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MECHANISM OF ENZYME ACTION

MECHANISM OF ENZYME ACTION - a cell needs substance E It...

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MECHANISM OF ENZYME ACTION 1. Surface of the enzyme molecule contains a region called the active site. This is the part that  "fits" the substrate. 2. A temporary enzyme-substrate complex forms as the substrate fits into the active site. 3. The substrate is changed. This will involve making or breaking of chemical bonds. 4. Changed substrate no longer fits the active site, so it is released. 5. Enzyme molecule is unchanged and can immediately catalyze another reaction.   FEEDBACK INHIBITION This is a control mechanism that allows a cell to adjust the activity of enzymes to keep the  amount of their product at an ideal level. Most substances needed in cells are produced in a series  of reactions called a pathway. Each reaction in the pathway requires a separate enzyme. Example: 
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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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