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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.

Biology of SARS-CoV-2

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.

Mystery of the Missing Tusks

This activity explores images of elephants with and without tusks, which serve as phenomena for learning about selection and human impacts on the frequency of traits within populations.

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.

Red Tattoo

This activity explores an image of tattoo ink particles inside cells, which serves as a phenomenon for learning about the structure and color of human skin.

Coloration in Vertebrates

This activity explores images of animals with a mutation that affects coloration, which serve as phenomena for learning about skin color genetics and evolution.

Photosynthesis

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

Developing an Explanation for Tuskless Elephants

This activity builds on information presented in the video Selection for Tuskless Elephants. Students use scientific evidence and reasoning to construct an explanation of and develop an argument for tusklessness in elephant populations.