This video will serve as an introduction to enzymes. Enzymes are proteins and they are one type of biochemical catalyst. The figure to the left is a rendering of an actual protein. This gives you the sense of how large these molecules are. The figure to the right is a much more simplified representation of an enzyme. It is the lock and key model typically shown in a biology class. As a reminder, catalysts or enzymes in this case facilitate a reaction by lowering the activation energy of the reaction. Many of the reactions in our body would not occur if it weren't for the enzymes that catalyzed them. Enzymes are commonly named after the reaction they catalyze. There are six major groups of enzymes. Oxio reductases, transferases, hydrolysis, liases, isomerases, and ligases. We'll take a closer look at each of these. Oxio reductase catalyzes reduction oxidation reactions. Here we see the pyruvate molecule being reduced because of the addition of hydrogen to the oxygen of the C double bond O. The fact that the carbon double bond to the oxygen is changed to a carbon single bond to the oxygen. The NADH molecule was oxidized because it became NAD plus and lost the hydrogen. Transferase involves the transfer of a functional group. In this case, we see the transfer of an NH3 group and a C double bond O group. Hydrolysis catalyzes hydrolysis reactions. Hydrolysis reactions involve water and water breaking a molecule into two. Typically, hydrolysis reactions occur with esters and the ester bond is broken. Liase helps catalyze the formation of double bonds or the addition to carbons of a double bond. This is very similar to the addition reactions we learned when we studied alkene. In this case, we're adding water to the double bond to form an alcohol. A somerase facilitates the production of an isomer. Take a few minutes and verify that the molecule on the left and the molecule on the right have identical formulas. And finally, ligase. This enzyme helps catalyze the joining of molecules. Here's a better example showing the function of ligase. Proteins or enzymes lose their functionality and change their shape as pH and temperature change. When a protein or enzyme is exposed to non-optimal pH or temperature conditions, the protein or enzyme is said to have been denatured. Temperature influences enzyme activity because the shape and the intramolecular attractions of large protein molecules changes with temperature. If the shape and the intramolecular attractions are altered because of temperature, a substrate cannot fit into the enzyme, therefore not catalyzing a reaction. In general, the human body is maintained at 98.6 degrees or approximately 37 degrees Celsius. In this graph, illustrates that optimal enzyme activity occurs at 37 degrees C. pH also influences enzyme activity. Enzymes will take on different shapes and have different intramolecular attractions with different pHs. There is not one overall pH for optimal enzyme activity. Optimal activity for pepsin occurs at pH 2, which is much lower than a pH for optimal activity for tripsin, which is at pH 8.