Mitochondria have both an inner and outer membrane. The inner membrane is folded into cristae, and contains electron transport systems and oxidative phosphorylation. This is where ATP synthesis occurs.

The region enclosed by the inner membrane is termed the matrix. This is where pyruvate is dehydrated, forming acetyl CoA, and where the citric acid cycle takes place.

Ribosomes are located in three places in the cell, one of which is the mitochondria. They are also present on the surface of the endoplasmic reticulum, and in the cytoplasm.

Stacked thylakoid membranes are not present in mitochondria. They make up the granum within plastids, such as plant chloroplasts, and are involved in photosynthesis. Here they have a similar function to the inner mitochondrial membrane. This is where the ATP synthase is located in plants.