How many complexes make up the electron transport chain?

1. The chain is built from large protein assemblies embedded in the inner membrane. 2. They are labelled with Roman numerals. 3. There are four complexes composed of proteins, labeled I through IV. 4. The aggregation of these four complexes, together with associated mobile accessory electron carriers, is called the electron transport chain. 5. Ubiquinone is one of those mobile carriers, not a complex. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 7 'Cellular Respiration', sections 7.1-7.7_