• 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

The effects of temperature, PH value, substrate & enzyme concentration and those of inhibitors and cofactors are of particular biological interest and can be summarized as follows:-

Extracts from this document...


Enzymes are globular proteins and within the cell they have two fundamental roles: > They act as highly specific catalysts, greatly speeding up chemical reactions which would otherwise be hopelessly slow > They provide a mechanism whereby individual chemical reactions can be controlled, the available quantity of an enzyme determine the rate of the corresponding reaction. At the moment, hundreds of chemical reactions are in progress in a typical living cell. Theses reactions provide energy and help to maintain supplies of the many different substances needed for growth & repair. The remarkable fact that all these reactions contribute to an organized overall metabolism is due almost entirely to the production of special substances called enzymes. You can see from the fig that the specificity of an enzyme's action arises because each enzyme has a definite three dimensional shape which is complementary to that of its reacting molecules, or substrates. The first step in any reaction catalyzed by an enzyme is the formation of a specific association between the molecules called an enzyme-substrate complex. This is made possible by the fact that the configuration of the enzyme matches the shape of the substrate over a relatively large area called active center of the enzyme. ...read more.


At the other extreme, the ice fish of Antarctic waters has enzymes which function efficiently at -2�C. Most enzymes have an optimum pH close to pH 7, which is the normal intracellular pH. This is illustrated in the figure. Enzymes which work extra cellularly can have very different pH requirements. A notable example is the enzyme pepsin which is found in the stomach and works best in highly acidic conditions in the range pH 1 - 2 pH changes away from the optimum can affect enzyme activity adversely in either of two ways. In cases where the binding or catalytic sites within the active centre take the form of charged ions, some values of pH are inhibitory because they cause these ions to re associate. The uncharged groups formed as a result can no longer interact with the substrate & so catalytic activity is lost. A second possibility is that the enzyme molecule can change shape and become denatured: this is more likely to happen at extreme values of pH which tend to weaken the forces holding the enzyme molecule together. In my course work, I am investigating the effect of temperature on the activity of enzymes. ...read more.


prepare a syringe full of hot water so as the temperature goes down we can add water from the syringe to maintain constant temperature needed for fair comparison. We could use sensitive balance to measure the mass of the potato discs used in the experiments so we can have more accurate results needed for fair comparison. Using suitable length of the connecting tube so as not to have a lot of air inside it which would affect the accuracy of the experiment & also a suitable size of a measuring cylinder so as we can see the small differences I think that further investigation is needed to use wider range of temperatures and more accurate equipments to obtain more accurate results. : It is obvious that there were sum errors in my experiments as on using temperature 20�C as more oxygen was released more than predicted & I think that was because of the air inside the tube as heated and expanded & made more air released. I think that some oxygen was lost in the time between putting the hydrogen peroxide & closing the stopper over the test tube. But I think that I did my best to have the most accurate results I could obtain. ?? ?? ?? ?? ...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

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

    4 star(s)

    Looking from the 2% value onwards, it is quite evident that there is an almost perfect line going though the points. This suggests that there is a fairly steady increase, which means that there must be a fairly constant increase in the rate of breakdown of the starch molecules.

  2. Investigate how concentration of the enzyme catalase in celery tissue alters the rate of ...

    it is easy to accurately use a syringe and to see any bubbles in the solution. I realised after the experiment that by tapping the syringe, or flicking it, the bubbles would rise to the top, so bubbles can be pushed out.

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

    and so there are more enzyme-substrate complexes than at any other time of the reaction. However as time goes on there comes to point where the rate of reaction is constant due to a limiting factor. The limiting factor in this instance is concentration of enzyme "there comes a point

  2. An Investigation into the Effects of Temperature on Enzyme Reactions

    The Albumin hopefully does not contain any anti- enzymes that will prevent a reaction between it and the Trypsin. This is what must be found in the preliminary experiment. Preliminary Work A preliminary experiment was performed to test that there was actually a reaction between the Trypsin and the Albumin.

  1. Germination Inhibitors

    These data from the mean values of the group results suggests that the 100% tomato juice did have an effect on the lettuce seeds, and that the dormancy was prolonged, inhibiting germination. The standard deviation data suggests a measure of the dispersion, therefore I can evaluate 100% tomato concentration induces the least amount of germination.

  2. Design an Experiment to Determine the Effects of Copper Sulphate Concentration on the Germination ...

    The main elements needed by plants are nitrogen, phosphorus, potassium, calcium, magnesium, iron, boron, zinc, manganese, molybdenum and copper. These elements need not be pure but come from compounds of minerals. Plants need copper for processes such as, photosynthesis, respiration, protein synthesis, lignification of cell walls and the formation of pigments.


    extracellular fluid, synthesis of the enzymes that would enable the cell to produce that amino acid for itself is shut down. Conversely, if a new substrate is made available to the cell, it may induce the synthesis of the enzymes needed to cope with it.

  2. An Investigation to determine the effect of Substrate Concentration on the Enzyme Catalase

    Bonds that hold the polypeptides in specific shapes are broken and the shape of the active site changes, so substrate molecules no longer fit. At Q, the enzyme is denatured and loses all activity. pH Most enzymes work over a narrow range of pH.

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