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Investigating the digestion of gelatine with the enzyme trypin.

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Investigating the digestion of gelatine with the enzyme trypin. Aim: My aim is to investigate the effects of changing the temperature on the rate of reaction of a protease enzyme called trypsin. I want to find out at what temperature it will work fastest to digest gelatine. A photographic company wants to recycle the unsuitable plastic photographic film. They will need to remove the silver compound, which is attached to the film by the protein gelatine. They decide to use trypsin to digest the gelatine, but they want to find the best conditions for the enzyme to work to save money. Introduction: Exposed photographic film contains black grains of a silver compound. These grains are stuck onto the plastic photographic film by an insoluble protein called gelatine. This means that the film is not transparent when the silver compound is attached to it. Enzymes are specialised organic substances, composed of polymers of amino acids, that act as catalysts to regulate the speed of the many chemical reactions involved in the metabolism of living organisms. The name enzyme was suggested in 1867 by the German physiologist Wilhelm K�hne (1837-1900); it is derived from the Greek phrase en zyme, meaning "in leaven". Identified enzymes now number more than 700. Structure and Function of an Enzyme Enzymes are large proteins that speed up chemical reactions. In their globular structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, or the location on the enzyme where the substrate binds and the reaction takes place. Enzyme and substrate fail to bind if their shapes do not match exactly. This ensures that the enzyme does not participate in the wrong reaction. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate. Enzymes are classified into several broad categories, such as hydrolytic, oxidising, and reducing, depending on the type of reaction they control. ...read more.


The concentration of substrate can alter the rate of reaction because if it is higher then there will be more frequent collisions with enzymes and therefore a higher rate of reaction. If the concentration of the substrate is lower then collisions of enzymes and substrates will be less frequent and the rate of reaction will be slower. The concentration of enzymes affects the rate of reaction in a similar way because if there is a lower concentration of enzymes then there will be less frequent collisions and the rate of reaction will be slower. If there is a higher concentration of enzymes then there will be more frequent collisions and therefore a faster rate of reaction. Effect of inhibitors: Enzyme inhibitors are substances, which alter the catalytic action of the enzyme and consequently slow down, or in some cases, stop catalysis. There are three common types of enzyme inhibition - competitive, non-competitive and substrate inhibition. Most theories concerning inhibition mechanisms are based on the existence of the enzyme-substrate complex ES. The existence of temporary ES structures has been verified in the laboratory. Competitive inhibition occurs when the substrate and a substance resembling the substrate are both added to the enzyme. A theory called the "lock-key theory" of enzyme catalysts can be used to explain why inhibition occurs. The lock and key theory utilises the concept of an "active site." The concept holds that one particular portion of the enzyme surface has a strong affinity for the substrate. The substrate is held in such a way that its conversion to the reaction products is more favourable. If we consider the enzyme as the lock and the substrate the key (Figure 9) - the key is inserted in the lock, is turned, and the door is opened and the reaction proceeds. However, when an inhibitor which resembles the substrate is present, it will compete with the substrate for the position in the enzyme lock. ...read more.


Another inaccuracy was that we had to take the splint out of the test tube every few seconds to check how much of the silver compound (if any) had been dissolved. Even the same person may have done this at different intervals and may cause the results to be inaccurate. This could've been prevented if there was a set time at which we would check the film e.g. every 30seconds. The pieces of photographic film being used weren't all exactly the same size. They were only cut roughly the same size and were not measured. This would have caused inaccuracy because the concentration of the substrate was to be kept exactly the same for each experiment in order for it to be fair. If the pieces of photographic film were not exactly the same size then this means that the concentration was slightly altered which may cause inaccurate results. This could've been improved if the pieces of photographic film were accurately measured exactly the same size each. The experiments were conducted on three different days. This is inaccurate because the efficiency of the enzymes would decrease with time and may cause the trypsin not to catalyse the breakdown of gelatine as efficiently the second time as it did the first time. This could've been improved if a new solution of trypsin was used each lesson. Our experiment could have also been more accurate and time efficient if we had organised things before hand and allocated each person in the group with one or two things to do i.e. like the construction line in factories. This would be more precise as the same person is doing the same thing each time and it prevents human error because different people may do things slightly differently. It would've also been a lot less time consuming and we may have had time to do more experiments e.g. 10 oc or 70 oc, it would give us clearer results and a more accurate conclusion. 8 May, 2007 Sara Saidpour Ms Ayub 11LO Biology Coursework 1 ...read more.

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