Final answer:
Substrate-level phosphorylation is a process in which ATP is synthesized by the transfer of a phosphate group from an organic molecule to ADP. Phosphoglycerate kinase catalyzes this transfer during the energy payoff phase of glycolysis.
Step-by-step explanation:
Substrate-level phosphorylation is a process in which ATP is synthesized by the transfer of a phosphate group from an organic molecule to ADP. In glycolysis, the enzyme phosphoglycerate kinase catalyzes the transfer of a high-energy phosphate from 1,3-bisphosphoglycerate to ADP, resulting in the formation of one molecule of ATP. This process occurs during the energy payoff phase of glycolysis. The phosphate group is removed from 1,3-bisphosphoglycerate, which is oxidized to form 3-phosphoglycerate.