A Study of Ppo Activity in Bannas

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ABBEY GRANGE CE ACADEMY An investigation into polyphenol oxidase and enzymatic browning An A2 chemistry investigation William Houghton 22/11/2013 A2 Chemistry Investigation Contents Plan: 2 Aim: 2 Background: 2 The rate equation and rate determining step 5 Method: 8 Methodological background 8 My Method 11 Preliminary work 13 Risk Assessment: 14 References: 15 Analysis 16 PPO study: 16 Catechol study: 19 Temperature study: 21 Plan: Aim: I aim to: Investigate the effect of reactant concentration on the rate of enzymatic browning due to polyphenol oxidase in order to find the order of reaction with respect to each reactant and thus find the rate equation for this reaction Investigate the effect of temperature on the rate of enzymatic browning due to polyphenol oxidase in order to find the activation enthalpy of this reaction Investigate the effect that conditions such as pH and the presence of inhibitors have upon the rate of enzymatic browning due to polyphenol oxidase Background: When a fruit such as a banana is physically damaged it will ‘bruise’ or turn brown. This is due to an enzymatic reaction where a chemical called catechol (a benzene ring with two phenol groups in positions 1 and 2, which can be systematically named as 1,2-benzenediol and has a molecular weight of 110.) undergoes enzyme catalysed oxidation to form a quinone. Quinone is a cyclic organic compound containing two C=O groups. I will be making ortho-quinone (or 1,2-benzoquinone)The oxidation reaction that starts the browning process is outlined below. The chemicals involved in this reaction are catechol, quinone and the enzyme polyphenol oxidase. Once quinones are formed they then rapidly polymerise to form dark brown melanin pigments. Enzymes such as polyphenol oxidase are huge protein structures. Proteins are made up of long chains of

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