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Citric Acid Cycle

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.

Electron Transport Chain

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.

ATP Synthesis

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.

Nutrient Cycling in the Serengeti

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

Serengeti: Nature’s Living Laboratory

This film explores the foundational research in the Serengeti National Park, Tanzania, that uncovered many of the ecological principles that govern how animal populations and communities are regulated.

Sodium Channel Evolution in Electric Fish

This activity guides the analysis of a published scientific figure from a study that investigated how gene duplication contributed to the evolution of electric fish.

The Wolves of Isle Royale

This activity explores images of wolves hunting a moose on Isle Royale, which serve as phenomena for learning about predator-prey population dynamics.

Cougars and Trees in a Trophic Cascade

This activity guides the analysis of a published scientific figure from a study that investigated the effects of tourism on cougars and cottonwood trees in a national park.