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 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.

In this activity, students build a paper model of DNA and use their model to explore key structural features of the DNA double helix. This activity can be used to complement the short film The Double Helix.

In this activity, students engage with an example from the Serengeti ecosystem to illustrate the exchange of nutrients between plants, animals, and the environment. 

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

This interactive module allows students to collect and analyze data from a virtual river to construct biomass and energy pyramids.

This activity guides the analysis of a published scientific figure from a study that investigated how salt affects the electron transport chain.

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 short video explores how the symbiotic relationship between certain plants and fungi allows these organisms to survive in very hot temperatures.

This activity explores the content presented in the animated video How Tube Worms Survive at Hydrothermal Vents, which tells the story of the symbiotic relationship between the giant tube worm and chemosynthetic bacteria.

This activity accompanies the video Seed Dispersal and Habitat Fragmentation. Students use data from published studies to understand patterns of seed dispersal and apply these ideas to the design of a conservation area.