Unformatted text preview: a cell needs substance E. It cannot make this substance directly, in one easy step. However, by the following series of reactions, it can get E if it has substance A available as a starting point. Enzyme # 1 Enzyme # 2 Enzyme # 3 Enzyme # 4 A B C D E When so much E is made that it begins to accumulate, there is no need to keep making more, so the pathway needs to be temporarily shut down. As this extra E accumulates in the cytosol, it comes in contact with Enzyme #1. It attaches to the enzyme molecule and causes allosteric inhibition. This shuts down the entire pathway. As the extra E is used up, the E attached to Enzyme # 1 is released and Enzyme #1 becomes active, which starts up the pathway when E is needed....
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- Fall '09
- Enzymes, #, shut down, enzyme molecule