The flow of hydrogen ions through ATP synthase is called:

1. Hydrogen ions build up on one side of the thylakoid membrane. 2. They then move down their gradient through a single protein channel. 3. The flow of hydrogen ions through ATP synthase is called chemiosmosis because the ions move from an area of high to an area of low concentration through a semi-permeable structure. 4. The energy released by that stream allows ATP synthase to attach a third phosphate group to ADP. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 8 'Photosynthesis', sections 8.1-8.3_