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Question #47673
The Question
A researcher adds malonate to a suspension of human spermatozoa, which results in a rapid cessation of flagellar motility and failure of fertilization. Based on the unique location and function of the specific enzyme targeted by malonate, which of the following statements correctly identifies the primary biochemical disruption?
Options
- A.
It competitively inhibits an inner mitochondrial membrane enzyme, simultaneously arresting the TCA cycle and electron transfer at Complex II, thereby depleting ATP.
- B.
It non-competitively inhibits a mitochondrial matrix enzyme, preventing the generation of FADH2 and halting the electron transport chain at Complex I.
- C.
It competitively inhibits the conversion of alpha-ketoglutarate to succinyl-CoA in the matrix, directly blocking substrate-level phosphorylation.
- D.
It binds to the active site of an inner membrane enzyme, preventing the reduction of NAD+ to NADH + H+ and stalling the proton pump at Complex II.
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
Succinate Dehydrogenase|FAD|Complex II
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot & Location Trap: Students often forget that Succinate Dehydrogenase is the ONLY enzyme of the Krebs cycle located in the inner mitochondrial membrane (not the matrix) and that it doubles as Complex II of the ETC.
Furthermore, Complex II does not pump protons.
The question tests the integration of Biomolecules (competitive inhibition), Respiration (TCA/ETC dual function and location), and Human Reproduction (sperm energetics).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Respiration in Plants - Class 11 |
| Concept | TCA Cycle Stoichiometry |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |