An experiment to investigate the effect of temperature on the action of the enzyme lipase.

Authors Avatar

Ambareen Naqvi 10K

An experiment to investigate the Effect of Temperature on the Action of the Enzyme Lipase

Introduction

In this experiment I will be investigating how temperature affects the rate of reaction of enzymes (lipase) on substrates (fats). This investigation will allow me to gain a greater knowledge of enzymes and how they work. In this experiment I will only be investigating one factor that affects the action of enzymes. The other factors that might affect the action are the concentration of the enzyme and the concentration of the substrate. According to how concentrated the enzyme or substrate is, it will affect the rate of reaction as a higher concentration of enzymes may make the rate of reaction quicker. (Although we have to take into account the ratio between enzymes and the substrate, as having a too high concentration of the substrate may not affect the rate of reaction). Also if there is a lower concentration of substrate, then the rate of reaction may speed up. To understand how the temperature might affect the rate of reaction, we have to see how enzymes work, especially lipase. Here is an equation that gives the general outline to it.

FAT………………………          FATTY ACIDS + GLYCEROL

Enzymes have an active site in which they break down the substrate. I will talk about this in my conclusion and my evaluation.

        The method I am going to use will help gather results from different temperatures to which the enzymes are exposed to and will enable me to draw a graph. From this I can gather more data on the effects of temperature on enzymes. I will give a detailed method further on in my planning. I predict that the temperature for optimum enzyme activity will occur 40ºC-45ºC. It is known that every enzyme has an optimum temperature and breaching this means denaturing the enzyme. When the temperature gets higher, there is enough energy to break some molecular bonds in the enzyme. This alters the active site so the enzyme can no longer accept the substrate and so cannot break it down. At any temperature above this the enzyme will not be able to break down the milk and so the reaction will not take place. At temperatures lower than this, it will only take longer as the enzyme is still working, but it does not have enough energy to break the substrate down. There are theories behind my predictions. The Kinetic Theory states that if there is double the heat, there will be double the energy and so the reaction will go double as quickly. Also the Collision Theory will come into play as twice as much heat means twice as much collisions and so the rate of reaction will be doubled.

        I have explained how lipase digests fat, and I will explain how the phenolphthalein works. This turns purple in an alkaline solution, but colourless in an acidic solution. This will help me time the rate of reaction because I will see how long it takes for the solution to turn colourless (a milky colour in this case) from purple. This will tell me the rate as the reaction will produce fatty acids that will neutralise the alkaline solution.

        I did do an experiment at 25ºC, telling me for how long to keep timing. From the results I obtained (they are in my results section), I concluded that I would keep timing until 360 seconds as that was sufficient time for the lipase to break down the fats in the milk.

Method

The water bath was set up as the diagram below.

It was set up as 40ºC using warm water from the tap. The other temperatures I used were 50ºC, 60ºC, 70ºC and 30ºC. For 50 and 60, I used an electronic water bath and for 30 and 70 I used a water bath that I set up. Three test tubes were labelled, three with the numbers 1,2,3 and one labelled C for control. In each test tube, 3cm3 of milk into each test tube. Another 3cm3 of sodium carbonate was added. This made the solution alkaline so we could see the rate of the reaction. Eight drops of phenolphthalein was added to the milk. This was the indicator from which we were able to determine the change in pH. The colour went pink. All the test tubes were placed into the water bath and were brought to the right temperature. When they had reached the right temperature, 1cm3 of lipase was added to three test tubes, not the control. The 1cm3 of lipase was prepared before. The stopwatch was started at the same time the lipase was added to the solution. When the enzyme was added the solutions were stirred for five seconds alternatively. The solutions were watched to see when they turned a milky colour (colourless) and the time recorded.

Join now!

Results

Here the tables of my results, along with another two groups. Here are my results first.

Here the second groups.

Here is the third group’s set of results.

The graphs I made from results are on a different piece of paper. Along with a time graph I have also done a rate of reaction graph. The rate of reaction graph will be more accurate as I am measuring the arte of reaction. I have found some anomalous results in my results table, which I will explain now. I have circled them in red. The reason for the anomalous ...

This is a preview of the whole essay