Question

According to chemiosmotic hypothesis, ATP synthetase form ADP when protons (H⁺):

• A. Move from stroma to thylakoid lumen by simple diffusion
• B. Move from stroma to thylakoid lumen by facilitated diffusion
• C. Move from thylakoid lumen to stroma by active transport
• D. Move from thylakoid lumen to stroma by facilitated diffusion

Answer 1

Answer: (D)

In non-cyclic photophosphorylation, cytochrome uses the energy of electrons from PSII to pump hydrogen ions from the lumen (an area of high concentration) to the stroma (an area of low concentration). The energy released by the hydrogen ion stream allows ATP synthase to attach a third phosphate group to ADP, which forms ATP. This 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.