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Question #46791
The Question
In a laboratory experiment, a mutant strain of yeast lacking the enzyme invertase is cultured in an anaerobic medium containing sucrose as the sole respiratory substrate. Which of the following statements is NOT correct regarding the biochemical consequences in this setup?
Options
- A.
The yeast cells will fail to produce ethanol and CO2 because hexokinase cannot directly utilize sucrose for phosphorylation.
- B.
The culture medium will give a positive Benedict's test because the glycosidic bond in sucrose leaves the C2 anomeric carbon of fructose free.
- C.
The absence of invertase prevents the hydrolysis of the alpha-1, beta-2 glycosidic linkage, starving the glycolytic pathway of monosaccharides.
- D.
Addition of exogenous glucose to the medium would bypass the enzymatic block, restoring ATP production and yielding a positive Fehling's test.
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
Reducing vs Non-reducing Sugars|Enzyme Activation Energy Lowering|Sucrase
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the glycosidic linkages of disaccharides.
While maltose and lactose have free anomeric carbons (C1-C4 linkages) making them reducing sugars, sucrose has a C1-C2 linkage involving both anomeric carbons.
The trap relies on the student failing to recognize that sucrose will NEVER give a positive Benedict's test, regardless of invertase activity, because its inherent structure lacks free aldehyde or ketone groups.
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 |