Before You Begin

Question #47611

Difficulty: 8/10 | 🟢 Free

The Question

In an experiment, a transgenic tomato plant is created using antisense RNA technology. Due to an off-target effect, the antisense RNA partially silences the specific stromal enzyme responsible for the phosphorylation of Ribulose-5-phosphate. Which of the following best describes the immediate stoichiometric bottleneck in the $C_3$ cycle and its downstream physiological consequence?

Options

A.
The regeneration phase fails to consume its standard 1 ATP per $CO_2$ fixed, leading to Ribulose-5-phosphate accumulation, halted carbon fixation, and delayed ethylene-mediated ripening due to substrate starvation.
B.
The reduction phase fails to consume its standard 2 ATP and 2 NADPH per $CO_2$ fixed, causing an accumulation of 3-PGA and premature activation of polygalacturonase.
C.
The stoichiometry of the $C_3$ cycle shifts to require 3 ATP and 2 NADPH exclusively for the reduction phase, accelerating the degradation of the middle lamella.
D.
The plant compensates by upregulating cyclic photophosphorylation to provide the missing ATP, thereby accelerating ethylene production and fruit softening.

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Regulatory_Failure

Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.

Concepts Behind This Question

C3 Cycle Stoichiometry|Flavr Savr Tomato Logic|Rubisco

Why This Question Is Tricky

Common Mistakes

Conceptual Pivot: Distinguishing the exact stoichiometric breakdown of the Calvin cycle (2 ATP/2 NADPH for reduction vs. 1 ATP for regeneration) and linking primary photosynthetic carbon fixation to downstream biotechnological/physiological outcomes (ethylene synthesis and ripening).

Students often memorize the net '3 ATP and 2 NADPH' without understanding the phase-specific allocation, making them vulnerable to traps that mix up the reduction and regeneration steps.

Quick Facts About This Question

Question Information

Subject	Biology
Chapter	Photosynthesis in Higher Plants - Class 11
Concept	C3 Cycle Stoichiometry
Difficulty	8
Cognitive Load	5
Target Solve Time	120 sec
Access	Free