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Effect of Concentration of Substrate on Enzymes

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EFFECT OF CONCENTRATION OF SUBSTRATE ON ENZYMES AIM - To find the effect of 'concentration of substrate' on an enzyme controlled reaction and HYPOTHESIS - To prove the hypothesis: as the concentration doubles so does the rate of reaction, A point is reached however, where all sites are being used and by raising the substrate concentration the rate won't increase as the limiting factor is the amount of enzymes. RESEARCH - A test that could be done is timing the speed of a reaction with obvious end results. In most instances it is hard to record the exact finish. The reactants being used are hydrogen peroxide and the Enzyme - Catalase. This reaction produces O2 and H2O. These are not easy to see being made and a way is needed to facilitate this. pH is hard to measure to see the H2O2 change to neutral. A colorimeter could be used for accurate colour tests, but not for an accurate time scale as there would be time lapses between testing and getting the colour change. It is hard to see the change at exactly pH7. When pH changes from 4 to 6 it's on a very steep part of the graph showing pH change... If phenaphalin (an indicator that changes at pH 8) is used (or another indicator that changes at pH 7 of after) ...read more.


The more H+ bonds in the substance the more hydrogen bonds in the enzyme are broken. The H+ ions break the positive-negative bonds in the enzyme molecule and change its shape. The active site does then not fit the substrate and the reaction can't take place. The pH can be monitored using universal indicator. Using a buffer could control the pH, a buffer solution contains either a weak acid and its salt, or a weak base and its salt. The acid provides H+ ions when the pH rises (goes alkali) and the salt (mainly - the acid does provide some) provides - ions depending on the chemical structure . E.g.. H2CO3 (aq) = H+ (aq) + CO3- (aq) The - ions would be the CO3 from the salt. The + ions would be the Hydrogen from the acid. Then H2CO3 would be formed again. Certain buffers are used in different situations so reactions can be kept at a certain pH. The pH of this reaction gets lower due to the H2O2 being acid and the end product, water, being neutral. The enzyme Catalase can work in these conditions so its not going to denature. Therefore the pH would be seen (if indicator was added) to rise during the experiment the end pH if the experiment was left to complete being pH7. The temperature may rise due to the energy being produced in the reaction. ...read more.


is added by the same method (using a different syringe) to the boiling tubes. The syringes should be labelled with semi-permanent pen to prevent contamination. H2O2 (ml) H2O (ml) 2 8 4 6 6 4 8 2 10 0 3. The apparatus has to be set up as in diagram. The clamp stands and boss heads are used to hold the apparatus steady and upright. To fill the tubing with water run a bath/sink of water and submerse the whole tube until it is 1/2 full. This may take some time as if it is too full all of the water must be poured out otherwise air bubbles will form. 4. The hydrogen peroxide solution being used is poured into the conical flask. The bung (covered with Vaseline) is placed in the conical flask and the water line is marked with semi-permanent pen. A line 3 cm above it is also marked. 5. 10ml of yeast is added to the chonical flask using a 10ml syringe (line on the bottom of the meniscus) . The bung is put in (covered with Vaseline) and the stop clock started. Help is needed for a fairer/more accurate test. 6. The reaction is timed until the water has risen by 3 cm (when the bottom of the meniscus in the tubing is resting on the second line.) 7. All concentrations are repeated three times. By looking at the results it is possible to see anomilies and these will then be repeated again to give better averages. 8. A rate ( against concentration graph is plotted. ...read more.

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