And this is primarily because by increasing the temperature we give the substrate more energy so that it has more energy to basically overcome that activation barrier. Now, the problem with increasing the temperature high or increasing the temperature continually is our proteins have tertiary structure. And remember that at a high enough temperature, the proteins tertiary structure can break down. And at this point we say the protein is denatured and it no longer functions because the tertiary structure is basically the structure that determines the functionality of that protein. And because enzymes are proteins, we see that eventually the rate of activity of enzymes reaches a certain point at which it has a maximum activity rate. And increasing the temperature past this point will denature or break down the tertiary structure of that enzyme and lower that enzyme's activity sharply.