The DNA of mitochondria and chloroplasts is typically circular, not linear, and it is not enclosed within a separate membrane inside the organelle. Both organelles are enclosed by two membranes. They also perform phosphorylation: mitochondria carry out oxidative phosphorylation, which is associated with the inner mitochondrial membrane during cellular respiration, while chloroplasts perform photophosphorylation, which is associated with the thylakoid membrane during photosynthesis. In mitochondria, ATP synthase is located on the inner mitochondrial membrane, whereas in chloroplasts, it is located on the thylakoid membrane.