Mitochondria are the cell organelle where aerobic respiration occurs.

Mitochondria have 2 membranes with the inner membrane (cristae) folded.

Cristae: Folded inner membranes increases surface area. Electron transport occurs here.

Matrix: Inner compartment of mitochondria. Contains enzymes for the Krebs Cycle.

Outer Compartment: Space between inner & outer membranes. Area where H+ concentrates.

The 1st step of respiration, Glycolysis, occurs just outside the mitochondria in the cytoplasm.