What happens to glycolysis if oxygen is not present?

Sourav PanAugust 19, 2024

Answered

If oxygen is not present, glycolysis itself continues to occur normally, as it does not require oxygen. However, the fate of the pyruvate produced by glycolysis differs depending on whether oxygen is available:

1. Glycolysis Overview:

• Process: Glycolysis is the breakdown of glucose into pyruvate, producing a small amount of ATP and NADH in the process.
• Reaction: C6​H1​2O6​→2C3​H4​O3​+2ATP+2NADH

2. In the Presence of Oxygen (Aerobic Conditions):

• Pyruvate enters the mitochondria and undergoes aerobic respiration through the citric acid cycle (Krebs cycle) and oxidative phosphorylation, producing a large amount of ATP.

3. In the Absence of Oxygen (Anaerobic Conditions):

• Pyruvate undergoes fermentation to regenerate NAD⁺, which is necessary for glycolysis to continue.

Anaerobic Processes:

• In Yeast (Alcoholic Fermentation):
  • Pyruvate is converted into ethanol and carbon dioxide.
  • Reaction: C3​H4​O3​→C2​H5​OH+CO2​​
  • NADH is oxidized to NAD⁺ in this process.
• In Muscle Cells (Lactic Acid Fermentation):
  • Pyruvate is converted into lactic acid.
  • Reaction: C3​H4​O3​→C3​H6​O3​​
  • NADH is oxidized to NAD⁺ in this process.

Summary:

In the absence of oxygen, glycolysis continues, but the pyruvate produced is not fully oxidized. Instead, it is redirected into fermentation pathways to regenerate NAD⁺, allowing glycolysis to proceed and produce a limited amount of ATP.