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

Sourav PanNovember 9, 2024

Answered step-by-step

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).