Active Site On The Enzyme Molecule example essay topic

Information on enzymes & rennin Enzymes are biological catalysts that speed up reactions without being affected so that they can be used to speed up another reaction. Enzymes are soluble globular proteins. Enzymes reduce the energy needed to make a reaction happen. This energy is known as the "activation energy". We need enzymes to stay alive, without them, the reactions in our body would take place far too slowly. Also, we need to be able to control how fast certain reactions take place, if we didn't have enzymes, all our bodies reactions would take place at different speeds.

Certain poisons such as cyanide block the active site, and so stop the enzyme from working. To understand the investigation better, here is some background information on rennin. Rennin is produced inside young mammals as a way of converting caseinogen into casein. It needs to do this to absorb the precious proteins in the milk that it feeds on. Caseinogen is soluble, and is very hard to separate from water and as a result, it would not stay in the digestive system long enough to be absorbed and the mammal would die. Rennin converts the caseinogen into casein, (which is insoluble) so that it remains in the digestive system for much longer.

This enables it to be broken down and absorbed into the mammals blood stream. Hypotheses on the effect of temperature As the temperature increases the rate of reaction increases as well. At a certain point the enzyme starts to be denatured which dramatically decreases the rate of reaction. The reaction we have investigated is: Caseinogen Casein More commonly known as the "curdling of milk". My graph shows that as the temperature increases, the rate of reaction increases as well. This is because as the temperature increases, each molecule of rennin and caseinogen has more energy, and as a result, the chances of the molecules colliding are increased.

Also, as the molecules have more energy when they do collide, they have enough energy to react... An increase in temperature increases the likelihood of successful collisions. As the temperature increases the atoms that make up the enzyme molecules vibrate harder and with more intensity. This puts a lot of strain on the chemical bonds between the atoms. At the "optimum temperature" now identified as 70 oC (see graph) (also see Evaluation) the bonds between the atoms break, and the active site becomes deformed, stopping the enzyme from working.

When this happens we say the enzyme as been "denatured.".. Rennin starts to be denatured at temperatures above 70 oC. This is a hypothetical diagram of an enzyme molecule (rennin) and a substrate molecule (caseinogen). I am using the "lock and key hypothesis". If the substrate molecule (caseinogen) bumps into the active site on the enzyme molecule (rennin) then they will fit together. But unless there is enough energy, they won't react and the substrate molecule will not react and will leave unchanged.

If there is enough energy to make a reaction take place, such as when the temperature is increased, then the substrate molecule will react to form the product, which, being a different shape is pushed out of the active site by the enzyme molecule. The new molecule (s) is / are called products. This is just one hypothesis of how enzymes work. For instance a different hypothesis, for example the induced fit hypothesis, suggests that enzymes are not rigid structures and so mould themselves around the substrate molecule to make a perfect fit. This theory would account for how some enzymes are able to catalyse more than one reaction. This theory is also known as the "glove fit" hypothesis.

The results that I obtained are roughly what I expected but the reasons I got the results are different. For instance, I obtained an average rate of reaction of 0.3 for my experiment at 20 oC. This can be explained by the theory above: The enzyme and substrate molecules are moving around inside the solution. They do not have a lot of energy and are not moving very fast. If a rennin and a caseinogen molecule collide, and if the caseinogen lands in the rennin molecule's active site, then there is a chance that the reaction may occur.

Whether it does or not is determined by the amount of energy they have. If there is enough energy the caseinogen molecule will change into a casein molecule and will be pushed out of the active site, leaving the rennin molecule free to catalyse another reaction. At 70 oC the enzyme and substrate molecules are moving around inside the solution much faster than they were at 20 oC. This is because they have more energy, measured by taking their temperature. If a rennin and caseinogen molecule collide, and the caseinogen molecule lands in the active site of the rennin molecule, then it is almost certain that a reaction will take place.

This is because there is a lot more energy and therefore the "activation level" is easily obtained. Also, because the temperature has been increased, and the molecules are moving around faster, there is more probability that they will collide. At 80 oC the chemical bonds that hold the atoms in the enzyme together snap, because the atoms around it are vibrating so hard. This causes the enzyme to lose its shape (in particular the active site) and it becomes denatured.

