Final answer:
Proton flow occurs in cellular processes such as oxidative phosphorylation, photosynthesis, and chemiosmosis.
Step-by-step explanation:
Proton flow occurs in various cellular processes such as oxidative phosphorylation, photosynthesis, and chemiosmosis. In oxidative phosphorylation, proton flow happens in the mitochondria through the inner membrane, creating a proton gradient that powers the synthesis of ATP. In photosynthesis, proton flow occurs in the inner chloroplast membrane, generating a proton gradient to produce ATP. In chemiosmosis, proton flow takes place across the inner mitochondrial membrane, creating an electrochemical gradient that drives ATP synthesis.
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