• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Determine the extent to which a pH affects enzyme effectiveness.

Extracts from this document...

Introduction

The aim of this investigation is to determine the extent to which a pH affects enzyme effectiveness. This was measured via absorbency techniques, using the colorimeter. Apparatus Water Bath set to 40�C Colorimeter Cuvettes Test tubes 10ml measuring cylinders Glass pipette Small and large beaker Tweezers Test tube rack Thermometer Live enzyme (pepsin 2%) Denatured enzyme Buffers, 2, 3, 4, 5, 6, 7, 8 Stop watch Marker pen Strips of 35mm x 5mm photographic film Sticky Labels Safety * Wear lab coat * Wash your hands thoroughly before and after the experiment. * Never eat or drink in the lab * Report any accidents, breakages or spillages * Wear goggles throughout the experiment and take precaution when handling the acidic buffers. Method * Two sets of test tubes were labelled 2, 3, 4, 5, 6, 7, 8 respectively1. * All the test tubes were placed in the rack, ready for solutions to be added to them. * Using a 10ml measuring cylinder 3ml of pepsin and 3ml of pH 2 buffer were accurately measured using separate cylinders2. * This was repeated for the rest of the pH buffers 3, 4, 5, 6, 7, 8. ...read more.

Middle

This shows that the solution contains the most precipitate, and thus, the optimum pH must be 3. The absorbency levels drop rapidly either side of this value, however, much more significantly closer to pH neutral and basic conditions. Evidently, the effect is more significant the more the pH deviates from pepsins optimum pH 3. This indicates that it has altered the ionic bonds, which help to determine the tertiary structure of the protein. This has lead to distorted protein recognition. As a result, pepsin was unable to break down the gelatine, which binds the silver halide salts to the photographic film. The graph indicates that the enzyme has become completely inactive, or denatured, by the time the pH is 8 as there is a absorbency of 0 on average. Spearman's rank correlation is used to determine if an association exists and also the strength of the association. If one set of measurements increases as the other decreases, they are negatively correlated. A perfect negative correlation has a value of -1. This value can then be compared with the critical value of r according to the number of pairs of measurements. If r is greater or equal to the critical value then the null hypothesis can be rejected, and it can be evaluated that a significant correlation exists. ...read more.

Conclusion

The heat gives the enzymes added kinetic energy and so increases their movement and therefore, their activity. 6 Tweezers are used to prevent contamination by the hands. 7 The photographic film was added in 20 second intervals so that they may be removed in 20 second intervals, thus spending an equal amount of time in the soulutions. This makes the results more reliable as it is a fair experiment. 8 A stopwatch is used as this is an accurate measurement of time 9 The films are left for this amount of time so the enzymes have opportunity to degrade the substrate and a better difference of effectivity becomes more obvious in the resukts. 10 This ensures that the photographic film is left inside the solutions for an equal amount of time. Making the test fair and results more reliable. 11 The solutions were shaken to suspend the black silver bromide crystals. This ensures that they do not sit at the bottom of the test tube. 12 When putting anything in colorimeter assure that the lid is firmly closed so no excess light can enter and effect results ?? ?? ?? ?? Ashleigh MacDonald Investigating the Effect of pH on the Activity of an Enzyme ...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

    To determine the optimum pH for two different proteolytic enzymes.

    4 star(s)

    Since it measures a fraction, the larger the pH number, the less H ions are present in a solution. Pepsin is an enzyme produced from pepsinogen that initiates protein digestion by breaking down protein into large peptide fragments. An enzyme, produced by the stomach, that chemically breaks down peptide bonds in polypeptides and proteins.

  2. A2 coursework- The effects of bile salts on digestion of fat

    lipase will not be breaking down the fat as quickly and so temperature will become an independent variable in this experiment. I found from my preliminary work that using a water bath worked well and it will keep the temperature more constant then a Bunsen burner which will also be

  1. Investigating the Effect of pH on Enzymes

    + 5 1 in 20 1 in 40 25 x 10-2 30 32 31 6 + 4 1 in 16. 6 1 in 33.3 30 x 10-2 24 23 23.5 7 + 3 1 in 14.2 1in 28.4 35 x 10-2 - - - 8 + 2 1 in 12.

  2. Spreadsheet report

    I changed the 40% which was in the cell to 50%, pressed enter which made the numbers in every table change. Mark up 50% These were the profits per week before the mark up was increased. PROFITS EACH WEEK Week 1 �1,589.93 Week 2 �1,312.12 Week 3 �1,309.36 Week 4

  1. A photographic company wants to recycle the plastic in exposed (and therefore unusable) photographic ...

    This means that the photographic film will stay opaque. Reasons One of the main reasons for my prediction is the collision theory. The collision theory is based on the knowledge that chemical reactions take place by probability. In order to react, particles need to collide in the right course with enough energy to overcome the activation energy.

  2. Cost effectiveness of mainstream bench cleaners against generic supermarket cleaners on the number of ...

    A swab will be taken, before and after the addition of the antibacterial spray and the percentage decrease in the bacteria can be found by counting the number of bacteria before and after the spray has been used. This is a real life situation and examines the effect on bacteria found on workbenches.

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