Chemiosmosis is defined as

• A. Synthesis of glucose
• B. Movement of hydrogen ions across the cristae during ATP production
• C. Transport of electrons through complex
• D. Import of ADP into mitochondria

Answer: (B)

Chemiosmosis is the use of a proton (H+) gradient across a membrane to drive ATP synthesis. In mitochondria, electrons pass through the electron transport chain in the inner membrane (cristae) and pump protons from the matrix into the intermembrane space, building a strong electrochemical gradient. Protons flow back into the matrix through ATP synthase, and the energy of this flow powers the enzyme to convert ADP and inorganic phosphate into ATP. This coupling of proton movement to ATP production is the essence of chemiosmosis.

The other options describe different processes: making glucose is a separate metabolic pathway; moving electrons through the complexes is the electron transport chain itself, not the proton-driven ATP synthesis; and importing ADP into mitochondria is a transport step, not the energy-conserving mechanism that produces ATP.