Brief Intro to Enzymes We’re going to move through this ppt quickly At most, jot down a note here and there This is just meant to be a brief introduction to enzymes before we start the lab

Enzymes Biological Catalysts

Enzymes are Biological Proteins Big molecules Many of our genes code directly for enzymes Estimated to be about 75,000 different types in the human body

Enzymes Do….Do Not… Speed up chemical reactions Allow reactions to occur with less energy input Provide energy for the reaction End up altered or used up or in the product Change the net effect of the reaction (the products are the same with or without an enzyme)

Chemical Energy Potential energy Energy stored in the arrangement of bonds Can be converted into kinetic energy forms (heat, light, sound, movement etc.) like a spring

Heat Energy Is how much the atoms/molecules are moving More heat/temperature = more movement

Heat vs. Temperature TemperatureHeat Average kinetic energy of the molecules in a substance i.e. how fast the molecules are moving I.e. in a cup of hot tea the molecules are moving fast- some of them fast enough to turn into a gas! Total kinetic energy of a substance I.e. the ocean has a ton of kinetic energy, even though the water is fairly cold

All reactions require an initial input of energy Something has to get the reaction started Called the activation energy i.e. lighting the fuse on a bomb

Why? It takes energy to get bonds to break More energy = moving faster = molecules can break apart When new bonds form molecules stop moving and release energy

I.e. It takes energy to split lactose and water Energy is released when new bonds are formed Energy Energy

Some reactions are EndothermicExothermic The products have MORE potential energy than the reactants These reactions absorb energy/heat i.e. a ice pack The products have less energy than the reactants Energy/heat is released I.e. TNT

Endothermic vs. Exothermic EndothermicExothermic Net effect is energy into the products Net effect is energy released from reactants

So What Do Enzymes Do? They allow bonds to be broken at lower temperatures Thus they lower the activation energy So reactions can happen more easily with less input of energy (at lower temps)

Enzyme Terminology Substrate = reactant Active site = place on enzyme where the substrate can bind

Enzymes are Specific! Only substrates that “match” the active site can be catalyzed Like a lock and key

How Do They Do it!!!!???? They may arrange the molecules to make it easier for bonds to break or collisions to happen They may change the environment (make it acidic etc.) May temporarily bond with substrate, stabilize the intermediates etc.

Potential Energy Diagram

Enzyme Catalysis Lab You will be testing how different factors affect the rate of an enzyme- catalyzed reaction You will spend the majority of the time designing and implementing your own experiment

Your Experiment Should test how 1 factor affects the rate of hydrogen peroxide decomposition Should include 3 experimental trials and a control trial Should be conducted in a single block period

You Are Writing Your Own Procedure Needs to be thorough! Assumptions make an… out of u. Nothing is too small to put in procedures ▫i.e. put on glasses, rinse cups

Your Procedure Con. Set up your entire experiment at once ▫Don’t say “I will redo steps 1-5” ▫Make all of the catalase you need at once, put it into all the test tubes at once etc. Anything you will need to do should be in the procedure ▫I.e. rinsing cups, measuring amounts of water, how long you let the reaction run etc. Anything you will need to use should be in the procedure ▫i.e. graduated cylinder, scale etc.

Safety No open flames- any heating should be done with a hot water bath Goggles must be worn Gloves must be worn If you are going to test pH precaution must be taken with acids/bases Immediately report any broken glassware!

Steps 1.Complete the prelab individually ▫Write your own preliminary procedure. It can be very rough 2.When approved, write a final procedure as a group ▫This should include ideas from everyone’s procedure and should be completely thoroughly 3.When approved, complete the procedure sheet individually ▫Draw procedure, make list of necessary materials 4.By Tuesday afternoon (I know I don’t have you, come find me or me) give me a final procedure for your group and a list of materials

Examples Use the instructions for preparing the catalase solution as a guideline for how thorough procedures should be

Basic Procedure (written) 1.Using the scale, measure out _g of peeled potatoes 2.Using the mortar and pestle, mash up the _g of potato 3.Using a graduated cylinder place _ml of water into a cup and add the peeled potatoes 4.Thoroughly mix the mashed potatoes and water 5.Keep on ice 6.Using a pipette add 1ml of hydrogen peroxide to a clean test tube 7.Using a different pipette add 1ml of catalase solution 8.Observe and measure ________

Scoring Prelab /5 (individual) Procedure /5 (group) Procedure Sheet/5 (individual) Results/Graphs/5 (individual) Conclusion/10 (individual)

Scoring Continued Any material you have to ask for that wasn’t on your procedure/materials sheet = -1 point Any question you have to ask about your procedure = -1 point No trading of materials between groups. If I see it you both lose a point (i.e. if you don’t identify that you need a scale, you lose a point if you use it)

A Few Notes You will mash your own potatoes to make the catalase solution. As a standard you want to mash about 1g of potato per 2ml of water. As a standard you should react about 1ml of peroxide with 1ml of catalase solution