Rate of reaction of Trypsin.

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Suraj P. Nakum 10I        GCSE Science Coursework        Page /

Rate of Reaction of Trypsin

- An Investigation -

Planning

Aim:

To investigate how the concentration of trypsin affects the rate of reaction.

Background Knowledge:

Enzymes exist in all living things. They are composed of polymers of amino acids and are produced in living cells. Each cell contains several hundred enzymes, which catalyse a vast number of chemical reactions. Enzymes are known as biological catalysts as they dramatically increase the rate at which reactions occur within living organisms, without being ‘used up’ or effecting the reaction in any other way.

Trypsin is an enzyme which digests proteins, and in this investigation I will use it at different concentrations to see how it affects the rate of reaction.

Reaction:

This is the reaction that we will be investigating:

Changing milk protein (- white, large, and insoluble molecules)

                                        Amino acids (- colourless, small, and soluble molecules)

Hypothesis:

Reaction rates are explained perfectly by the Collision Theory. It says that the rate of a reaction depends on how often and how hard the reacting particles collide with each other. The basic idea is that particles have to collide in order to react, and they have to collide hard enough as well. If a solution is more concentrated it means there are more particles of reactant knocking about between the water molecules which makes collisions between the important particles more likely. Similarly, when the temperature is increased, the particles move quicker; and if they’re moving quicker, there’s going to be more collisions. Therefore, my prediction is that the higher the concentration of trypsin, the faster the rate of reaction will be. The more trypsin molecules there are in a lesser volume of milk, the higher the probability that the trypsin molecules will collide with a milk protein. In my opinion, it all depends on how great a probability there is for the collision theory to take place in the solution.

Apparatus:

  • Beaker
  • Measuring cylinders
  • Pipettes
  • Test tubes
  • Trypsin enzyme @ different concentrations: 0.2%, 0.4%, 0.6%, 0.8%, 1.0%
  • Powdered Milk (4% concentration)
  • Hydrochloric acid
  • Stopwatch
  • Thermometer
  • Safety goggles

Diagram:

Preliminary work:

For our preliminary work we investigated the speed of the reaction between milk proteins and trypsin at different temperatures. We finished this investigation by saying that ‘as the temperature increased the reaction took place faster’. This was because at higher temperatures, the heat was transferring more kinetic energy to the enzymes which caused them to collide with the milk proteins with more force than it did at lower temperatures. This extra force that was being used by the enzymes allowed them to digest the proteins at a faster rate. However, at a certain temperature, the rate of reaction eventually started to slow down.  This eventual deceleration in the time being taken to digest the proteins was due to the fact that at a certain high temperature, the enzymes eventually denaturise. So much kinetic energy was being transferred to the enzymes by the intense heat, that the force the enzymes collided with the proteins was so great it damaged the actual active site within the enzymes. With the shape of the active site being changed, the enzyme was no longer able to digest that particular substrate (milk protein), and therefore the number of ‘working’ enzymes decreased.

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As a result, the speed of the reaction slowed down, since there were fewer enzymes to do the job.

Consequently, we concluded this preliminary investigation by saying that:

“As the temperature increased, the rate of reaction increased accordingly, nevertheless, at a certain temperature the enzymes denatured which slowed down the rate of reaction significantly.”

Method:

1.         Firstly, we put on our goggles and place a measuring cylinder on the table. We then measure out 5ml of Hydrochloric acid into the measuring cylinder, and then pour it into a test tube. In the same measuring ...

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