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Factors affecting the activity of an enzyme

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Introduction (Planning A) General background: In order to convert substrate into product and for a reaction to occur, enzymes must collide with and bind to the substrate at the active site. The rate at which substrates bind to their respective enzymes could be affected by a number of factors, such as the pH of the reactants, concentration of enzymes and concentration of substrates. Temperature determines the amount of kinetic energy of the molecules in a system where an increase in the temperature of a system results increases in the kinetic energy of the system. The higher the temperature of a system, the higher the levels of kinetic energy of particles, the greater the number of collisions of enzyme and substrate, thus the greater the amount of enzyme activity. However, if temperatures increase beyond certain limits (depending on the enzyme), excess heat supplied will cause the polypeptide bonds that determine the three dimensional shape of active proteins to be broken. This could lead to thermal denaturation of the protein as the specific shape of the enzyme's active site is changed and the substrate can no longer fit into it for the enzyme to function. Thus too much heat can cause the rate of an enzyme catalyzed reaction to decrease because the enzyme becomes denatured and inactive. ...read more.


Data Collection Quantity Unit Uncertainty Instrument used Temperature of hydrogen peroxide �C +/- 1 Alcohol thermometer Mass of potato sample g +/- 0.004 Electronic balance Height of foam/bubbles cm +/- 0.1 Ruler Table 1.1: Summary of quantitative data. Trial Temperature of hydrogen peroxide (�C) Mass of potato sample (g) Height of foam/bubbles (cm) 1 5 2.053 4.9 2 15 2.002 5.6 3 25 2.042 6.8 4 35 2.045 6.3 5 45 2.041 4.5 6 55 2.033 3.1 7 65 2.010 1.9 Table 1.2: Summary of results detailing height of foam/bubbles produced from approximately the same mass of potato across a range of temperatures. Regardless of the temperature at which the hydrogen peroxide samples were, all trials were observed to have a similar reaction when potato samples were added into the test-tube. Bubbles formed around the potato and the hydrogen peroxide became milky with foam; these effects were observed in a short space of time at 25�C and 35�C and longer towards the extreme temperatures of 5�C and 65�C. There were no reactions observed in the test-tubes without potato samples in the experimented range of temperatures. Data Processing and Presentation Graph 2.1: Relationship between temperature of substrate (independent variable) and height of foam/bubbles and therefore the amount of enzyme activity (dependent variable). Temperature of hydrogen peroxide (�C) Height of foam/bubbles (cm) ...read more.


Therefore, a better notion of total products obtained from the reaction can be explained, allowing for a more accurate comparison of evaluation of results to my initial hypothesis. With reference to Graph 2.1, the trend of enzyme activity increasing with temperature until an optimum of 25�C, only to fall rapidly at temperatures higher than this can be established. This is further substantiated by the compound percentage change in enzyme activity as seen in Table and Graph 2.2 as the percentage of reduction in the rate of enzyme activity falls with the increasing temperatures. The controls served in qualifying that as there were no reactions observed in the test-tubes without potato samples in the experimented range of temperatures, temperature is therefore deduced to have an effect on the rate at which the enzyme activity was carried out. The effects of varying temperature on the rate of enzyme activity in potato cells has been determined by measuring the amount of foam and bubbles produced and offers some insight into the amount of enzyme activity. My hypothesis that enzyme activity in plant cells would be low at temperatures lower and higher than an optimum has also been supported to an extent. This has been accomplished by varying the independent variable (the temperature of hydrogen peroxide) to influence the dependent variable (amount of enzyme activity) while maintaining the controlled variables in an attempt to make this a fair experiment. ...read more.

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