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Effect of enzyme concentration on rate of reaction

Extracts from this document...

Introduction

Title : Effect of enzyme concentration on rate of reaction Objective : To investigate the effect of enzyme concentration on rate of reaction Introduction : Enzyme A catalyst is a substance which speeds up the rate of reaction without changing the product and is left unchanged at the end of the reaction1. An enzyme is a biological catalyst that catalyses metabolic reactions in your body such as digestion and respiration. At any time, many reactions are occurring simultaneously in our bodies. There are two types of reaction that is the anabolic reaction and the catabolic reaction. An anabolic reaction is a reaction that results in the formation of a substance from two or more substrate molecules while a catabolic reaction is a reaction that involves the breakdown of a substance into two or more product molecules. A combination of biochemical reactions like these are known as metabolism.. Enzyme action can be intracellular that is within cells or extracellular that is outside cells. Extracellular enzymes such as digestive enzymes are effective in the digestive tract while intracellular enzymes are found in the cytoplasm, nucleus, mitochondria and chloroplasts in cells.2 Enzymes are complex proteins which have are made of several polypeptide chains joined together. Enzymes have a tertiary or quaternary structure which is held together by bonds such as hydrogen bonds, disulphide bridges, ionic bonds and hydrophobic and hydrophilic interactions to form a 3D shape which is very precise. The polypeptide chains in the enzyme molecule fold to form a cleft which is known as the active site. As a result of the precise 3D structure of the enzyme, the active site has a distinctive shape. Enzymes are very specific and usually only catalyse one reaction. This is because only one substrate will fit into the active site. The shape of the active site is determined by the 3D structure of the enzyme as aforementioned. ...read more.

Middle

8. Step 1-7 is repeated thrice by using two, three and four spatulas of blended potato instead. 9. The times and volume of oxygen gas collected is tabulated. (Table 1) 10. A graph of volume of gas collected against time is plotted. (Graph 1) 11. The initial rate of reaction is calculated from the gradient of the curve at point (0,0) and tabulated. (Table 2) 12. Another graph of initial rate of reaction against enzyme concentration is plotted. (Graph 2) Results: Time (s) Volume of oxygen gas collected for each number of spatulas of blended potato (cm3) 1 spatula 2 spatulas 3 spatulas 4 spatulas 0 0.0 0.0 0.0 0.0 10 2.0 4.4 5.9 7.0 20 4.0 7.6 10.4 11.0 30 5.2 10.0 13.4 15.0 40 6.2 12.2 16.0 18.4 50 7.6 14.2 18.0 21.0 60 0.0 0.0 0.0 0.0 Table 1: Volume of oxygen gas collected for each number of spatulas of blended potato Graph 1: Graph of volume of oxygen gas collected against time for each number of spatulas of blended potato Calculations of initial rate of reaction For 1 spatula of blended potato, Initial rate of reaction cm3s-1 cm3s-1 For 2 spatulas of blended potato, Initial rate of reaction cm3s-1 cm3s-1 For 3 spatulas of blended potato, Initial rate of reaction cm3s-1 cm3s-1 For 4 spatulas of blended potato, Initial rate of reaction cm3s-1 cm3s-1 Enzyme concentration (spatula) Initial rate of reaction (cm3s-1) 1 0.2 2 0.417 3 0.633 4 0.75 Table 2: Initial rate of reaction for different enzyme concentrations Graph 2: Initial rate of reaction against enzyme concentrations Discussion: Graph 1 is a graph of volume of oxygen gas collected for each number of spatulas against time where there are four curves with each curves representing the enzyme concentration for one, two, three and four spatulas respectively. From the data tabulated in Table 1 and the curve plotted in Graph 1, it can be observed that the general trend is that an increase in enzyme concentration is followed by an increase in the volume of oxygen. ...read more.

Conclusion

The diameter of the boiling reduces the risk of having blended potato stuck on its sides as the diameter is wide enough for a spatula to enter and push the blended potato down. Another significant error was that the bung could not have been closed immediately after the hydrogen peroxide is poured into the test tube containing the blended potato. As a result, a large amount of oxygen released by the decomposition of hydrogen peroxide escaped into the surroundings and was failed to be collected during the time taken to fix the bung tightly to the test tube. For this reason, the arrangement of the apparatus could be changed to prevent the oxygen from escaping and thus obtain a more accurate reading of the volume of oxygen collected for each different enzyme concentration. A conical flask should replace the test tube. A bung with two holes of which, one is attached to the delivery tube to the graduated tube. A syringe containing hydrogen peroxide is then inserted into the other hole of the bung and the plunger is pressed to add the hydrogen peroxide to the blended potato in the conical flask. This would lead to more accurate results as only a small amount of air would have been lost and thus has smaller effect on the results obtained. Safety Precautions: A lab coat should be worn at all times in the lab to prevent clothes from any stains if any spills occur. Closed shoes should be worn in the lab to provide adequate protection in case of any mishaps. Caution must be applied when handling hydrogen peroxide as it is corrosive due to its high oxidising power. Any spillage on the skin should be washed under running water immediately. Glass wares used in experiment should be handled with care to prevent cracking or breakage as small fragments of glass wares that have been broken are sharp and may cut and cause bleeding. Conclusion: It can be concluded that as the enzyme concentration increases, the rate of reaction of a biochemical process increases. The hypothesis is accepted. ...read more.

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Response to the question

Response to the question is done to a high scientific level. Introduction and scientific conclusions and analysis throughout the experiment are all to a significantly good level. However, the candidate could have used a broader basis for their experiment to ...

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Response to the question

Response to the question is done to a high scientific level. Introduction and scientific conclusions and analysis throughout the experiment are all to a significantly good level. However, the candidate could have used a broader basis for their experiment to gain a better mark.

Level of analysis

The scientific explanations behind the experiment and the buffer solution are very in depth and well explained. The scientific basis behind the remainder of the experiment is very well explained but has a very chemistry like slant. To increase their grade the candidate could analyse the percentage errors that might be made by the equipment in the experiment and how to improve this. The candidate could also have investigated other factors which may affect the rate of enzymes to get an overall view of how the enzyme works.

Quality of writing

Punctuation, grammar and spelling are all accurate.


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Reviewed by skatealexia 07/04/2012

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