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Question #45210
The Question
In an experiment, a synthetic milk analog containing pure casein, water, and sucrose (as the sole carbohydrate source) is inoculated with a standard Lactobacillus strain that lacks the enzyme invertase. The mixture is incubated at 40°C. After 24 hours, no coagulation of the protein is observed. Which of the following statements correctly identifies the biochemical reason for this failure?
Options
- A.
The absence of a metabolizable reducing sugar prevents the initial glycolytic flux, halting lactic acid production and the subsequent pH drop required to denature casein.
- B.
Lactobacillus requires lactose specifically to induce the lac operon, without which the enzymes for lactic acid synthesis cannot be transcribed.
- C.
Sucrose acts as a competitive inhibitor for the proteolytic enzymes secreted by Lactobacillus, preventing the partial digestion of milk proteins.
- D.
The breakdown of sucrose yields fructose, which allosterically inhibits lactate dehydrogenase, preventing the final step of fermentation.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Reducing vs Non-reducing Sugars|Household Product Fermentation Specificity|Metabolic Pathway
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the NCERT fact 'LAB converts milk to curd' without understanding the biochemical dependency on the specific substrate (lactose) and the mechanism of coagulation (pH-induced denaturation).
The trap in Option B leverages the 'lac operon' concept from Molecular Basis of Inheritance, creating a highly plausible 'Half-Truth' distractor that confuses lactose metabolism with the fundamental pathway of lactic acid fermentation.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biomolecules - Class 11 |
| Concept | Reducing vs Non-reducing Sugars |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |