- A The semi-conservative unwinding and copying of the double helix by DNA polymerase
- B The proton gradient mechanism in chloroplast thylakoids during photosynthesis
- C The stepwise cytoplasmic breakdown of glucose into pyruvate
- D The carrier-mediated movement of glucose against its concentration gradient
Correct answer: B. The proton gradient mechanism in chloroplast thylakoids during photosynthesis
Explanation: Both mitochondrial oxidative phosphorylation and chloroplast photophosphorylation use a proton gradient across a membrane to drive ATP synthase — the same fundamental chemiosmotic principle, just in different organelles and directions.
Concept context
Glycolysis, the Krebs cycle, the electron transport chain, fermentation, and the respiratory quotient. The cellular energy-release counterpart to photosynthesis.