Two Paths

[Allen Guo 4A]

Enzymes can lower the activation energy, but doesn't the reaction still occur without using the enzyme, meaning there are multiple paths?

[PaigeBlack]

yes. while the reaction could still occur without the enzyme, the enzyme lowers the activation energy and creates a new path for the reaction to occur on.

[lindsay lathrop 2C]

Yes there are multiple paths, the original reaction may still continue next to the catalyzed reaction but the rate is determined by the faster path (as it governs the overall rate of formation of products). The slow rate determining elementary reaction will not control the rate if it can go through a faster step on another path.

[Amy Zheng 2l]

Yes there are multiple paths

[Clarissa Molina 1D]

When there are multiple paths, why is the faster one the one that determines the rate law? I'm still kind of confused on this concept

[Evelyn L 1H]

The slow step is the rate-determining law, not the fast step. If it is the slowest step, the entire reaction must wait for it, then it is the rate-determining step. Dr. Lavelle used the example of the bottleneck/funnel neck effect to describe this.
Here is a helpful analogy I found:
The rate determining step can be compared to the neck of a funnel. The rate at which water flows through a funnel is limited/ determined by the width of the neck of the funnel and not by the rate at which the water is poured into the funnel. Like the neck of the funnel, the slow step of a reaction determines the rate of a reaction.