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

Effect of temperature on the action of an enzyme

Extracts from this document...


Effect of temperature on the action of an enzyme Introduction Enzymes are catalysts that speed up biochemical reactions. Most compounds found in cells are very stable and without enzymes would not react at any useful rate. Enzymes are proteins. Their molecular shape is important, because the enzyme needs to form a precise fit with the substrate - the molecule or molecules involved in the reaction. Only a small part of the enzyme makes contact with the substrate; this part is known as the active site. The shape of the active site allows the substrate to fit perfectly, and to be held in place by temporary bonds, which form between the substrate and some of the R groups of the enzymes amino acids. This combined structure is termed the enzyme-substrate complex. The enzyme may catalyse a reaction in which the substrate molecule is split into two or more molecules. Alternatively, it may catalyse the joining together of two molecules, as when making a dipeptide. Interaction between the R groups of the enzyme and the atoms of the substrate can break or encourage formation of, bonds in the substrate molecule, forming one, two or more products. When the reaction is complete, the enzyme is unchanged by this process, so it is now available to receive another substrate molecule. ...read more.


However, if we go on increasing substrate concentration, keeping the enzyme concentration constant, there comes a point where every enzyme active site is working continuously. If more substrate is added, the enzyme simply cannot work faster; the molecules are effectively queuing up for an active site to become vacant. I will keep the substrate concentration at 25cm3, 1.0%. As this is what I used in my preliminary work and it gave reliable and accurate results. Measuring methods The way that I will measure how long it takes for the reaction to cease is to add iodine to a drop of the mixture, it should turn blue if starch is present, if starch isn't present the iodine will not change colour. I will measure the colour change by sight, as the blue colour will vary depending on the amount of starch present. The darker the colour the more starch there is in the mixture. I will use diastase solution (25cm3, 1.0%), and starch solution (25cm3, 1.0%). These solutions proved reliable and gave good results in my preliminary experiment. I could use a colorimeter to be precise, but through my preliminary experiment I found this unnecessary. Prediction I predict that the higher the temperature the higher the rate of reaction. This means that the molecules will move faster and have more energy. ...read more.


5. At intervals of one minute test each tube for the presence of starch-diastase mixture, place it on a white tile, and add one drop of iodine solution. Use one glass rod for each tube and a separate one for the iodine solution 6. Make a complete record of your observations, noting how long it takes in each case before a blue colour ceases to be given when iodine is added to the mixture. I chose this method, as this is the same method that I used in my preliminary experiment so I know it is reliable. Risk Assessment All glassware must be handled with appropriate care, especially when it is immersed in a hot water bath, also take care with the hot water as it is a burn hazard at 100oC. Results Table Temperature (oC) Time (min) Room temp 25oC 40oC 60oC 100oC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 (From my preliminary experiment I found it useful to create a scale for the variation of the colour of the solution when iodine was added. 0 being very dark and 5 being light) The add results to the table you use the scale to find out what number you think best represents the colour and then add it into the correct time row and the correct temperature column. Alan Julyam Biology Coursework Ms Sweeney ...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

    The Effect of Substrate Concentration on Enzyme Action.

    4 star(s)

    This is because more molecules of hydrogen peroxide are available at high concentrations to collide with catalase enzyme molecules, more molecules colliding with sufficient activation energy and more molecules can fit into the active sites of the enzyme molecules by the lock and key hypothesis referred to in the background on page 2.

  2. Marked by a teacher

    How Does the pH of a Solution Affect the Rate of Starch Digestion By ...

    3 star(s)

    the protein is suspended in may cause the ionic charge to change; this is magnified by the number of the residual groups present in every protein so the effect may have a big impact on the shape of the active site.

  1. What effect does the pH have on the enzyme diastase? What effect does the ...

    However, the temperature of 37oC showed the lightest color, which, furthermore, shows that it is the optimum temperature for the diastase enzyme. In this case, the diastase enzyme catalyzed the starch. At 10oC the color is dark, indicating that the enzyme did not work at all; at 20oC the color

  2. To investigate the effect of pH and temperature on the rate of hydrolysis of ...

    This can lead to altered protein recognition or an enzyme might become inactive. A pH that is very different from the optimum pH can cause denaturation. The optimum pH value for most enzymes lies between pH 5 and pH 9.


    Raise the temperature to 30, 40, 50, 60 and 70degrees, whilst looking at the thermometer at eye level. Remember to wear safety goggles and keep well away from the flame. Also take care when handling hot items like beakers and tongs.

  2. Effects of Temperature on the action of Diastase on a Starch Suspension.

    These tubes were then placed back into the water bath, which has been kept constant by adding several drops of warm water to it. 7. As soon as this took place the procedure was timed. The pipette was used to place drops from test tube S into the iodine filled indents on the spotting tiles.

  1. Find out about how the way the reaction between an enzyme (diastase) and substrate ...

    (as I think this will denature the enzyme and therefore the enzyme would not work no matter how much time I gave it as the structure will have changed). I have a simple diagram to show my theory of the temperature affects on the enzyme.

  2. Starch and diastase with respect to pH

    This means that the shape of the acive site changes and so the substratye molecule can no longer bind with the amino acids in the active site. Small changes in the pH do not damage the enzyme irreversably, so if the pH is restored to the optimum pH, the reaction rate will also be restored.

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