Which substances are involved as inputs for the electron transport chain?

The electron transport chain (ETC) is a crucial component of cellular respiration, primarily occurring in the inner mitochondrial membrane. It is responsible for the final stages of energy production, where high-energy electrons are transferred through a series of protein complexes. The primary inputs for the electron transport chain are NADH and FADH2, which are reduced coenzymes generated during earlier stages of respiration, such as glycolysis and the citric acid cycle.

These two molecules carry high-energy electrons to the ETC, where the energy from these electrons is used to pump protons (H+) across the mitochondrial membrane, creating a proton gradient. Ultimately, oxygen serves as the terminal electron acceptor in the chain, allowing for the formation of water when electrons combine with protons and oxygen. This process is essential for the production of ATP through oxidative phosphorylation.

The other options do not accurately describe the inputs for the electron transport chain. While glucose, pyruvate, and acetyl-CoA are involved in the earlier metabolic pathways leading up to the electron transport chain, they do not directly participate in the chain itself. Similarly, ADP plays a role in the formation of ATP during oxidative phosphorylation, but it is not considered an input of the electron transport chain like NAD