This animation shows how the enzyme complexes of the electron transport chain harvest energy from cofactor molecules to pump protons across the mitochondrial membrane and establish a chemical gradient. It is the fourth of six animations about cellular respiration.
This animation shows the reactions of the citric acid cycle, which splits off carbon atoms and generates energy-rich reduced forms of cofactor molecules. It is the third of six animations about cellular respiration.
In this video, biologist Ken Dial demonstrates that birds use their wings for more than just flying, which may help us understand how dinosaurs used their small wing-like limbs before the evolution of flight.