Pyruvate enters the mitochondrion via active transport utilizing a specific transport protein called pyruvate translocase.
Here's a breakdown of the process:
- Pyruvate Production: Glycolysis, which occurs in the cytosol, produces pyruvate.
- Mitochondrial Membrane: The mitochondrion has two membranes: an outer membrane and an inner membrane. The inner mitochondrial membrane is highly selective and impermeable to many molecules, including pyruvate.
- Pyruvate Translocase: Pyruvate translocase is a transmembrane protein located on the inner mitochondrial membrane. It facilitates the movement of pyruvate across the membrane.
- Active Transport: The transport of pyruvate is coupled to the movement of a proton (H+) in the same direction (symport). This process is considered active transport because it requires energy indirectly (the proton gradient is maintained by the electron transport chain).
- Inside the Mitochondria: Once inside the mitochondrial matrix, pyruvate is converted to acetyl-CoA by the pyruvate dehydrogenase complex (PDC). Acetyl-CoA then enters the citric acid cycle for further energy production.
In summary, pyruvate does not simply diffuse into the mitochondrion. It requires the action of the pyruvate translocase protein to actively transport it across the inner mitochondrial membrane, ensuring its entry into the mitochondrial matrix for further metabolic processing.
