The Effect on Rate of an Enzyme Catalysed Reaction by Different Objectives

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The effect on rate of an enzyme catalysed reaction by different objectives which include effect of substrate, temperature, ph and effect of a competitive inhibitor phosphate ions. This is determined by the reaction of hydrolysis by p-nitrophenylphosphate (PNP) as a substrate by the enzyme phosphatase. Abstract

The hydrolysis of p-nitrophenyl phosphate has been studied in human red blood cells. To see if hydrolysis was related to the functioning of the sodium pump. Acid phosphatase catalysis’s the hydrolysis of p-nitophenyl phosphate under four different objectives ph, temperature, substrate inhibition and a competitive inhibitor. The phosphatase and PNP were placed in test tubes with different concentration of each but under different objectives. The concentration of the enzyme and substrate were the same for each experiment. It was shown that the Vmax was 0.286 and the Km was 0.0114. As the valve of Km is small this shows that there is a high enzyme substrate affinity. There were some anomalous results obtained within experiment 2 and experiment 3 these may be due to experimental or human errors.

Enzymes are biological catalysts that speed up the rate of reaction between substances without themselves being consumed in the reaction. The catalytic thrive of an enzyme comes from the addition of a substrate binding to a specific region on the enzyme called the active site. May factors oppose on the effect of an enzyme these include temperature, ph, concentration of substrate and competition. All of these factors are investigated in the experiment of PNP with the enzyme phosphatase. Looking at the effect of concentration of substrate for this reaction you would expect that at a constant concentration of phosphatase the reaction rate increases with increasing PNP concentration until it reaches a maximum velocity. At the maximum velocity it suggests all the enzyme phosphatase active sites are occupied by PNP and therefore the reaction rate cannot increase. The diagram below illustrates the theory above. Previous work within industry with enzymes and substrate formed the bases of the prediction above. [] The substrate concentration against the rate of the reaction can be illustrated by the Michaelis-Menten plot.

Vmax is the maximum rate at which the enzyme can catalyse a reaction. Km is the Michaelis constant which is the concentration of substrate that gives half the Vmax. However the Lineweaver-Burk plot gives a more concise value of Km:

The graph above illustrate that as the temperature is increased, the reaction rate of the enzyme also increases however it shows that it reaches a optimum temperature where the reaction proceeds at its maximum. Above this temperature the reaction decreases. This is due to the bonds within the enzyme breaking changing the 3d shape of the enzyme and therefore denaturing. Taking this theory in to account with the research being carried out it would be expected that at the optimum temperature of around 37ºc the acid phosphatase will start to denature and the rate of reaction above this temperature will decrease. Many enzymes are sensitive to ph and they all have a specific range of activity. All enzymes have an optimum ph and effects the enzymes 3 dimensional shape by breaking its weak non covalent bonds such as hydrogen bonds and ionic bonds causing the enzyme to denature. Acid phosphatase optimum ph will be below 7 it would work best within the range of 4.0-6.0. Enzyme inhibitors are substances which interfere with the catalytic action of the enzyme. They slow down or completely stop the reaction. These include reversible and non reversible. Reversible inhibitors are further more be classified as competitive and non competitive. A competitive inhibitor closely resembles the substrate. The inhibitor competes form the same active site as the substrate. The inhibitor...
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