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 second of three 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 first of three animations about cellular respiration.

This animation shows how the proton gradient across the mitochondrial membrane powers the ATP synthase enzyme to make ATP. It is the third of three animations about cellular respiration.

This three-part animation series explores the biology of the virus SARS-CoV-2, which has caused a global pandemic of the disease COVID-19.

This multipart animation series explores the process of photosynthesis and the structures that carry it out.

This animation shows how mutations in an ion channel protein lead to the genetic disease cystic fibrosis. The animation also discusses how research on this protein has been used to develop treatments for the disease.

This animation shows how termite mounds can increase the productivity of African savanna ecosystems.

This animation illustrates the main stages of the water cycle in Gorongosa National Park, an ecosystem that experiences both wet and dry seasons.

This animation describes how skin color is generated by skin cells as protection against ultraviolet (UV) radiation.

This animation shows how transcription factors find their binding sites in real time. It is based on data from an imaging method that can track single molecules in a living cell.

This animation zooms into a coral reef to explore the tiny animals that build reefs, the photosynthetic algae inside their cells, and the damaging process of coral bleaching.

This animation shows how a region of the brain called the cerebral cortex develops in a human fetus.