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Effect of Temperature on Rate of Hydrolysation of Pineapples

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Introduction

Investigation to determine whether temperature affects the rate of hydrolysation of bromelain enzymes within pineapples when placed within protein substrates Aim: To investigate the effects of increasing temperatures on pineapples, which contain the enzyme bromelain, and observe the affect on the rate of hydrolysation when placed within gelatine. Scientific background: Gelatine is a common protein used in the manufacture of jelly. It consists mainly of collagen which is a fibrous protein present in all animals. The structure of a protein is made up of a numerous amount of amino acids joined together by the process of condensation as shown in the diagram below. Figure 1.0 Proteins are polymers of amino acids, and these polymers or polypeptides are made up of amino acids in a specific sequence which determines the proteins function. This is known as the primary structure of a protein. The basic structure of these amino acids is shown below. The R groups of the amino acids interact with each other, altering the chain to twist and fold into a three dimensional shape. The length of chains can coil into alpha helices or beta pleated sheets and this is known as the secondary structure. The polypeptide chain then folds to produce a specific 3D shape which forms the tertiary structure. These proteins, as mentioned are made throughout the formation of peptide bonds between amino acid molecules. In order for the bonds formed in proteins to be broken down, the reverse of condensation must occur which is hydrolysis (amide hydrolysis for peptide bonds). The addition of water will allow for the peptide bond to break spontaneously, however this process is very slow and is usually facilitated by the use of enzymes. This rate of breaking the peptide bonds (rate of hydrolysation) can be increased by enzymes that are specific to proteins, called proteases. Enzymes are a form of globular proteins, where the polypeptide chains are folded into compact spherical shapes. ...read more.

Middle

* Leave for 30 minutes. Pineapple juice boiled separate from jelly otherwise the jelly would melt and no results could be collected * Make a hole within jelly using cork borer * Pour 4.71 cm� of juice into the hole * Leave for 24 hours at room temperature * A control dish used that contains only 50cm� of jelly. * After 24 hours, using a syringe remove liquid from Petri dish and measure the amount. * Repeat this process now for the canned pineapples. Controlling Variables: * Use the same jelly for every Petri dish * Use the same section of the fresh pineapple, as some areas may contain more enzymes than others, and use the same tin of pineapples. * All Petri dishes, once the pineapple juice has been added, will be left in the same room in order to know they are affected by the same conditions in this room e.g. room temperature, light * Use a control in order to view the effect of the manipulated variable * The manipulated variable which is temperature can be controlled via the water baths. The room temperature will be continuously monitored using a thermometer for those Petri dishes left in room temperature. * Equal amount of pineapple juice will be used and equal amounts of jelly poured into the Petri dish will be used. * Pineapple juice kept in the required temperature ranges for the same amount of time (30 minutes) * All the jelly is refrigerated in the same fridge at the same level for the same amount of time. Risk Assessment: Below is a risk assessment table that has been constructed in order to view the risks and minimize them. Activity Persons Affected Hazards Harm Caused Risk (Severity x Likelihood) Existing Control Measures Residual Risk (Severity x Likelihood) Boiling tube breakages St, S, PE Glass Cuts to skin 2 x 2 = 4 Wear goggles, clear up glass immediately 1 x 1 = 1 Burning yourself from water baths PE Person can ...read more.

Conclusion

The rate of hydrolysation has been increased until 40 degrees due to higher temperatures giving the enzymes more kinetic energy in order for them to form enzyme substrate complexes at a faster rate and therefore producing more volume of liquid as the protein is broken down. However, the rate of hydrolysation is additionally then slowed down due to the excessive high temperature causing the Bromelain enzymes to denature and no longer function. Denaturing of the enzymes causes the active site on the enzyme to mould and into a disfigured shape not allowing substrate complexes to be formed. Fresh pineapples compared with canned pineapples produce more liquid due to the fact that they have more enzymes to break down the protein into liquid. Evaluation: The investigation has been demonstrated to be successful as the hypothesis was proved correct and the null hypotheses were disproved. The statistical tests showed the relationship between the two variables was present up till a certain point i.e. optimum temperature for enzymes. The procedure used was clearly appropriate as reliable results were collected and valid conclusions were able to be drawn from these results. However, within the graphs it can be seen that there are some results that do not fit the line of best fit or trend exactly. These results are not entirely anomalous but do imply that some human error has occurred. The results are all still within a 95% significance level though. Errors and modification: * On graph 1 at 40 degrees there is a large error margin compared to the rest. These error margins are not large for graph 2. The error margins show the human error that occurred due to misreading the cylinder value. This can be avoided by having a 2nd person reading the measuring cylinder. * The results from Spearmans Rank achieved were very good, but, they were suspiciously good. The values obtained proved the trend to be perfect. This may have been because of the small sample size. To avoid this again, a larger number of temperature ranges should be used so there are more data values. ...read more.

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