$ cycle. Occurs in photosynthetic organisms. It is light-dependent, where ${ O }_{ 2 }$ is taken, and ${C}{O}_{2}$ is released. In this metabolic pathway, sugars are oxidized to ${C}{O}_{2}$ in the light.
So, the correct answer is ‘${C}_{4}$‘.

Note: Corn, sugarcane, and a few shrubs are samples of plants that follow the ${C}_{4}$ pathway. The Calvin pathway may be a common pathway in both ${C}_{3}$ plants and ${C}_{4}$ plants. But this takes place only within the mesophyll cells of the ${C}_{3}$ plants and not within the ${C}_{4}$ plants.