Mitochondrial function, dynamics, and quality control

This chapter provides a summary of the conserved features of mitochondria, with a focus on hepatocyte mitochondrial oxidative phosphorylation (OXPHOS) function and the role of mitochondrial dynamics in hepatocytes determining OXPHOS function. Mitochondria are organelles formed by two membrane layers with different compositions of lipids and proteins, separated by an intermembrane space. Mitochondrial OXPHOS is constituted by three major processes acting in coordination and ultimately determined by ATP synthase activity: nutrient and fuel oxidation; electron transport chain and cytochrome c oxidase activity; and mitochondrial ATP synthase activity. Mitochondrial dynamics control mitochondrial architecture. Increased mitochondrial fission and decreased fusion lead to fragmentation of the mitochondrial network. Mitochondrial morphology and dynamics control mitochondrial degradation via mitochondria-specific autophagy, in part by constantly mixing and reorganizing the mitochondrial content distribution, but also by generating small fission products that can be eliminated by mitophagy. Peridroplet mitochondria are mitochondria that reside within 0.5 μm of lipid droplets.