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The aim of this investigation is to find out what effect pH has on the enzyme Catalase in it breaking down Hydrogen peroxide into Oxygen and Water.

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Introduction

The effect of pH on the activity of Catalase Aim: The aim of this investigation is to find out what effect pH has on the enzyme Catalase in it breaking down Hydrogen peroxide into Oxygen and Water. Planning: Before going any further, we need to find out several things such as, what provides a good source of the enzyme Catalase, things about enzymes in general as in what they are, what they do, what things effect enzymes, the structure of enzymes etc. The enzyme Catalase is found in the human body as well as potatoes, apples, liver and several other things. So what are enzymes? Enzymes are biological catalysts. They speed up chemical reactions in all living things, and allow them to occur more efficiently. Although they work powerfully, enzymes are chemical molecules, made up of proteins. Each particular enzyme has its own unique, three-dimensional shape shared by all of the same type of molecules. Within this shape is an area which is the active site where the chemical reactions take place. There are two main types of enzymes: * Intracellular enzymes- which control reactions that happen inside cells * Extracelular enzymes-which control the chemical reactions that occur outside cells, for example. Digestive enzymes work outside cells in the gut. Enzymes help to turn the substrate into the product. The active site in the enzyme helps it to recognise its substrate in a very specific way. Just like a key only fits into a specific lock, each enzyme has its own specific substrate. This is called the lock and key theory. Factors: There are several factors which affect the way an enzyme such as Catalase works. Every enzyme has optimum conditions they work best in because enzymes are very sensitive. Enzymes work best when they have high enough substrate concentration for the reaction they catalyse. If too little substrate is available the rate of reaction is slowed and cannot increase any further. ...read more.

Middle

This is because each enzyme is especially designed to break down one particular substrate; this can be explained by a theory called the lock and key theory. The enzyme is designed in such a way that the one particular substrate fits perfectly into the active site of the enzyme just like a lock is designed. Only the especially designed key can fit into that one particular lock. If the structure of the active site is even slightly altered it can affect in the substrate not fitting into it, disallowing it to be broken down. (www.s-cool.co.uk) I predict that the graph will look something like this: The predicted graph shows that as the pH increases the time taken decreases until it reaches pH 7, after pH 7.5 it starts to gradually increase as the pH increases. At the beginning the graph shows negative correlation until it reaches pH 7. It then shows positive correlation as the pH increases further. This is because at the beginning of the graph, the pH is acidic and so as we can see shows that it takes longer for H2O2 to break down but as the pH comes closer to neutral the time taken gets less and less until it reaches neutral pH 7. After that, the pH starts becoming alkaline and so the time taken starts increasing again. This is what I predict will happen. The graph, which shows the amount of pressure produced per second, will look something like this. This shows that pH 7-7.5 produces the most amount of pressure in a second. The two extremes produce the least amount of pressure. I predict that if my previous prediction is correct then the most amount of product will be produced in pH 7-7.5. Analysis: The results show that the enzyme Catalase works best in the neutral pH 7.5. When the pH was too high (alkaline) or too low (acidic) ...read more.

Conclusion

Things like mixing up the pH solution can also lead to anomalous results. Below is the experiment again, but with the changes I suggested to make the results more reliable and accurate. Apparatus: * Bung * Conical Flask * Delivery tube * Pressure Sensor * Stop-watch * Petri dish * Digital balance * 2 Measuring cylinders * pH solution 4, 4.5, 5, 5.5, 6, 6.5,7, 7.5, 8, 8.5, 9 * Hydrogen peroxide (H2O2) * Grated Potato * Syringe * Paper * Pen * Spoon * Grater * Distilled water * Method: * Gather the apparatus e.g. H2O2, pH solution 4, and potato etc * Grate the potato * Measure 3g of potato by putting the Petri dish on to the digital balance and setting it on 0g and then put the potato on the Petri dish until the scale reads 3g * Measure 20cm� of H2O2 with the other measuring cylinder making sure you read from the lower meniscus * Measure 10cm� of pH 4 solution in a measuring cylinder making sure you read it from the lower meniscus * Put the pH 4 solution and H2O2 in the conical flask * Attach the syringe to one of the outlets of the bung * Attach the delivery tube in the other outlet * Set the stop-watch on count-up * Put the grated potatoes into the conical flask with a spoon and immediately close the flask with the bung and while doing this attach the other end of the delivery tube to the pressure sensor * As soon as you've put the tube in the pressure sensor start the clock * Hold the syringe while doing the experiment * Measure the time it takes for the pressure to reach 5KPa and record the time on a table * Repeat the experiment for pH solutions 4.5, 5, 5.5, 6, 6.5,7, 7.5, 8, 8.5, 9. * Before repeating experiment each time, wash the conical flask and the measuring cylinders with distilled water ?? ?? ?? ?? By Kausar Hussain 10S Candidate no. 8410 1 ...read more.

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4 star(s)

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This is a fairly thorough account of a catalase investigation including detailed and correct explanations. Descriptions of variables involved could have been better.

Marked by teacher Adam Roberts 10/05/2013

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