This page discusses the chemiosmotic theory of ATP synthesis in chloroplasts, supported by observations that light illumination increases the alkalinity of the surrounding medium due to proton pumping...This page discusses the chemiosmotic theory of ATP synthesis in chloroplasts, supported by observations that light illumination increases the alkalinity of the surrounding medium due to proton pumping. It describes how altering the thylakoid pH by using acidic mediums allows chloroplasts to synthesize ATP in alkaline conditions with ADP and inorganic phosphate, showcasing the role of the proton gradient in ATP production even in the absence of light.