The Question is from neet-botany , and it was created by the author Mr. NARESH KUMAR K

Question

The Pasteur effect describes the inhibitory effect of oxygen on fermentation.  This inhibition is primarily due to:

Mr. NARESH KUMAR K · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Cellular Respiration and Fermentation
 **Related Topics**: Glycolysis, Electron Transport Chain, ATP production, Metabolic regulation
 **Prerequisites**: Understanding of aerobic and anaerobic respiration, glycolysis, and the role of NADH and ATP.
## SOLUTION PATHWAY
**Given Information**:
  The Pasteur effect describes the inhibition of fermentation by oxygen.
  We need to identify the primary cause of this inhibition.
**Method & Steps**:
 1. Analyze the options to determine the mechanism behind oxygen's inhibitory effect on fermentation.
  Reasoning: Oxygen's presence shifts metabolism from fermentation to aerobic respiration, a much more efficient ATP-producing pathway.
 2. Consider the role of ATP and NADH in both fermentation and aerobic respiration.
  Working: Fermentation relies on glycolysis, producing a small amount of ATP and regenerating NAD+ from NADH.  Aerobic respiration, through oxidative phosphorylation, generates significantly more ATP.  The high ATP levels from aerobic respiration inhibit glycolysis through feedback mechanisms.
  Key Point: The key is understanding that the presence of oxygen leads to a significant increase in ATP production, which then inhibits the earlier steps of glucose metabolism, including glycolysis, which is essential for fermentation.
 3. Determine which option best explains the shift from fermentation to aerobic respiration in the presence of oxygen.
  Result: Option C, 'Feedback inhibition of glycolytic enzymes by ATP and citrate', correctly identifies the primary mechanism.  Citrate is an intermediate in the citric acid cycle (part of aerobic respiration), its accumulation further signals high energy levels and inhibits glycolysis.
  Verification: The other options are less accurate.  Oxygen doesn't directly inhibit fermentative enzymes, and while the electron transport chain is more active, the primary effect isn't direct inhibition of fermentation but rather a shift in metabolic pathways due to high ATP levels.
 ## OPTION ANALYSIS
A :x: Direct inhibition of fermentative enzymes by oxygen: Oxygen doesn't directly inhibit fermentative enzymes. The inhibition is indirect, through metabolic regulation.
B :x: Increased activity of the electron transport chain: While true, this is a consequence of oxygen's presence, not the primary cause of fermentation inhibition.
C ✓: Feedback inhibition of glycolytic enzymes by ATP and citrate: This is the correct answer. High ATP levels (due to aerobic respiration) inhibit glycolysis, thus reducing fermentation.
D :x: Depletion of NADH required for fermentation: NADH is used in fermentation, but its depletion is not the primary reason for inhibition. The shift to aerobic respiration utilizes NADH more efficiently.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing direct and indirect inhibition: The Pasteur effect is an indirect effect, mediated by ATP and other metabolic regulators.
  2.Focusing solely on the electron transport chain: While the ETC is activated by oxygen, the primary cause of fermentation inhibition is the feedback regulation of glycolysis.
 **Quick Tips**:
  1.Remember that aerobic respiration is far more efficient than fermentation in ATP production.
  2.Understand the role of feedback inhibition in metabolic regulation.

Mr. NARESH KUMAR K · Answer

Direct inhibition of fermentative enzymes by oxygen

Mr. NARESH KUMAR K · Answer

Increased activity of the electron transport chain

Mr. NARESH KUMAR K · Answer

The correct Option is "Feedback inhibition of glycolytic enzymes by ATP and citrate"

Mr. NARESH KUMAR K · Answer

Depletion of NADH required for fermentation

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