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The Action of Enzymes

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The Action of Enzymes PLAN Background information (theory) In our body, large molecules of food that we eat need to be broken down into smaller ones so that they can be absorbed into the bloodstream (otherwise they would be too big to do so). Our bodies alone can do this but it takes such a long time that human life wouldn't exist anymore because we wouldn't get the required nutrients quick enough to survive. Therefore, our bodies use enzymes to speed up these chemical reactions that take place in our bodies. They do this by lowering the activation energy of the reaction so that it can take place at a lower temperature. Enzymes are biological catalysts, which means that they do not get used up during the reaction because they are not chemically changed during a reaction and can be used over an over again by our bodies. This all means that enzymes are needed in only small quantities as they are efficient and work quickly. There are two types of enzymes. Both are made inside cells but one of them leaves the cell and it works outside it. These enzymes are called extracellular enzymes (also called exoenzymes). These enzymes usually break down large food molecules which cannot enter the cell into smaller ones so that they can enter the cell. The other type of enzyme are called intracellular enzymes (also called endoenzymes). These enzymes speed up chemical reactions inside our cells and also control them. During the reaction, the substance in which an enzyme acts on is called the substrate. The new substances made from each reaction are called the products. So when a reaction is happening, the different types of enzymes and substrates are moving about in different directions. So when a substrate molecule bumps into the right enzyme, it fits into a depression in the enzyme. This depression is called the active site. ...read more.


This is what the end point for the reaction will be. Firstly, I will draw a cross on a piece of paper. I will place the beaker with the test-tubes inside it on top of the cross. As the reaction starts to go clear after a while, I will stop the stopwatch when I can see through the reaction and onto the cross. I will do the same for each temperature. Controlled variable - these are the things which I will need to keep the same during the reactions. Therefore, I will use 4g of milk and 0.5g of trypsin in 100cm3 of water for each reaction. This is to keep it a fair test. If I use more trypsin, then there will be more enzymes to break down the milk, so the rate of reaction will be quicker and the solution will turn clear quicker. If I use more milk, it will take the trypsin longer to break down the milk, as there will be more molecules of milk to break down, so the rate of reaction will decrease and the reaction will take longer to turn clear. I will also need to keep the pH of each reaction the same. This is because the pH can affect enzyme activity. If the pH is a lot lower or a lot higher than the optimum temperature for the trypsin, it may denature and the reaction will happen slower and the rate of reaction will decrease. Method 1. I will put 100cm3 of water into a beaker and will make sure that the temperature of the water is at normal room temperature. 2. On a piece of paper, I will draw a cross on it and place the beaker on top of the cross. 3. In a test-tube, I will add 4g of milk. I will then add 0.5g of trypsin and as soon as the trypsin hits the milk, I will start the stopwatch and place the test-tube inside the beaker. ...read more.


However, I thought that the procedure was suitable for the investigation. For example, I was using the right enzyme for the right substrate, i.e. trypsin on casein. I thought that drawing a cross to see when the reaction was over was a good idea because it gave me the chance to record a result without waiting too long for it. However, this could have changed some of the results, because it depended on when I thought the reaction had ended, and not when it had actually ended. However, I only found one anomaly from my results for 25oC, but it did not affect the line of best fit at all. The equipment could have increased or decreased the amount of enzyme and substrate I put in the reaction, but this would have been such a small difference, that I doubt it could have affected the results greatly. For example, if I measured and put in a little bit more of trypsin than was needed, there would have been more enzymes which would have broken down more substrate which could have decreased the reaction time, thus increasing the rate of reaction. Also, I had one anomalous result. I thought that it was anomalous because a long way off the line of best fit. This could have been caused by a human error during the reaction. This may have been because I measured the temperature, and then waited a long time before starting the reaction, so the reaction could have cooled down and the reaction time could have been changed. One way I could have improved the experiment would have been to found a better way of finding when the reaction had ended. The way I did it was to draw a cross under the beaker, and when I could see the cross, measure the time and record it. However, there were problems with this which I have mentioned above. A way I could have improved this method would have been to let the reaction finish completely before recording the result. ?? ?? ?? ?? Biology coursework ...read more.

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