1. Cells of E. coli bacteria Allow cells to respond to changes in their environment Only make proteins when they are needed

3. http://www.sumanasinc.com/webcontent/animations/content/lacoperon.html

5. http://multimedia.mcb.harvard.edu/anim_inn erlife.html http://www.molecularmovies.com/movies/ber ry_apoptosis.html

6. Differentiated Cells of Humans Allow cells to respond to changes in their environment Only make proteins when they are needed Cell differentiation for specialized structure and function

7. The genes for “housekeeping” enzymes, such as those involved in glycolysis, are active in all metabolizing cells. In contrast, the genes for specialized proteins are turned on only in particular types of cells. In summary, the particular genes that are active in each type of differentiated cell are the source of its particular function and structure.

12. http://www.hhmi.org/biointeractive/media/mecp2-lg.mov

14. http://www.hhmi.org/biointeractive/media/p53-lg.mov http://www.dnai.org/a/index.html

15. http://www.hhmi.org/biointeractive/media/ppar-gamma-lg.mov http://www.hhmi.org/biointeractive/media/ppar-delta-lg.mov

19. http://www.hhmi.org/biointeractive/media/p roteasome-lg.mov

21. http://highered.mcgraw- hill.com/olc/dl/120080/bio31.swf

22. http://www.bio.davidson.edu/courses/Immun ology/Flash/MAPK.html http://learn.genetics.utah.edu/content/begin/ cells/cellcom/