• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. 14
  15. 15
  16. 16
  17. 17
  18. 18
  19. 19
  20. 20
  21. 21

Investigating the Effect of pH on Enzymes

Extracts from this document...


Investigating the Effect of pH on Enzymes Plan: My aim is to carry out an experiment that will let me deduce the affect that a varying pH will have on the rate at which the enzyme amylase will break down starch into its component parts, which are maltose and dextrins. Background: What is an Enzyme? Enzymes are substances that act as catalysts and so they increase the rate of chemical reactions. In biological systems reactions may occur very slowly or even not at all unless a catalyst is present and this is why enzymes are required. With an enzyme the product of the reaction will occur far faster even to a factor of at least one million. Unlike inorganic chemical catalysts, enzymes are specific. This means that one enzyme normally is used for one reaction. This is as each enzyme has a particular shaped active site, which the substrate (the molecule that is being broken down) will combine with. The shape of the active site depends on the structure of the whole enzyme. The Structure of Enzymes All enzymes are globular proteins, and so have a primary secondary and tertiary structure. The primary structure of a protein is the number, type and sequence of amino acids that make up a polypeptide chain. In the case of the enzyme that we are using (alpha-amylase) the polypeptide chain is around 496 amino acids in length. Each of these amino acids has the general formula NH2.RCH.COOH, where the R group varies giving the 20 different individual amino acids. Two amino acids join together in a condensation reaction, where a molecule of water is removed, forming a dipeptide. The bond that joins them is called a peptide bond; more and more of these are formed forming polypeptide chains. The secondary structure is where these polypeptide chains arrange themselves into another shape, which could either, be into a spiral shape, the alpha helix or into a corrugated sheet structure called a beta pleated sheet. ...read more.


5 1 in 25 40 x 10-2 18 18 18 9 + 1 1 in 11. 1 1 in 22.2 45 x 10-2 14 14 14 ('-' Indicates that this concentration was not measured as only a certain number were needed to produce an accurate curve) From these results a graph plotting final concentration to average transmission can be produced. This is the calibration curve and it will allow me to read off unknown values of maltose as long as I know the percentage transmission. The calibration curve itself is in the analysis section of this investigation. Main Experiment Method (Implementing): The method used in the main experiment is much the same as that used in the preliminary experiment, as a water bath will be set up using a tri-pod, Bunsen burner and a heat proof mat. The beaker will be the 500cm� volume, so as to fit the 7 boiling tubes for the seven-pH values that are being used. This will be filled with water and left to boil. Once it has begun to boil a 5cm� sample of Benedict's solution will be placed into 7 boiling tubes using a graduated 5cm� pipette and pipette filler. Tin foil will then be placed over the tops of the boiling tubes to stop any of the Benedict's solution evaporating away. They will then be marked with the pHs that are being used (2.2, 4, 6, 7, 8, 9 and 11) with a marker so they can be identified when they are take out of the water bath. These will then be placed in the hot water bath all at the same time so they would boil at the same rate. At the same time 2.5cm� samples of the stock amylase solution made in the preliminary experiment (which had been refrigerated for a short time) will be taken using a 5cm�-graduated pipette as a 1cm� one would mean three measurements so increasing the risk of an error, and this sample placed into 7 different test tubes. ...read more.


To get this you would have to carry out the experiment again and again, possibly using the refinements highlighted above, and although the equipment was there the time this would have taken made it impracticable. This point very clearly shows that one investigation cannot be used alone to prove a set of results and shows that the conclusions and results obtained should be dealt with tentatively. To further my investigation, aside from repeating the same experiment to give more results that would serve to either back up the conclusions found ion this investigation or undermine them, would be to focus in on the optimum value for pH. It was found that pH 7.3 was the optimum temperature, but was only an approximate as the range of values is large. To more accurately find the optimum temperature pH solutions could be made up, such as 6.8, 7, 7.2, etc. The same method used in the main experiment with the changes suggested earlier in this section could be used and the results would produced the same sort of curve but would be much broader and would allow the optimum temperature to be found more accurately. From this smaller range of results you would also be able to deduce more effectively the effect that the change in pH has on genetically engineered amylase, as you will be able to see the effect of changing the optimum pH in small increments and use these results in conjunction with the results obtained in this investigation to see how sensitive amylase is to a change in pH from its optimum pH, i.e. whether small changes in pH do not have much effect shown by the graph further investigation having broad sides or whether small pH changes are significant shown by the graph having steep sides showing greater drop in activity, and with a more accurate optimum pH the conclusions are likely to be more reliable. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Molecules & Cells essays

  1. Marked by a teacher

    effect of concentration of copper sulphate on the action of amylase to break down ...

    4 star(s)

    crystallography and computer assisted modeling [73], we can say that the active site is actually not a perfect fit to the substrate. So when the substrate approach the active site, either the shape of the substrate or the shape of active site will change slightly so they can fit precisely together.

  2. Marked by a teacher

    How does the concentration of enzymes affect the breakdown of starch by a-amylase in ...

    4 star(s)

    Avoid ingestion or inhalation of the enzyme granules. In order to avoid all contact with eyes or skin, gloves, lab coat, and safety glasses will be used at all times while handling the enzyme concentration solutions. Spilled preparation should be removed immediately.

  1. Marked by a teacher

    The Effect of Substrate Concentration on Enzyme Action.

    4 star(s)

    Rubber Tubing Small Beakers Gas Syringe Conical flask with delivery Stand tube Conical Flask Stopwatch Glass rod Plastic syringes Method 1. Start by making the yeast concentration of 2% by mixing the yeast with 100mls water. 2. Make the hydrogen peroxide concentrations, 20%, 40%, 60%, 80% and 100%.

  2. Marked by a teacher

    How does the pH affect the activity of amylase

    3 star(s)

    + + + + + + + + + + + + + + + + 5 + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 6 + +

  1. Marked by a teacher

    Investigation of factors affecting the enzyme Amylase.

    3 star(s)

    All the quantities will have to be carefully measured since small variations in the amount of enzyme used can make significant variations in the results. In the experiment where temperature is investigated, 2cm of water is added. This is because the starch solution is neutral and in the previous investigation (for pH)

  2. An Investigation Into the Effect of Substrate Concentration On the Rate of Enzyme Activity.

    jelly, the results of the experiment may not be correct in that the active site do not get denatured easily so the optimum temperature is substantially higher than was expected. To investigate this further, the sodium alginate beads with yeast catalase suspended in them were replaced with discs of filter paper soaked in non immobilised yeast catalase.

  1. Investigating the effect of temperature On the action of Amylase on Starch.

    We will then record the amount of time taken for the iodine to stop changing colour. 14. This shows us how long it took the Amylase to break down the starch. 15. We will repeat this process three times for each temperature.

  2. How does pH affect the Denaturation of enzymes Starch and Amylase.

    starch broken down by amylase, so I have something to compare with. The variable that I will have will only be the pH. Every other factor, the volumes, concentrations and temperature, (presuming that the room always stays the same temperature)

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work