The correct answer is inner membrane. Key Points - Mitochondria are made up of two membranes: the outer and inner mitochondrial membranes. - The inner mitochondrial membrane is folded several times to form cristae and contains F0-F1 particles, which are the electron transport system's particles. - The inner membrane is likewise densely packed with proteins involved in ATP generation, and here is frequently where ATP is produced. - Adenosine triphosphate (ATP) is the energy currency for cellular processes. ATP provides energy for both energy-consuming endergonic reactions and energy-releasing exergonic reactions, which require a small input of energy.