Where do all the stages of respiration (aerobic and anaerobic) happen?

The first part of aerobic respiration is to convert glucose into pyruvate in a series of reactions known as glycolysis, which happens in the cytoplasm of cells. Glycolysis consumes 2 molecules of ATP and produces 4 by substrate-level phosphorylation, giving a net gain of 2 ATPs, whilst also generating 2 molecules of NADH. The pyruvate molecules from glycolysis can go into one of 2 pathways - anaerobic fermentation or the link reaction if oxygen is present. Anaerobic fermentation also happens in the cytoplasm of the cell and produces 2 molecules of lactic acid while regenerating 2 molecules of NAD+.If oxygen is present, pyruvate molecules will undergo the link reaction in the matrix of the mitochondria in the cell. This combines pyruvate with a molecule of coenzyme A to produce acetyl-CoA (which can enter the Krebs Cycle), NADH and carbon dioxide as a byproduct. The acetyl-CoA enters the Krebs cycle which also takes place in the mitochondria to produce lots more electron carrying molecules - NADH and FADH2 to go to oxidative phosphorylation in the inner mitochondrial membrane. Overall, producing around 38 molecules of ATP.