Explain the difference in the rates of reaction at 60 °C and 37 °C between 20 and 40 minutes.

"A technician investigated the effect of temperature on the rate of an enzyme-controlled reaction. At each temperature, he started the reaction using the same concentration of substrate. Explain the difference in the rates of reaction at 60 °C and 37 °C between 20 and 40 minutes."

At 20 minutes and 40 minutes the concentration of product remains same for 60 degrees due to the high temperature causing the enzyme to denature. This means the shape of the active site changes so that no more enzyme-subtrate complexes can be formed so there can be no further increase. 

There is continuing increasing concentration of product at 37 degrees as the enzyme does not denature at this lower temperature and there is still substrate available. Therefore, enzyme substrate complexes can continue being made to be converted to product.