Enzymes BHASVIC biology

Initially, from 0 to 10 degrees, the temperature is very low and so the substrate has less kinetic energy. This means that less collisions happen with the active sites of enzymes, less enzyme-substrate complexes are formed therefore rate of reaction is slow. From 10-40 degrees, the rate increases rapidly and the rate of reaction is directly proportional to temperature. 
The substrate has increasing amounts of kinetic energy which makes collisons with the active site more likely, more enzyme-complexes will be formed resulting in an increase in rate. After 40 degrees, the rate of reaction is indirectly proportional to temperature. The rate decreases because the enzyme is denatured at higher temperatures. The large amounts of kinetic energy breaks the hydrogen bonds holding the tertiary structure of the enzyme in place. The active site will change shape and, as a result, the substrate will no longer fit, catalysation won't take place and enzyme-substrate complexes can't be formed.

The graph below shows the energy changes that take place during a chemical reaction without an enzyme catalyst.Explain how the presence of an enzyme catalyst would change the shape of this graph.

The activation energy (energy needed to start the reaction) would be significatly less.Enzymes reduce the activation energy through a process called catalysis. Enzymes can use the transfer of protons or electrons to the reactants to make them easier to catalyse, therefore meaning they need less activation energy for the reaction to occur. 

Suggest if the reaction is endo- or exothermic and give a reason why. 

The reaction is exothermic as the energy at the end product is lower than it was initially, which means energy was lost whilst the reaction took place rather than gained like in endothermic reactions.