In aerobic respiration diagrams, where do decarboxylation and oxidation reactions occur?

Sourav PanNovember 9, 2024

Answered

In aerobic respiration, decarboxylation and oxidation reactions occur at specific stages of the metabolic pathway, primarily in the mitochondria. Here’s a breakdown of where these reactions take place:

1. Decarboxylation Reactions

• Location: Decarboxylation occurs during two key processes:
  • Pyruvate Oxidation: After glycolysis, pyruvate (produced in the cytoplasm) is transported into the mitochondrial matrix, where it undergoes decarboxylation to form acetyl coenzyme A (acetyl CoA). This reaction releases one molecule of carbon dioxide (CO₂).
    • Enzyme: Pyruvate dehydrogenase complex catalyzes this reaction.
  • Krebs Cycle: Decarboxylation also occurs within the Krebs cycle (citric acid cycle) when α-ketoglutarate is converted to succinyl-CoA, releasing another molecule of CO₂.
    • Enzyme: α-Ketoglutarate dehydrogenase catalyzes this reaction.

2. Oxidation Reactions

• Location: Oxidation reactions occur at multiple points:
  • Glycolysis: During glycolysis, glucose is oxidized to form pyruvate. In this process, NAD+ is reduced to NADH as it accepts electrons and protons.
  • Pyruvate Oxidation: In the conversion of pyruvate to acetyl CoA, NAD+ is again reduced to NADH.
  • Krebs Cycle: Several oxidation reactions occur in the Krebs cycle:
    • Isocitrate is oxidized to α-ketoglutarate, reducing NAD+ to NADH.
    • α-Ketoglutarate is oxidized to succinyl-CoA, again reducing NAD+ to NADH.
    • Succinate is oxidized to fumarate, reducing FAD to FADH₂.
    • Malate is oxidized back to oxaloacetate, reducing NAD+ to NADH.

Summary of Locations

• Decarboxylation:
  • Occurs in the mitochondrial matrix during:
    • Pyruvate oxidation (conversion of pyruvate to acetyl CoA).
    • Krebs cycle (conversion of α-ketoglutarate to succinyl-CoA).
• Oxidation:
  • Occurs in both the cytoplasm (during glycolysis) and the mitochondrial matrix (during pyruvate oxidation and throughout the Krebs cycle).