Slow step in reaction mechanisms

[Joanna Pham - 2D]

does anyone happen to understand why the slow step determines the rate?

[Aria Soeprono 2F]

The slow step is the rate-determining step because a reaction can only be as fast as the slowest part. I like to think of it like a factory, where each step in the assembly line helps put together a product. This isn't a perfect analogy, but the production is limited by the step that takes the longest to perform. Likewise, the rate of the reaction is determined by the step that has the highest activation energy, or takes the longest amount of time.