MCAT Official Prep (AAMC)
Practice Exam 1 B/B Section Passage 2 Question 10
• During chemiosmosis, the free energy from the series of reactions that make up the electron transport chain is used to pump hydrogen ions across the membrane, establishing an electrochemical gradient.
• Hydrogen ions in the matrix space can only pass through the inner mitochondrial membrane through a membrane protein called ATP synthase.
• As protons move through ATP synthase, ADP is converted into ATP through the addition of an inorganic phosphate (Pi).
• The production of ATP through the process of chemiosmosis in mitochondria is called oxidative phosphorylation.
Chemiosmotic coupling: The process that links the electron transport chain to the production of ATP through ATP synthase.
ATP synthase: A molecular machine that uses a proton (H+) gradient to form ATP from ADP and inorganic phosphate (Pi).
Electrochemical gradient: The combination of a concentration gradient and electrical gradient due to an unequal distribution of ions across a membrane.
Chemiosmosis: The movement of ions across a selectively permeable membrane, down their electrochemical gradient.
Electron transport chain: A series of proteins embedded in the inner mitochondrial membrane that takes up highly energetic electrons from NADH and FADH2 and uses the energy to form proton gradient across the membrane.