Question

The ratio of ATP generated, number of ATP and NADPH + H\(^+\) needed to produce net gain of one glucose in C\(_4\) plants

• A. 1:2:1
• B. 3:2:1
• C. 4:1:2
• D. 2:3:3

Hint:

In C\(_4\) plants, the ATP/NADPH ratio is important for the carbon fixation process. Keep in mind that C\(_4\) plants require more ATP compared to NADPH during glucose synthesis.

Answer 1

The Correct Option is C

ATP and NADPH + H⁺ Utilization in C₄ Plants

In C₄ plants, the ratio of ATP, NADPH + H⁺, and ATP used for the production of glucose follows a specific metabolic pathway.

• For every molecule of glucose produced in C₄ plants:
  • ATP is required for the initial carbon fixation step and later for the regeneration of PEP (phosphoenolpyruvate). This process requires 4 ATP.
  • NADPH + H⁺ is required for the reduction steps in the Calvin cycle to convert 3-phosphoglycerate into G3P (glyceraldehyde-3-phosphate). This process requires 2 NADPH + H⁺.
  • Additional ATP is required for the regeneration of ribulose bisphosphate (RuBP), and this is usually 1 ATP.

Thus, the correct ratio of ATP generated, ATP used, and NADPH + H⁺ used is 4:1:2.

Therefore, the correct answer is (3) 4:1:2.