Cells are almost like tiny factories run by robots, with the nucleus, DNA, proteins, lipids, and vitamins and minerals all playing critical roles. George Zaidan and Charles Morton lay out the blueprint of a cell and explain how biochemistry binds all life together. [4:01]

Explains oxidative phosphorylation, which is the fourth step of cellular respiration, and produces the most of the energy in cellular respiration.

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All cells, organs and tissues of a living organism are built of molecules. Some of them are small, made from only a few atoms. There is, however, a special class of molecules that make up and play critical roles in living cells. These molecules can consist of many thousands to millions of atoms. They are referred to as macromolecules (or large biomolecules).

Students learn how viruses invade host cells and hijack the hosts' cell-reproduction mechanisms in order to make new viruses, which can in turn attack additional host cells. Students also learn how the immune system responds to a viral invasion, eventually defeating the viruses -- if all goes well. Finally, they consider the special case of HIV, in which the virus' host cell is a key component of the immune system itself, severely crippling it and ultimately leading to AIDS. The associated activity, Tracking a Virus, sets the stage for this lesson with a dramatic simulation that allows students to see for themselves how quickly a virus can spread through a population, and then challenges students to determine who the initial bearers of the virus were.