Which compound connects the first and second complexes of the electron transport chain to the third?

1. Ubiquinone is a soluble electron transporter that connects the first or second complex to the third. 2. It is lipid soluble and freely moves through the hydrophobic core of the membrane. 3. Once reduced, it delivers its electrons to the next complex in the chain. 4. Cytochrome c works one stage later, carrying electrons from the third complex to the fourth. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.4 Oxidative Phosphorylation_