[Campbell Biology P.253] The text states that the regeneration of PEP from pyruvate in C4 ph... | Practice Question

The text states that the regeneration of PEP from pyruvate in C4 photosynthesis requires ATP. What is the significance of this energy cost in the context of C4 plant adaptation?

  • A: It indicates that C4 plants are less efficient overall than C3 plants.
  • B: It represents the "price" C4 plants pay to concentrate CO2, thereby minimizing photorespiration and enhancing sugar production.
  • C: It allows C4 plants to perform photosynthesis at night.
  • D: It is primarily used for water transport within the plant.

Explanation

The regeneration of PEP from pyruvate requires ATP, which represents an additional energy expenditure for C4 plants compared to C3 plants. This 'price' is paid to concentrate CO2 in the bundle-sheath cells, which ensures that rubisco functions primarily as a carboxylase and minimizes photorespiration, leading to increased photosynthetic efficiency in hot, dry environments.