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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.

Modeling the Structure of DNA

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.

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. 

Lizards in Hurricanes

This activity explores images of anole lizards subjected to strong winds, which serve as phenomena for learning about natural selection and the impacts of extreme climate events.

Lizards in the Cold

This activity guides the analysis of a published scientific figure from a study that investigated how anole lizards may adapt to extremely cold temperatures.


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

Understanding Global Change

This interactive module allows students and educators to build models that explain how the Earth system works. The Click & Learn can be used to show how Earth is affected by human activities and natural phenomena.

Winogradsky Column: Microbial Ecology in a Bottle

This interactive module consists of a virtual Winogradsky column, which can be used to explore the diversity of microbes, microbial metabolic strategies, and geochemical gradients found in sediments.