Question

Which of the following pathway can produce ATP in absence of oxygen

• A. Oxidative phosphorylation
• B. Electron transport chain
• C. TCA cycle
• D. Glycolysis

Hint:

Anaerobic Energy Production: Glycolysis is the ONLY primary catabolic pathway producing net ATP (2 ATP/glucose) in the absence of oxygen.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Substrate-level phosphorylation in cytosolic anaerobic glycolysis generates ATP independently of mitochondrial oxygen availability.
Key Formula or Approach:
\[ \text{Glucose} + 2\text{ADP} + 2\text{P}_i + 2\text{NAD}^+ \longrightarrow 2\text{Pyruvate} + 2\text{ATP} + 2\text{NADH} + 2\text{H}^+ \]

Step 2: Detailed Explanation:
Under anaerobic conditions (absence of molecular oxygen):
1. Glycolysis (Embden-Meyerhof-Parnas pathway): Operates in the cytoplasm to produce a net yield of 2 ATP molecules per glucose via substrate-level phosphorylation (catalyzed by phosphoglycerate kinase and pyruvate kinase).
2. In anaerobic respiration/fermentation, lactate dehydrogenase regenerates $\text{NAD}^+$ from NADH, sustaining glycolysis without oxygen.
3. TCA cycle, ETC, and oxidative phosphorylation require oxygen as the terminal electron acceptor and shut down under hypoxia.

Step 3: Final Answer:
Therefore, Glycolysis produces ATP in the absence of oxygen, matching option (D).