Where in the cell do the Krebs cycle and electron transport chain occur?

The Krebs cycle occurs in the mitochondrial matrix, the innermost compartment of the mitochondrion, where enzymes for the cycle are located. The electron transport chain, in contrast, is embedded in the inner mitochondrial membrane. This spatial separation allows the products of the Krebs cycle, NADH and FADH2, to feed electrons directly into the chain for energy production.