Enzymes

Enzymes We have previously learned that enzymes are protein catalysts We also learned the chemical that is being acted upon by an enzyme is called the substrate Today we are going to dive deeper into what an enzyme does, how it functions and why it is so important to a cell

Enzymes Both catalysts and enzymes work by lowering activation energy Activation energy is an energy barrier that must be overcome for reactions to proceed You may see them notated as EA

Enzymes Enzymes lower the activation energy needed for a reaction to take place This is a great thing for your cells because it allows reactions to happen faster and with more complete results

Enzymes Take a look at the reaction to the left The pathway in red requires a large amount of activation energy The pathway to the right requires less than half of the activation energy needed to start the reaction

How Do Enzymes Work? How do enzymes work? How do they lower activation energy? Is it magic?

How Do Enzymes Work? Enzymes bend chemicals into unstable positions The bonds from the substrate bend to a highly unstable angle and can be much more easily broken

Video PLEASE DO NOT WATCH UNLESS YOU ARE NOT SQUEEMISH!!! Someone breaks their humerus in the second video It is not humorous It is quite alarming… but it demonstrates a very valid scientific point You have been warned… http://www.youtube.com/watch?v=ucM9qEk1pIc http://www.youtube.com/watch?v=3_z2a7xxKVU

How Do Enzymes Work? The area when an enzyme binds with a substrate is called the active site The substrate must fit very specifically into the enzyme’s active site If it does not fit specifically then the enzyme does not work If the substrate does not fit into the active site, the bonds will not be bent in the correct fashion

Sucrase One good example of an enzyme and substrate is the enzyme sucrase Sucrase is an enzyme that works on the molecule sucrose Notice its –ase ending That designates it as an enzyme

Sucrase

When Enzymes Don’t Work Enzymes are very specifically shaped If their active site changes shape, they cannot function as effectively as normal This means that anything that changes an enzymes shape will cause it to be less effective

When Enzymes Don’t Work Heat, pH and other factors can denature enzymes Denaturing an enzyme is when you change the active site of that enzyme Enzymes are mostly specifically designed to work in the environment that they are in

Other Enzyme Fun… Sometimes enzymes can be stopped This is called enzyme inhibition This can happen if a competitive molecule blocks the active site through competitive inhibition It can also happen if a noncompetitive inhibitor blocks the enzyme from doing its job

Other Enzyme Fun… Some enzymes need help This help comes from cofactors Cofactors are things like zinc, iron and copper that help bend the active site to fit the substrate