• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11
  12. 12
    12
  13. 13
    13
  14. 14
    14
  15. 15
    15
  16. 16
    16
  17. 17
    17
  18. 18
    18
  19. 19
    19
  20. 20
    20
  21. 21
    21
  22. 22
    22
  23. 23
    23
  24. 24
    24
  25. 25
    25
  26. 26
    26
  27. 27
    27
  28. 28
    28
  29. 29
    29
  30. 30
    30
  31. 31
    31
  32. 32
    32
  33. 33
    33
  34. 34
    34
  35. 35
    35
  36. 36
    36
  37. 37
    37
  38. 38
    38
  39. 39
    39
  40. 40
    40
  41. 41
    41
  42. 42
    42
  43. 43
    43
  44. 44
    44

How do temperature and concentration affect the rate of decomposition of hydrogen peroxide by the enzyme catalase?

Extracts from this document...

Introduction

How do temperature and concentration affect the rate of decomposition of hydrogen peroxide by the enzyme catalase? Aims: This is an experiment investigating how the concentration of hydrogen peroxide (substrate) and temperature affect the rate of reaction of the enzyme catalase. Introduction An enzyme is a globular protein found in living cells, they have the ability to catalyse an experiment, therefore they are often used to speed up reactions that don't happen fast enough naturally. Enzymes speed up a reaction by lowering the activation enthalpy (Ea), thus meaning that more collisions between substrate molecules and enzyme molecules result in a reaction, see fig 1 below to see how the activation enthalpy of an experiment varies in the presence of an enzyme Fig. 1: How Ea varies when a catalyst is and isn't present The graph shows that when there is no enzyme present then less of the molecules possess the activation energy so fewer collisions between particles will results in a reaction, however when the enzyme is present more of the molecules have the activation energy so more collisions results in a reaction. All enzymes are specific, they are only able catalyse one or possible a few substrates. Enzymes can recognise its substrate from even isomers, they are that specific. This is because of its three dimensional shape. Only a small part of the enzyme binds with the substrate, this is the enzymes active site. The active site is formed from a few of the enzymes amino acids. Enzymes are specific because the substrate has to fit into the enzymes active site. As the substrate enters the active site, the enzyme changes shape slightly so that the substrate fits in the active site tightly to form an enzyme-substrate complex. Weak hydrogen and ionic bonds bind the substrate and enzyme. The enzyme-substrate complex brings chemical sites from the enzyme in a better position to break down the substrate. ...read more.

Middle

Final method 1. Set up apparatus and water bath. 2. Measures out 2ml yeast with graduated pipette and put into conical flask, place resealable bung on top of flask and join up delivery tube to sidearm. 3. Measure out 4ml hydrogen peroxide into syringe and push hypodermic needle through resealable bung. 4. Inject in hydrogen peroxide and start stop clock. 5. Time for 90 seconds, measuring every 10 seconds recording results in a table. 6. Repeat 3 times for each variation of temperature and concentration. I will also carry out a titration of hydrogen peroxide; this will enable me to find out the concentration of the stock hydrogen peroxide solution (20-vol) that I am using I will be carrying out five titrations to enable me to get a reliable average for my calculations. The method for this is shown below: 1. Take 25ml of 20-vol H2O2 into a graduated flask and top up to 500 ml with distilled water. 2. Remove 25 ml of this new solution and add 200 ml of distilled water and 25 ml of sulphuric acid (1 molar). 3. Then take 25 ml of this solution into a beaker and titrate with 0.005 mol dm-3 potassium manganate from a burette, making a note of the value that the manganate solution goes up to. 4. When the solution retains its pinkish colour the titration is complete. Now take the new reading from the burette and subtract the starting volume from the end and I now have my titre. Results Below is a list of tables and graphs for each varied temperature, during these concentrations the hydrogen peroxide used always came from the stock solution (20-vol), it was not diluted: Temp- -5oC Amount of O2 collected (cm3) Time (seconds) 1 2 3 Average 0 4.0 4.0 4.0 4.0 10 8.0 7.5 4.0 6.5 20 13.0 12.0 5.0 10.0 30 20.0 16.5 10.0 15.5 40 27.5 22.0 16.0 21.8 50 31.5 27.0 21.0 26.5 60 37.0 31.5 25.0 31.2 70 42.0 35.5 29.0 35.5 80 46.5 39.0 33.5 39.7 90 49.5 43.0 37.0 43.2 Temp at end (oC) ...read more.

