Figure 1. Mitochondrial architecture.

Figure 2. Oxidative phosphorylation – physical organization of the components of the electron transport chain and the chemiosmotic proton circuit. As electrons (derived from NADH or FADH₂) are transported down the chain (green line), protons are being pumped from the matrix to the cytosolic side of the inner mitochondrial membrane, thus establishing a proton gradient. This gradient may be used by the ATP synthase to form ATP, or it may be dissipated via the proton leak pathway, thus generating heat.

Figure 3. Integration of cytosolic and mitochondrial pathways. The citric acid cycle has integrative functions in a complex network of cellular biosynthetic and degradative processes. A cell may derive energy (in the form of ATP) from different carbon sources including carbohydrates, amino acids (proteins) and lipids. Conversely, breakdown products and intermediates of oxidative metabolism may be used for biosynthetic pathways.