Year 12 Induction WALT… …you will be doing an activity based on a previous AS Biology ISA This will be a realistic “taste” of what your year 12 lessons will be like. You should take today seriously… …just like you should take your AS lessons seriously. WILF… Based on today’s session, you will be given an assignment to do before you return in September. See slide 13 Please bring your completed assignment with you to the Induction Day in September Sensible students will complete this at the earliest opportunity! Beware: failure to hand in this assignment on 4th September may count against you… …You may as a consequence be refused entry onto the AS Biology course… You will be investigating… The effect of substrate concentration on the rate of an enzyme-controlled reaction Catalase is an enzyme found in many tissues. It catalyses the reaction in which hydrogen peroxide breaks down into water and oxygen. The oxygen is given off as a gas. catalase hydrogen peroxide water + oxygen In this task you will investigate the effect of different concentrations of hydrogen peroxide on the rate of this reaction. Materials: Check list… Hydrogen peroxide 100cm3 of water 5 cm3 of plant extract (catalase) Pipettes or measuring cylinders Five boiling tubes and a rack Marker or chinagraph pencil Forceps Stopwatch Glass rod Petri dish or lid for waste 25 pieces of absorbent card 20 second Round Robin: As a group, repeat from memory your materials… Method 1: Making dilutions… Make up five boiling tubes each containing 40cm3 of a different concentration of hydrogen peroxide. The table shows the volume of hydrogen peroxide and the volume of water to add to each tube. Percentage concentration of hydrogen peroxide Volume of hydrogen peroxide / cm3 Volume of water /cm3 100 40 0 80 32 8 60 24 16 40 16 24 20 8 32 Method 2: Run the reaction… 1. Use the forceps to dip a piece of card into the extract containing the enzyme. Watch the card go darker as the extract soaks in. 2. Remove the card from the extract and shake off any surplus liquid. 3. Drop the card into the boiling tube containing 100% hydrogen peroxide. It should fall to the bottom of the tube. 4. As soon as the card is at the bottom of the boiling tube start your stopwatch. Record on your table the time taken for the card to rise to the surface. Magic? Why does the disc rise to the surface? Method 3: Repeats… 5. Remove the card and put it in an empty Petri dish. 6. Repeat once more with 100% H2O2 7. Repeat steps 1 to 6 for each of the other four concentrations of hydrogen peroxide. Normally you would decide for yourself how many times to repeat the experiment at each concentration of hydrogen peroxide. How many times should you repeat a measurement like this? Discuss… Note: “One repeat” means do it twice! Results table… Percentage of H2O2 (%) Time taken for disc to rise to the surface (seconds) First run Should you do a third (or fourth…) repeat? First repeat 100 80 60 40 20 Once you have the correct number of results for each concentration, what would you do next…? How would you handle anomalous results…? Graph: On white boards… Draw and label axes for the IV & the DV, with units. Using the values below, include approximate scales Plot the values Draw a line of best fit (4 marks) Percentage of H2O2 (%) Mean time taken for disc to rise to the surface (seconds) 100 18 80 40 60 64 40 79 20 107 You should have something like this… All write… Describe and explain this graph (5 marks) AfL: Swap and peer assess… As the concentration of hydrogen peroxide increases, the time taken for the disc to rise to the surface decreases This is an inversely proportional relationship This is because as the amount of H2O2 (substrate) increases, oxygen (product) is produced more quickly The oxygen gas collects more quickly on the disc Causing the disc to rise to the surface in less time Assignment… Using the websites below, create an illustrated fact sheet (preferably A3) on Enzymes. http://www.spolem.co.uk http://www.biologymad.com www.kscience.co.uk/resources/ks5/as/enzymes/enzyme s.doc http://kingsfieldbiology.wikispaces.com/file/detail/Enzym es+KS5.ppt http://www.biology-innovation.co.uk/ Remember you are to hand this in on your next Induction Day in September Thank you and see you in September!