Which stage of cellular respiration pccur in the mitochondrion?

Answer 1

after glycolysis, the two pyruvates become acetyl-CoA and enter the

citric acid cycle in the mitochondrion

after that, oxidative phosphorylation starts. First, there is the electron transport chain in the inner membrane of the mitochondrion, which involves using the electrons from NADH (it then becomes NAD+) to power H+ ions from the mitochondrial matrix to the inner membrane space, and eventually back through a protein called ATP synthase into the mitochondrial matrix again. The last part is referred to as chemiosmosis.

As you can see, most of cellular respiration ("step 2" and "step 3") occur in the mitochondrion of cells.