According to this theory, how did mitochondria evolve?

Mitochondria evolved from endosymbiotic prokaryotes that were able to use oxygen to generate energy rich ATP. To prokaryotes then evolved into mitochondria that now power the cells of all multicellular organisms.

Explanation:

According to this theory mitochondria evolved from bacteria and somehow became incorporated into the cytoplasm.

Explanation:

i don't know which theory ur talking about but this theory is the endosymbiotic theory

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products