Now, even though there is more energy, and more chance of a collision (owing to the fact that the molecules are moving faster) the reaction does not take place. This is because the active site is a different shape to the caseinogen molecule and the latter can no longer fit in it. This is the equivalent of using amylase (another enzyme) to do this experiment; the active site is the wrong shape for the substrate molecule. Evaluation of Prediction My prediction was incorrect; it stated that the optimum temperature of rennin would be around 40 oC.

As my graph and table show, at 70 oC the rate of reaction is 4.1, more than twice as fast as at 40 oC (1.8). The reason for this is a complicated one. On further examination of the rennin, it appears that the rennin we used for our investigation came from fungi rather than from calves. There is an ethical dilemma over whether it is morally right to kill a baby animal for the rennin in its stomach. Fungi use rennin for the same purpose as mammals, they secrete the rennin onto the ground to stop the caseinogen dissolving in the water. Then they secrete other enzymes and acids to break down proteins in the soil into amino acids which they then absorb.

Obviously, the rennin used in fungi is not the same as in mammals, it is more thermostable (able to withstand high temperature) than the rennin produced by mammals. Fungi have evolved this type of rennin probably because of their encounters with heat. In a calf, for example, the temperature never rises above 40 oC, if it did, the calf would die. There is no reason for the calf to have such a thermostable enzyme, it would be more useful for the calf to have an enzyme that could withstand very acidic conditions, like those you get inside their stomachs. N.B. The acids that the fungi secrete are very mild in comparison with the acids found in the stomach (s) of mammals, therefore the rennin enzyme in fungi would favour only weakly acidic conditions. My prediction also stated that the rate of reaction would double every time the temperature increased by 10 oC. This was also incorrect, only at one point did this match the results I obtained.

If you had carried out a reaction at approximately 25 oC and again at 35 oC then you would have doubled the rate of reaction... From 20 oC to 30 oC the rate of reaction more than trebled. (0.3 to 1.0. ). From 60 oC to 70 oC the rate of reaction increased by just less than 50%. (4.1 to 6.1.) Anomalies After producing a dispersion table (a table that shows up any anomalies) I could only find two results that could have been classed as anomalies.

They are the result I gained on the second experiment of the investigation at 20 oC and the result that I gained on the first experiment of the investigation at 30 oC: 275 seconds and 91 seconds respectively. I have not classed them as an anomalous result, nor have I left them out when calculating the mean times. However these are results which are less than 90% of the average (outliers) and I did not expect any of the results to be any further from the mean. I decided to leave them in because they are not after all drastically far out, and, having only taken three readings, I cannot be certain that they are not the expected values and that the other two readings are anomalies.

I have indicated which results they are in the table by underlining them. I have treated these results no differently from any other result. There is one other result which fell into this category, and again I didn't count it as an anomaly. It is the result for the second experiment at 70 oC (14 seconds).

I didn't recognise this as an anomaly because it could easily be a product of a rounding error as it is only 2 seconds off the mean. Explanation of results Any box that has a dash in it means that no result was recorded for that experiment, this is because it took more than 10 minutes to discern a reaction taking place. I took this to mean that it would not happen and that the rennin had been denatured (although the milk would eventually curdle on its own). Each result is recorded to a specific level of accuracy, this makes it easier to read the results off the table and also ensures that no rounding errors take place. The rate of reaction was multiplied by 100 to make it easier to understand and to plot on to a graph. If I had not multiplied it by 100 the results would have been ridiculously small.

For instance, 0.0033 is much harder to comprehend than 0.3. The control was done in exactly the same way as the other experiments (I tested the control at 70 oC) except it was done using rennin that had been boiled at 100 oC beforehand and therefore had been denatured. The fact that this experiment failed to give any signs of a reaction proves that it is the rennin that catalyses the reaction and not any other factor. The effects of this are even more conclusive if you consider that before, when I had tested the normal rennin at 70 oC it started to curdle the milk in approximately 16 seconds, yet it had not made a discernable reaction after 600 seconds (10 minutes) with the boiled rennin.