Question: where are protein molecules and ion channels embedded
[{'answer': 'membrane', 'provenance': [{'wikipedia_id': '11712', 'title': 'Facilitated diffusion', 'start_paragraph_id': 1, 'start_character': 212, 'end_paragraph_id': 1, 'end_character': 220, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]