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What is the Breakdown of Pyruvate?

Published in Cellular Metabolism 2 mins read

Pyruvate, a crucial molecule in cellular metabolism, is broken down into carbon dioxide and water within the mitochondria. This process extracts energy to fuel cellular functions.

The Fate of Pyruvate: From Cytosol to Mitochondria

After glycolysis, pyruvate resides in the cytoplasm. To continue its breakdown and release more energy, it must enter the mitochondria.

  • Transport: Pyruvate is actively transported across the mitochondrial membrane.

Pyruvate Decarboxylation and the Citric Acid Cycle

Within the mitochondrial matrix, the breakdown of pyruvate continues through a series of reactions:

  1. Pyruvate Decarboxylation: Pyruvate dehydrogenase complex (PDC) converts pyruvate into acetyl-CoA, releasing carbon dioxide as a byproduct. This is a crucial step linking glycolysis to the citric acid cycle.

    • Reaction: Pyruvate + CoA + NAD+ → Acetyl-CoA + CO2 + NADH + H+

  2. Citric Acid Cycle (Krebs Cycle): Acetyl-CoA enters the citric acid cycle. This cycle further oxidizes the acetyl group, releasing more carbon dioxide and generating energy-rich molecules (NADH, FADH2) and a small amount of ATP (or GTP).

Electron Transport Chain and Oxidative Phosphorylation

The NADH and FADH2 produced during glycolysis and the citric acid cycle then donate electrons to the electron transport chain (ETC), located in the inner mitochondrial membrane.

  • Electron Transport: As electrons move through the ETC, protons (H+) are pumped from the mitochondrial matrix into the intermembrane space, creating an electrochemical gradient.
  • ATP Synthesis: The flow of protons back across the membrane, through ATP synthase, drives the synthesis of ATP from ADP and inorganic phosphate. This process is called oxidative phosphorylation.
  • Water Formation: At the end of the ETC, electrons combine with oxygen and protons to form water.

Breakdown Products Summary

In summary, the breakdown of pyruvate ultimately yields:

  • Carbon Dioxide (CO2): Released during pyruvate decarboxylation and the citric acid cycle.
  • Water (H2O): Formed at the end of the electron transport chain.
  • Energy (ATP): Generated primarily through oxidative phosphorylation, driven by the electron transport chain and the proton gradient created by it.

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