Before You Begin
Question #45939
The Question
A yeast strain is forced into strict anaerobiosis (alcoholic fermentation) in a culture medium that eventually becomes depleted of carbohydrates but remains rich in fatty acids. The cells fail to utilize the fatty acids for survival and perish. Which of the following correctly identifies the metabolic bottleneck preventing lipid utilization, and the Respiratory Quotient (RQ) of the cells while they were actively fermenting carbohydrates?
Options
- A.
-oxidation of fatty acids requires an active electron transport chain to regenerate and FAD; RQ approaches infinity.
- B.
Fatty acids yield acetyl-CoA which cannot be directly reduced to ethanol; RQ is 0.7.
- C.
The absence of oxygen prevents the conversion of glycerol to dihydroxyacetone phosphate (DHAP); RQ is zero.
- D.
Lipids require a higher number of oxygen molecules for oxidation, causing immediate cellular toxicity; RQ is 1.0.
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
Glucose|Lipids|Alcohol_Dehydrogenase
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often reflexively associate 'fatty acids' with an RQ of 0.7 (Option B trap).
However, the question asks for the RQ during active carbohydrate fermentation (which is infinity).
Furthermore, it tests the deep NCERT-Plus concept of why fats cannot be fermented: -oxidation is obligately aerobic because it relies on the ETC to recycle electron carriers (/FAD), a detail often overlooked when studying substrate switching.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Respiration in Plants - Class 11 |
| Concept | Fermentation Limitations |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |