bio Q

[bumpski20]

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in the kaplan notes it says pyruvate decarboxylation and the citric acid cycle take place in the mitochondria, and the electron transport chain is in the mitochondrial matrix...but then it said on the solutions to one of the kaplan tests, that decarboxylation is in the cytoplasm, acid cycle is in the matrix and the transport chain is the the inner membrane. which one was right?

 

[denticus]

in the kaplan notes it says pyruvate decarboxylation and the citric acid cycle take place in the mitochondria, and the electron transport chain is in the mitochondrial matrix...but then it said on the solutions to one of the kaplan tests, that decarboxylation is in the cytoplasm, acid cycle is in the matrix and the transport chain is the the inner membrane. which one was right?

The later is closer exept for the decarboxylation reaction. In eukaryotic cells the pyruvate decarboxylation occurs inside the mitochondria, after transport of the substrate, pyruvate, from the cytosol. The transport of pyruvate into the mitochondria is via a transport protein and is active, consuming energy. Passive diffusion of pyruvate into the mitochondria is impossible because it is a polar molecule.

On entry to the mitochondria the pyruvate decarboxylation occurs, producing acetyl CoA. This irreversible reaction traps the acetyl CoA within the mitochondria (there is no transporter for acetyl CoA). The carbon dioxide produced by this reaction is nonpolar and small, and can diffuse out of the mitochondria and out of the cell.

In prokaryotes, which have no mitochondria, this reaction is either carried out in the cytosol, or not at all.

 

[TheWiredNerv]

Electron transport chain takes place in the inner mitochondrial membrane, not the matrix. As denticus said, decarboxylation of pyruvate occurs in the mito.

 

[bumpski20]

k thanks!