What is chemiosmosis?

A. Coupling of ATP synthesis to the electron transport and proton movement
B. Phosphorylation of glucose in the mitochondrial matrix
C. H⁺ ions moving down a concentration gradient into the mitochondrial matrix
D. Activation of ATPase in order to synthesize ATP

A

This caused more difficulty to candidates than expected though the better-prepared candidates mostly answered it correctly. In AS 8.1.5 and AS 8.2.4 it is clear that chemiosmosis involves the synthesis of ATP. This is achieved using potential energy stored in the form of a proton gradient and this gradient is built up by electron transport. The correct answer was therefore A. Answer C should have been rejected because it does not include ATP synthesis and it refers to the mitochondrion only, excluding chemiosmosis in photosynthesis.