To Investigate the effect of changing temperature on the action of the enzyme catalyse, by measuring the volume of gas produced in 20 seconds

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Coursework – Enzymes

Aim: To Investigate the effect of changing temperature on the action of the enzyme catalyse, by measuring the volume of gas produced in 20 seconds

Method

Catalyse is an enzyme found in all living cells. It makes Hydrogen Peroxide decompose into water and oxygen. We are going to measure the amount of oxygen released from the hydrogen peroxide, during a 20 second period, to try and find out how quickly the reaction is happening. We will conduct the experiment under different temperatures, measuring the volume of gas produced each time using a gas syringe.  

The Chemical Reaction

Hydrogen Peroxide                               water + oxygen

Prediction

Volume of gas produced:

In other words, when the temperature is increased, the rate of enzyme activity will also increase: for every 10°c rise in temperature, I predict that the rate of enzyme activity will roughly double. For example, increasing the temperature the experiment was conducted under from 20°c to 30°c, I would expect the rate of enzyme activity to be roughly double what it was at 20°c.

I also predict that as I raise the temperature to 30, 35 and 40°c, this is where I will see the greatest reaction. I predict this because enzymes are designed to work best at the internal body temperatures of the animals they belong to. For a mammal, this tends to be somewhere around 37°c.

        I also predict that if the temperature is increased to higher than 40-45°c, enzyme activity will begin to decrease and eventually cease completely. I know this because enzymes are proteins, which denature under high temperatures. An enzyme must remain a specific shape if it is to successfully break down molecules.

ANALYSING AND CONCLUDING

Graph and Line of Best Fit

I have drawn a graph showing the results that I have collected. The correlation of the points made it possible to draw a line of best fit onto my graph. By looking at the graph it is possible to find the optimum temperature for enzyme activity, by looking at where the line peaks.

What I Have Found Out

By looking at the graph you can see that the line of best fit shows a clear relationship between temperature and the rate of enzyme activity. At first, the rate of enzyme activity is increased, the higher the temperature. The rate of enzyme activity peaks somewhere between 37°c and 40°c although the lack of points makes this hard to be sure of, as we cannot really be certain about what is happening around that area of the graph, and the only way to prove it would be to conducts further tests using temperatures close to where the rate of enzyme activity appears to peak. After it peaks, the line of best fit shows the rate of activity starting to decrease, as the temperature continues to be increased.

        In summary, I have found out that the breakdown of the liver accelerates as the temperature is increased, until the optimum temperature is reached, after which it starts to slow down. Temperature influences the rate of enzyme activity.

N.B. 

A 10°c rise in temperature, roughly doubles the rate of most chemical reactions. This can clearly be seen on the graph:

  • A line draw vertically upwards from 20°c on the x axis to the line of best fit, then drawn horizontally from that point towards the y axis lands on approx. 6 ml of gas.
  • A line draw vertically upwards from 30°c on the x axis to the line of best fit, then drawn horizontally from that point towards the y axis lands on approx. 12 ml of gas.

This proves that doubling the temperature from 15°c to 30°c roughly doubles the volume of gas collected: from 5 ml to 10ml.

In other words: a rise in temperature of 10°c roughly doubles the rate of enzyme activity.

How Close Is This To My Prediction?

I predicted that the higher the temperature, the faster the rate of enzyme activity. I predicted this because I already know that heat speeds up most chemical reactions. This is clearly the case with my actual results.

My prediction also states that if the temperature is increased by 10°c, the rate of enzyme activity will roughly double. This is shown to be correct by my results table and my line of best fit. For example my graph shows that doubling the temperature from 15°c to 30°c, roughly doubles the volume of gas collected (rate of enzyme activity).

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I also predicted that the rate of activity would decrease when the temperature got beyond a certain point, which is shown on the sample graph I drew for my prediction. This is exactly what happened during the actual experiment.

I also correctly predicted approximately where the rate of enzyme activity would peak, and where it would begin to decrease.

The sketched line of best it that I drew for my prediction accurately resembles the actual line of best fit on the graph I drew displaying the results of the investigation. This line shows the increase in enzyme activity as temperature ...

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