Abiologist wants to increase the rate of his chemical reaction but has a limited amount of enzyme. he continues to increases the substrate concentration instead. eventually, the reaction rate levels off, and he can't get it to go any faster. what prevented the rate from increasing further?

The enzyme has effectively becomes saturated.

Explanation:

Increasing substrate concentration increases the reaction rate this is because more substrate molecules will collide with enzymes molecules so more product will be formed, but at a point any increase in concentration will have no effect on the rate of reaction because substrate concentration will no longer be the limiting factor.