Explain how substrate concentration affects the rate of an enzyme-controlled reaction?

Question

Explain how substrate concentration affects the rate of an enzyme-controlled reaction?

Answer 1

The rate of an enzyme-catalysed reaction shows a curved dependence on substrate concentration. As the substrate concentration increases, the rate increases because more substrate molecules can collide with enzyme molecules, so more reactions will take place. At higher concentrations the enzyme molecules become saturated with substrate, so there are few free enzyme molecules, so adding more substrate doesn't make much difference (though it will increase the rate of E-S collisions).

The maximum rate at infinite substrate concentration is called Vmax, and the substrate concentration that give a rate of half Vmax is called Km. These quantities are useful for characterising an enzyme. A good enzyme has a high vmax and a low Km.  

http://www.biologymad.com/master.html?http://www.biologymad.com/Enzymes/enzyme...

Answer 2

The higher the concentration, the higher the rate, up to a certain point. From a certain concentration onwards, the rate remains constant, because every enzyme molecule is tied up in the reaction. Some molecules must react before the next ones can reach the enzyme and react. At this point, the reaction is substrate saturated.

Answer 3

Substrates are entities upon which enzymes react to bring about a desired reaction. So how does the concentration affect the reaction? Well, its simple, isn't it. The more substrate you have, the longer the reaction can last. If theres too little substrate, the enzyme has nothing to work with, and the reaction stops.

Answer 4

Think of it like throwing darts at a target:

Darts = Substrate

Bulls eye = Enzyme

Outside of bulls eye = Cell wall (in some cases)

The more darts (higher substrate concentration), the bulls eye will be hit more (more product being formed from the enzymes). If only a couple of darts are thrown, then the rate of you hitting the bulls eye will be small (slow reaction), and if lots of darts are being thrown, the rate will increase.

Hope that analogy helps!