In aerobic respiration, which molecule serves as the final electron acceptor?

In aerobic respiration, oxygen plays a crucial role as the final electron acceptor in the electron transport chain. This process occurs in the mitochondria of eukaryotic cells, where electrons carried by electron carriers like NADH and FADH2 are transferred through a series of protein complexes. As these electrons move through the chain, energy is released, which is utilized to pump protons across the mitochondrial membrane, creating a proton gradient.

Ultimately, at the end of the electron transport chain, the electrons are transferred to molecular oxygen. This step is vital because it enables the continuation of the entire process of aerobic respiration; when oxygen accepts the electrons, it also picks up protons to form water as a byproduct. This not only ensures the production of ATP through oxidative phosphorylation but also prevents the backup of electrons in the transport chain, which would halt respiration if oxygen were absent.

The other options do not serve this critical role in aerobic respiration. NAD+ and FADH2 are intermediates that carry electrons and play roles earlier in the process, while carbon dioxide is a product of the metabolic processes rather than an electron acceptor.