Best Answer: a) by the transfer of a phosphate group from a fragment of sugar to ADP. ATP is produced during glycolysis through substrate-level phosphorylation; producing ATP using ATP synthase in mitochondria is through oxydative phosphorylation, and in plants, it's called photophosphorylation, using light to produce ATP. They use ATP synthase, very similar to that in mitochondria; but plant ATP synthase is located in the membrane of chlorplast!