After the first run, the second and third followed consecutively in exactly the same way remembering to keep the amount of hydrogen peroxide the same and increasing the amount of yeast suspension by 5cm3 each time. By about the third attempt the investigator should notice a slight trend that the volume of gas collected was more or less the same as formerly and after undertaking the fourth and fifth runs, the investigator should realise that this is crucial.
Enzymes are defined as biological catalyst which speeds up the rate of a chemical reaction. An enzyme speeds up a reaction but the molecule itself remains unchanged. Enzymes are quite specific, as they have a cleft or crevice on the surface called an active site. Which is part of the molecule to which the substrate can bind perfectly and is held together by bonds, this is usually referred to as ‘The Induced Fit Hypothesis’. Each enzyme normally acts on one type of substrate because the shape of the active site may not allow any other shape molecules in because of the difference in shape. When the enzyme molecule catalyses the substrate, a product(s) is formed. After the completion of a reaction, the product(s) leave the active site and thus the enzyme is unaffected by this and so is now free to receive another substrate molecule.
In this case the substrate in question is the hydrogen peroxide and the enzyme is the yeast suspension and the product(s) are oxygen gas. In method 1 the volume of yeast was increased each time but the volume of hydrogen peroxide was kept the same. So the investigator should have noticed when taking down the results, that the amount of oxygen being collected was more or less the same after each run but the time taken for each one was quicker than the last run. The reasons for the same amount of product being produced after each run being the same to do with enzyme concentration (yeast). During each run the enzyme was being increased and the substrate was being kept constant. This means that there were a lot more enzymes working with limited substrate concentration and so the enzymes will have produced the products more quickly if there was more of it. For example if 10 miners (enzyme) were mining a small coal mine (enzyme) it would probably take some time for the coal (product) to be retrieved. But if there were 15 miners then it would take them a shorter period of time to mine and 20 miners would take them even a shorter time and so on. But the product, which is the coal, will always remain the same because that’s all the coal the mine has to offer.
Method 2: - The effect of concentration of enzyme substrate on the rate of _ an enzyme catalysed reaction.
In method 2, the amount of substrate (hydrogen peroxide) was increased after each run and the amount of enzyme (yeast) was kept constant during each run. The results concluded were that the amount of product collected was higher in each run than previously.
The reason behind this is that the volume of the hydrogen peroxide (substrate) was being increased each time yet the yeast (enzyme) was kept constant, so the enzyme was producing more products because there was more substrate available to bind to. Once one enzyme molecule binds to a substrate molecule and produces the products it is free for it to find another substrate molecule and in this case the enzyme is kept the same but the substrate was increased which results in more product being produced but at a slower time. In other words an enzyme molecule and a substrate molecule undergo the induced fit hypothesis to result in a product(s) being produced. The enzyme then remains unchanged from the reaction and the active site is not binding to anything so the enzyme is now free to look for another substrate molecule in order to repeat the reaction. The enzyme will keep doing this until the entire substrate molecule is used up. So by increasing the amount of substrate and keeping the enzyme unchanged, the enzyme has to do more work because there is more substrate and because there is more substrate there will be more products.
Another way to explain it is that if 10 miners (enzyme) were mining a coal mine (substrate), they would eventually get the coal (product). But if the same amount of miners had to mine a bigger coal mine then obviously it would take them longer in terms of time, but the coal would be greater in number because of the how big the coal mine was.
Evaluation
The experiment being researched was not extremely accurate because of random errors taking place, but the results were fair enough to draw conclusions from. The systematic errors which took place and affected the experiment and thus affected the results are as follows.
The first error that was concluded was that during the set up of the apparatus, the rubber bung which was inserted into the yeast filled test tube should have been air tight so that none of the gas could escape from minuscule spaces which the bung should have covered up. But in some cases the test tube was bigger than the rubber bung so gas from the reaction would almost definitely escape which would make the results incorrect. The second noted error would be that when inserting the needle on to the bung, the needle may move causing punctures in the bung where gas can escape, furthermore when taking the syringe out of the bung the same problem may occur by the investigator moving the needle vigorously causing in holes being present from which the gas can escape.
Another error would be that the clip which was connected to the rubber tubil may not have been very tight in connection with the rubber tubil, consequentially gas bubbles would appear in the inverted barrel before the reaction took place which would muddle up the results, also the investigator should remember to release the clip after each run so that no gas would be left behind with the inverted barrel. In addition the beaker of water in which the inverted barrel was placed, may have been minutely smaller or the same size as the inverted barrel so thus the barrel would not fill up which resulted in gas being in the barrel already once the reaction was started.
Another detrimental error was that when taking up the hydrogen peroxide using the syringe, sometimes bubbles would appear which made the measurement of how much hydrogen peroxide was used in each run, quite difficult. The final error noted was that in the yeast suspension there was quite a lot of froth built up. So when measuring how much yeast was needed, the volume recorded was not accurate because if u recorded 10cm3 of yeast it may have 12cm3 of yeast.
