A medicine is a competitive inhibitor of an enzyme in the body…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A medicine is a competitive inhibitor of an enzyme in the body. Farah says it lowers the maximum rate of the enzyme, so more substrate cannot help. Is she right? Say where the medicine binds, and what happens to the Vmax and to the substrate needed for half the maximum rate.
Need a reminder? The key ideaShow
Each enzyme has an optimum temperature and pH. Cold makes an enzyme inactive; heat denatures it. The rate rises with substrate and levels off at Vmax; Km is the substrate concentration at half of Vmax. A competitive inhibitor looks like the substrate and blocks the active site; more substrate reduces its effect.
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. Where it binds. A competitive inhibitor looks like the substrate and binds in the active site, so it competes with the substrate.
Step 2. More substrate. With much more substrate, the substrate wins the site more often. The effect of the inhibitor fades.
Step 3. The numbers. The Vmax is the same if enough substrate is added. The substrate needed for half the maximum rate, the Km, is higher.
Answer: Farah is wrong. The medicine binds in the active site, more substrate does help, and only the substrate level needed for half the maximum rate goes up.
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