Conclusion

The gas is due to air displacement when we inject the hydrogen peroxide into the conical flask, we inject 4ml of hydrogen peroxide so an equal volume of air is displaced into the gas syringe. This happens for every experiment and the volume displaced is the same each time because we always add the same amount of hydrogen peroxide, therefore it doesn't alter my results or affect my graphs. One last variable that I was unable to control was the temperature of the room. As the experiments where I varied the temperature were carried out in a water bath fluctuations in room temperature wouldn't really affect them. However, the experiments where I varied concentration were carried out on the desk so these may get affected. If the room had heated up during the experiment it would have speeded up the rate of reaction due to the molecules possessing more kinetic energy, colliding more often and more of these collisions resulting in a reaction. If the temperature had of decreased then the opposite would have happened, the molecules would have less kinetic energy, less of them would possess the activation energy, so they would collide less often and less of the collisions would result in a reaction. If there were any temperature changes during my results it would make them unreliable, as the solutions would have different levels of energy. For example if there was a temperature increase at the beginning of the experiments, as I carried out the higher concentrations first the rate of these experiments would be increased. Then if the temperature went to normal the middle set of experiments would have the expected rate of reaction, and if it decreased further the last experiments I carried out would have a lower rate of reaction than expected. However I don't think that this happened because my tables of results and graphs seem to be accurate, and follow my prediction. Chemistry coursework Yr 13 Major Project Carl Ahuja Page 4 of 44 ...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

    Investigating the breakdown of hydrogen peroxide using celery tissue to supply the enzyme catalyst

    4 star(s)

    Therefore the rate of reaction is slower when the concentration is higher. Evaluation The data that I collected was fairly reliable, but there was one anomalous result. This is shown on each of my graphs. This anomalous result was the first result collected when doing my experiment.

  2. Marked by a teacher

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

    4 star(s)

    distilled water The agar plates again have been left in the incubator/oven for a period of 24 hours at the same temperature of 26�C. A well diameter of 14.2mm was maintained for all the holes. The results are shown in the table below: Concentration of the enzyme solution (%)

  1. Marked by a teacher

    Enzymes - investigate how the substrate concentration (H2O2) affects the activity of catalase on ...

    3 star(s)

    Delivery tube 1 Use to allow gas produced to go to burette. Plastecine - Use to make top of bungs airtight. Rubber bungs 12 Use to cap dilutions of hydrogen peroxide solution until use. Catalase 50 cm3 Use to catalyse hydrogen peroxide solution. Liquidiser 1 Use to liquidise catalase solution.

  2. Marked by a teacher

    Beetroot Practical Write up

    3 star(s)

    Thus, they can lose an H+ ion at the COOH part of the molecule at higher pHs, or gain an H+ ion at the NH2 end of the molecule at lower pHs." Therefore the overall shape of the protein molecule changes because of this change in the pH.

  1. The effect of Copper Sulphate concentration on Catalase activity on Hydrogen Peroxide.

    If ingested it could cause serious damage to our internal organism. It is vitally important that goggles are worn throughout the experiment, which would prevent the solution from entering in contact with the eyes, which are a very delicate part of our body and likely to be irreversibly damaged.

  2. To investigate the rate at which hydrogen peroxide is broken down by the enzyme ...

    I shall measure all the volumes that I am using, using varying glass pipettes of appropriate sizes. Apparatus: * 250.0cm� of celery extract containing catalase * 500.0cm� of hydrogen peroxide * 250.0cm� of distilled water * Stop watch * 250.0cm� conical flask * 3 x 250.0cm� beakers * Bung with

  1. WHAT EFFECT DOES SUBSTRATE HAVE ON THE RATE OF RESPIRATION IN SACCHAROMYCES CEREVISIAE?

    pH I will dissolve the saccharomyces cerevisiae and substrate in a buffer solution. Such a solution resists changes to pH maintaining a constant pH, in this case, a pH of 6.5 Like temperature, pH is a factor that influences enzyme activity.

  2. Catalyse Investigation

    Variation of temperature - In this investigation, I measured the rate of hydrolysis of sucrose by the enzyme, sucrase at varying temperatures. These temperatures were 22�, 30�, 35�, 40� 45�, 50�, 55�, 60�, 70� and 100�C. Although this is a fairly good range of temperatures, it is still difficult to conclude an exact optimum temperature for the sucrase enzyme.

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