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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.

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.

Can blood from coronavirus survivors treat the newly ill?

Hospitals are gearing up to test if a century-old treatment used to fight off flu and measles outbreaks in the days before vaccines, and tried more recently against SARS and Ebola, just might work for COVID-19, too: using blood donated from patients who’ve recovered.

The Science of an Extreme Animal Athlete

This video follows biologist Shane Campbell-Staton, who is studying the adaptations that allow deer mice living at high elevations to stay warm and active during the winter.

Scientists rethink Alzheimer’s, diversifying the drug search

When researchers at the University of Kentucky compare brains donated from people who died with dementia, very rarely do they find one that bears only Alzheimer’s trademark plaques and tangles — no other damage. That hard-won lesson helps explain how scientists are rethinking Alzheimer’s.

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.