Enzymes PHOTOSYNTHESIS:CO 2 + H 2 O → Glucose + O 2 RESPIRATION:Glucose + O 2 → CO 2 + H 2 O How do these processes happen? What do the arrows mean? Hmm!! Think about the Photosynthesis and Respiration reactions. → →

Let’s think about Respiration. This process releases energy in all your cells all the time. Think: What would happen if you mix a small spatula of glucose with oxygen (from air) in a test tube.. There is no reaction (no change). What should we do to get it to react? HEAT IT ! – but your cells aren’t that hot! There are special chemicals in all your cells that help reactions to take place – ENZYMES.

Learning Intentions I can state that enzymes are biological catalysts. I can state that enzymes are found in all living cells I can describe the effect of an enzyme on a reaction. I can name the substrate and products of catalase and include this in an enzyme equation

Success Criteria I can carry out an experiment looking at enzyme activity I can identify which variables to control in an experiment. I can design an experiment to test a prediction. I can produce an experimental report, using a framework.

Enzymes Control all chemical reactions Present in all living cells Protein Speed up chemical reactions Remain unchanged Can be reused Specific

Any reaction needs energy to get it started. This shows the energy needed to get the yellow molecule to split into two green ones.

This shows the energy needed to get the yellow molecule to split into two green ones. This time using an enzyme.

Much less energy is needed to get the yellow molecule to split into two green ones, using an enzyme.

Any reaction needs to be “activated” before it can get going. This takes ENERGY – usually supplied as heat. If your cells get too hot what happens ? They will die. What is your BODY temperature? What is your HAND temperature? Enzymes let reactions take place quickly at the low temperature that cells work at. Enzymes help the reaction take place but are not changed themselves. They are an example of a CATALYST.

Hydrogen peroxide and catalyst experiment Set up 2 test-tubes: 1. 10mls Hydrogen Peroxide & 1 spatula of MnO mls Hydrogen Peroxide only. MnO 2 is an example of a catalyst. Watch what happens in both tubes. Write two or three sentences to describe what happened in this experiment.

Why do we have the other tube? To COMPARE the experiment tube with – to show that MnO 2 breaks the peroxide down and not anything else. This is called a Control tube. WRITE a note about why we need a Control tube. Hydrogen Peroxide is a chemical produced in most cells as a waste product in many of their chemical reactions. It is dangerous, it is used as a bleach and in hair dyes. Our cells have to be able to break it down quickly at low temperature. They need an enzyme to help them do this.

Our cells need an enzyme to help them break down Hydrogen peroxide. This enzyme is called Catalase. Hydrogen peroxide Water + Oxygen Catalase

CATALASE IN TISSUES (1) AIM:To see if Catalase from different tissues can break down Hydrogen peroxide. Leave 5 lines blank here PLANNING / METHOD: For this experiment you will be told the method to use. First, think about what you are going to change.

CATALASE IN TISSUES (1) PLANNING / METHOD: We will compare the reaction of 3 different tissues. 1. Cut a thick slice of potato, turnip and carrot. 2. Use a cork borer to cut a cylinder from each slice. Trim each cylinder to 2cm long. 3. Set up 4 test tubes each containing 10mls of Hydrogen peroxide and 2 drops of washing up liquid. 4. Put the cylinders into each tube at the same time and start timing. 5. After 5 minutes measure the height of oxygen foam in each tube.

CATALASE IN TISSUES - REVIEW What happened? How did you write down your results? Are they in: a table with headings and units. If you didn’t do all of these then sort them now!!

CATALASE IN TISSUES - REVIEW Think about the experiment you have just done. What were the variables? What is a Variable? “Something” that can change.

CATALASE IN TISSUES - REVIEW Variables activity There are three types of variable: Independent variable (the one YOU are going to change) Dependent variable (what happens, “the results”). Controlled variables (the ones that must be kept the same for a valid experiment).

Variables activity COLLECT: a set of Variable cards. SORT the cards into the pile for the type of variable that they are. Independent variable (the one YOU are going to change) Dependent variable (what happens, “the results”). Controlled variables (the ones that must be kept the same for a valid experiment). Variables song

CATALASE IN TISSUES - REVIEW This experiment had an AIM, but a good experiment also needs a PREDICTION. The Prediction is worked out before we do the experiment – sometimes it can be a bit of a guess, but that’s OK because it can be changed later. It says what we think is going to happen. It connects the dependent and independent variables Use the dependent and independent variables to work out what the PREDICTION should have been. Now add that to your experiment write up, in the space you left between AIM and METHOD.

CATALASE IN TISSUES - REVIEW The experiment now has: Aim, Prediction, Method, Results…. What else does it need? CONCLUSION This answers the question: “Do the RESULTS match the PREDICTION?” Is there a pattern or trend? Again, you should write about this using the Independent and Dependent variables. Don’t worry if it sounds quite like the PREDICTION.