C1.1.15 Competitive inhibition (HL) Notes

Competitive Inhibition Reduces Rate of Enzyme Activity

1. Competitive inhibition is like when you're trying to charge your phone but someone keeps beating you to plugging in a cable, except it isn't connected to power at all.
2. While their useless cable occupies the port, your real cable can't get in.
3. The inhibitor (fake cable) fits the enzyme's active site (charging port) but can't be processed, blocking real substrate molecules from binding.
4. And since only one molecule fits at a time, more inhibitors mean fewer productive reactions.
5. The enzyme isn't broken, it's just wasting time on molecules that look right but don't work.

How Competitive Inhibition Works

1. In this type of inhibition, the inhibitor has a molecular shape similar to the substrate, allowing it to bind to the enzyme's active site.
2. As the inhibitor occupies the active site, it prevents the substrate from binding, leading to a slower rate of reaction.
3. The binding of the inhibitor is reversible, meaning that if the concentration of the substrate increases sufficiently, the substrate can outcompete the inhibitor for access to the active site.
4. Therefore, increasing the concentration of the substrate can reduce the impact of competitive inhibition.

The Role of Substrate Concentration

1. The effectiveness of competitive inhibition depends on the relative concentrations of the substrate and the inhibitor:
   1. Low Substrate Concentration: Inhibitors have a higher chance of occupying the active site, reducing the rate of reaction.
   2. High Substrate Concentration: The substrate outcompetes the inhibitor for the active site, diminishing the inhibitory effect.