Question: what uses the energy found within a proton gradient to drive the synthesis of atp
[{'answer': 'oxidative phosphorylation or photophosphorylation', 'provenance': [{'wikipedia_id': '2821615', 'title': 'Electrochemical gradient', 'start_paragraph_id': 4, 'start_character': 350, 'end_paragraph_id': 4, 'end_character': 399, 'bleu_score': 1.0, 'section': 'Section::::Overview.\n'}]}, {'provenance': [{'wikipedia_id': '2821615', 'title': 'Electrochemical gradient', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 413, 'bleu_score': 0.9669306597086381, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5856299579886814557}, 'section': 'Section::::Overview.\n'}]}]