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This is an investigation to show how the surface area of a potato affects the breakdown of hydrogen peroxide.

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BIOLOGY INVESTIGATION SKILL AREA P: PLANNING Background Information: Enzymes such as catalyse are protein molecules. Enzymes are used to speed up specific reactions, such as in living cells. They are all very specific as each enzyme just performs one particular reaction. Catalyse is an enzyme found in food such as potato and liver. It is used to remove hydrogen peroxide from the cells. Catalyse speeds up the breakdown of hydrogen peroxide into water and oxygen. This is an investigation to show how the surface area of a potato affects the breakdown of hydrogen peroxide. *Hydrogen Peroxide( H O ) is a colourless liquid, which readily decomposes to give water and oxygen. Hydrogen Peroxide -------------------- Water and Oxygen 2H 0 -------2H O + O *This shows us that when hydrogen peroxide has reacted with the catalyst this is what it produces. There are many ways in which the amount of oxygen could be affected. I believe that the variables that I could change in this investigation are as follows: surface area of the chip (potato), type of potato used e.g. pureed. Mass of potato chip, time left for collisions between potato and hydrogen peroxide, the pH, the temperature of liquid that is reacting, the concentration of hydrogen peroxide or the volume used are going to be major variables in this experiment. ...read more.


Inside cells, most enzymes work best in neutral conditions around pH 7. However, the enzymes in our stomach work best in acidic conditions. So if the pH changes the enzyme's active site changes shape, reforms, meaning that the substrate (H O ) is unable to fit and collide. As a result, the enzyme will cease to function as a catalyst. So breakdown of H O will not occur. To ensure a fair test all experiment will be conducted using the same pH of hydrogen peroxide. I will need a variety of equipment in order to do an accurate experiment. Below is a list of the equipment I will need: -stop clock (timer) -ruler -balance (to measure mass) -Scalpel -potato borer -2 clamp stands -PH probe -goggles -delivery tube -Beaker -thermometer - pen and paper to record results -Disposable gloves -bung - 2 bottles of H O solution. -1 tube rack -elastic band -burette -1 ceramic tile -measuring cylinder -5 x 12cm potato cylinders each from (5 whole potatoes) Diagram to show my Equipment Set-Out (figure 2) To ensure full safety of this experiment I have to make sure that the cork borer and scalpel are used on a tile and not on my hand when cutting the potato cylinders. Hydrogen peroxide is very corrosive so if any of it is spilt onto any area of my skin I must wash that area immediately. ...read more.


Almost immediately I will place the bung on top of the test tube. From the equation at the start I knew that this reaction will produce H O, this will stay in the test tube but the oxygen will pass down the delivery tube and up into the burette as tiny bubbles, which will hopefully displace the water there. I will measure the volume of oxygen in cm evolved in a time of 2 minutes then later on at 4mins, reading the scale on the burette. Making sure I stop the stop clock at the interval and do not reset it. During my trial experiment I decided to just record for 2 minutes but I realised that not enough time was given for collisions to occur, this would lead to unreliable results. I will repeat all the tests at least three times so that an average can be obtained. Repeating the experiments several times will help to produce better and more accurate results, as any inaccuracies in one experiment should be compensated for by the other experiments. This gives the rate in cm of oxygen produced in the time of 2 and 4 minutes, this is because I am timing how much oxygen gas is given off in the space of 2 and 4 minutes for the various surface areas(mm ). From these results, a graph can be plotted with surface area(mm ) on the x-axis and the volume of gas(cm ) on the y-axis. ...read more.

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