Ritu heats a solution of an enzyme until it stops working…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Ritu heats a solution of an enzyme until it stops working. A test shows that the chain of amino acids is not broken and that its sequence is unchanged. Explain why the enzyme still has no activity, using the active site. Will the enzyme work again if she cools it?
Need a reminder? The key ideaShow
An enzyme is a biological catalyst, almost always a protein. The substrate fits the active site: E + S gives ES, then EP, then E + P. The activation energy is the energy needed to reach the transition state. An enzyme lowers it and does not change the energy of the substrate or the product.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. What heat does. The fold of the chain, its tertiary structure, is held by weak bonds. Heat breaks them, so the chain unfolds. The sequence of amino acids stays the same.
Step 2. The active site. The active site is a pocket made by the fold. When the fold is lost, the pocket is lost, so the substrate can no longer fit and bind.
Step 3. Cooling. The enzyme has been denatured. Cooling does not bring back the fold, so the activity does not return. This is different from an enzyme kept cold, which is only inactive.
Answer: the sequence is intact, but the active site has been lost with the fold. Cooling will not restore it.
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