A Level Biology Revision "The Effect of Substrate Concentration and Enzyme Concentration on Enzymes" | Freesciencelessons YouTube Video Summary
This Freesciencelessons video explains how substrate and enzyme concentrations impact enzyme activity. The video begins by explaining that the rate of reaction depends on how frequently substrate molecules collide with the enzyme's active site, relating frequency to the number of collisions per second. It then explains that the rate of the enzyme catalysed reaction increases, until the enzymes active site is saturated, at which point the enzymes are working at their fastest rate, known as Vmax. The video then moves on to how enzyme concentration affects the rate of reaction, and explains that the higher the enzyme concentration, the quicker the rate of reaction, and if you double the enzyme concentration, you double the number of active sites.
Detailed Summary:
Effect of Substrate Concentration
The rate of an enzyme catalysed reaction depends on the frequency of collisions between the substrate molecules and the active site of the enzyme. Frequency means the number of collisions per second.
When there is a low concentration of the substrate, there is a low frequency of collisions between the substrate and the active site. As the substrate concentration increases, the frequency of collisions between the substrate and the active sites increases. This means that the rate of an enzyme catalysed reaction is directly proportional to the substrate concentration.
If the substrate concentration continues to be increased, there comes a point where the rate stops increasing any further. At this point, the enzyme is working at its fastest rate. This is called Vmax. At any given time, every active site will be colliding with a substrate molecule. If more substrate is added, there are no free active sites for the extra substrate molecules to collide with, and so, an increase in substrate concentration will not increase the rate of reaction any further. Scientists say that the enzyme is saturated.
Effect of Enzyme Concentration
When there is a low concentration of enzyme molecules, all of the active sites will be colliding with substrate molecules all of the time. A large number of substrate molecules will be unable to collide with a free active site. This means that the rate of reaction will be low.
If the enzyme concentration is doubled, the number of active sites doubles. This doubles the frequency of collisions between the substrate and the active sites, and so, this doubles the rate.
Just like before, the rate is directly proportional to the enzyme concentration, provided that there is more substrate than enzyme. However, if the amount of substrate becomes limited, then increasing the enzyme concentration further will no longer increase the rate. This is because there will not be enough substrate molecules to collide with all of the available active sites.