Enzymes have an active site - Substrates don't.
The substrate is a complementary shape to the active site NOT the "same shape"
Enzymes reduce the activation energy for a reaction to occur
Anabolism is making, Catabolism is breaking
Increasing temperature increases the kinetic energy of everything...substrate, enzyme, atoms that make up the enzyme.
Enzymes are proteins with a delicate tertiary structure whose shape is the resultant of all of the interactions between the amino acids. Some of the interactions are weak bonds which are broken by altering the environment (ph/temperature) of the amino acids.
4 variables control an enzyme experiment - Temperature of the solution, pH of the solution, Enzyme concentration, Substrate concentration. If one is the independent variable - the others MUST be controlled variables. Change one, keep the others the same.
Rate is 1/t where t is the time taken for something to happen, use seconds, never minutes.
You always plot INITIAL rate of reaction because as soon as you add the enzyme to the substrate, the substrate concentration will fall - because it is being turning into product.
pH is a logarithmic scale - pH 4 is 10x more acid than pH 5 and 100x more acid than pH 6, therefore what appears to be a small change in pH is a big change in the number of Hydrogen ions present.
"It is denatured" is not an explanation, you must explain the changes that occur in the enzyme as a result of temperature or pH and the consequences of the changes to the active site and why this prevents catalysis.
The optimum temperature for an enzyme will differ according to the environment in which the organism has evolved to live. What is optimal for an arctic fish will be very different from a bacteria in a hot spring in Yellowstone park.
When explaining enzyme graphs look at the axes, and then look at them again. Then repeat. DO NOT ASSUME YOU ARE LOOKING AT A RATE GRAPH. When explaining graphs, refer to the changes in the dependent variable - don't just say rate.
Competitive inhibitors have part of the molecule which is complementary to part of the active site.
Non competitive inhibitors reduce the concentration of working enzymes.
Hope this has helped a little - if there are any that you would like to add then please drop me a line.