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Question #47604
The Question
During the artificial transformation of E. coli, cells are treated with divalent cations (Ca²⁺) and subjected to a heat shock (42°C) to facilitate the entry of recombinant DNA. This process creates transient pores in the cell envelope. If these cells are immediately plated on an antibiotic-containing medium without a prior recovery incubation in a nutrient broth, transformation efficiency drops drastically. Beyond allowing time for the expression of the selectable marker, what is the fundamental bioenergetic necessity of this recovery phase?
Options
- A.
The transient membrane disruption partially collapses the proton gradient, halting chemiosmotic ATP synthesis; recovery is needed to restore the proton motive force.
- B.
The heat shock at 42°C transiently denatures the plasmid DNA, and the recovery phase provides the ATP required for DNA ligase to re-anneal the strands.
- C.
The influx of Ca²⁺ ions competitively inhibits the F₀-F₁ ATP synthase complex, and the nutrient broth is required to chelate these ions.
- D.
The recovery phase allows the bacterial cell to switch from anaerobic glycolysis to aerobic respiration, which is strictly necessary for plasmid replication.
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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
ATP-Synthase|Competent Cell Preparation|Transformation Efficiency
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Integrating Biotechnology (Competency) with Respiration (Chemiosmosis).
Students often memorize the heat-shock protocol but fail to realize that permeabilizing a biological membrane inherently destroys the proton gradient required for ATP synthesis.
This question tests the ability to link the structural requirements of the chemiosmotic hypothesis with the physical realities of genetic engineering techniques.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | Chemiosmotic ATP Synthesis Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |