How the concentration of amylase effects the digestion of the starch.

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How the concentration of amylase effects the digestion of the starch.

Aim: To investigate whether changing the concentration of enzymes makes a difference to the rate of reaction.

Planning:

        

         Enzymes are biological catalysts. They speed up the chemical reactions, which go on inside living things. Enzymes provoke all the process necessary for life. Minerals, vitamins and hormones need enzymes to be present in order to do their work properly.They are very efficient at their job. Enzymes are made inside cells. Once formed, the enzyme may leave the cell and work outside.

 

        Substrate                                                                Product        

Enzyme

      -------------------------------------

 

                                                                                                             

The substance which the enzyme acts on is called the SUBSTRATE .The new substances formed as a result of the reaction are the PRODUC. For convenience enzymes are usually given a name similar to that of the substrate but with the ending ‘ase’.

PRELIMINARY WORK-         Before starting my actual experiment for my investigation, I had prepared some preliminary. In this experiment I tried out, with different concentrations of amylase with starch to see how long it would take for the starch to convert into glucose. In order to determine the end point of the reaction, I used iodine solutions; this was my indicator because I knew that when iodine is added to starch it produces a blue/black color.

 

Apparatus used:

  • Amylase solution
  • Starch solution
  • Iodine solution
  • Spotting tile
  • Stop watch

Method for my preliminary experiment

  1. I collected the listed apparatus and safety equipment.
  2. I cleaned them to get rid of any other chemicals, as this could affect my experiment.
  3. Set up my experiment
  4. Put one drop of iodine into each well on a spotting tile
  5. Added 1cm³ of amylase to 5cm³ of starch solution in a test tube.
  6. I took a drop out of the test-tube and added it to the iodine on the spotting tile, at certain times. (30 sec intervals)

This experiment was not accurate as the time intervals of 30 seconds give a rounded up result. At 30 seconds it could have been 24 or at 1min 30sec it could have been 1min24sec. However this experiment proves that iodine works and how long it takes for it to work, it contributes for me to make a quantitative prediction. It also gives me an insight to how many times to repeat the experiment.  

Prediction:

        I predict that when I do the experiment the rate of reaction will be fastest when the concentration of amylase is 100% and slowest with a concentration of 10%, so ‘as the concentration of amylase increases the time taken for the starch to be broken down decreases’. The rate of reaction is explained by ‘the collision theory’. The collision theory states that, at higher concentration there is higher pressure so molecules are constantly moving about and bumping into each other. When a substrate molecule bumps into a molecule of the right enzyme, it fits into a depression on the surface of the enzyme molecule. This depression is called ‘the active site’. The reaction then takes place and the molecules of products leave the active site, freeing it for another substrate molecule.

The active site of a particular enzyme has a specific shape into which only one kind of substrate will fit. The substrate fits into the active site rather like a key fits into a lock, this is known as the ‘lock and key theory’. This is why enzymes are specific in their action.

        When concentration is increased the number of collisions between the enzyme and substrate molecules also increases forming what is called an ‘enzyme-substrate complex.’(Shown below), therefore resulting in more active sites being worked on that is why the rate of reaction is higher. The more enzymes present the more collision will occur, therefore the more chance of the substrates and the enzymes colliding with each other, which establishes an increase in the number of complexes formed with the enzymes and substrate molecules resulting in an increase of the breaking down going on at the same time. This causes the rate of the reaction to decrease and the breakdown of the starch will be quicker.

A complex…

RATE OF REACTION

Rate of reaction is the time taken for the reaction to take place, in this case it would be used to find the time taken for each individual concentration of amylase and distilled water to break down the starch molecules.

To work out the values for the rate of reaction we use the formula…

Rate of reaction=             Where...   t = time taken for complete breakdown,

If we were to use this formula to find the rate of reaction for all the different concentrations and were to plot a graph, the graph should look like the diagram below.  

Biology textbook … ‘Understanding biology for advanced level’ written by ‘Glenn and Susan Toole’

The V max (maximum velocity) is the physical point where the rate of reaction cannot get any faster. This is because of the limitation of the number of starch molecules available. This limit arises, resulting in a situation where all the enzymes are occupied with substrates there for the remaining substrate molecules have to ‘wait’ for an enzyme to be ‘ready’. This will only occur when there is a larger amount of substrate solution to the ratio of the amount of enzyme solution. This point is shown on the graph above, as the line of values increases to a point where it cannot get any further, therefore continues in a horizontal line as shown.

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Fair test:

In a fair test, it is expected that only one variable changes at a time to see what factors affect the rate of reaction and the experiment.

Temperature-controlled

PH level-controlled

Amount of starch used-controlled

Concentration of amylase enzyme and distilled water-changeable

In this investigation the affect of concentration of an enzyme is being investigated. Make sure that all the apparatus used are washed, so that there is no solution or dirt, etc, to give inaccurate results. Start stopwatch, as soon as the two solutions and water reach 37ºC. To make sure that accurate results are ...

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