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Hypothesis: I hypothesis that the enzyme concentration will affect the rate of reaction but only up until a certain point because there is a limited supply of substrate. Enzymes are protein molecule that acts as biological catalyst by increasing the rate of reactions without changing the overall process. They are long chain amino acids bound together by peptide bonds. Enzymes are seen in all living cells and controlling the metabolic processes in which they converted nutrients into energy and new cells. Enzymes also help in the breakdown of food materials into its simplest form.
The reactants of enzyme catalysed reactions are termed as substrates. Each enzyme is quite specific in character, acting on particular substrates to produce particular products. The central approach for studying the mechanism of an enzyme- catalysed reaction is to determine the rate of the reaction and its changes in response with the changes in parameters such as substrate concentration, enzyme concentration, pH, and temperature etc. This is known as enzyme kinetics. One of the important parameter affecting the rate of a reaction catalysed by an enzyme is the substrate concentration, [S].
During enzyme substrate reaction, the initial velocity VO gradually increases with increasing the concentration of the substrate. Finally a point is reached, beyond which the increase in VO will not depend on the [S]. When we plot a graph with substrate concentration on the X axis and corresponding velocity on Y axis. It can be observed from the graph that as the concentration of the substrate increases, there is a corresponding increase in the VO. However beyond a particular substrate concentration, the velocity remains constant without any further increase.
This maximum velocity of an enzyme catalysed reaction nder substrate saturation is called the Vmax , Maximum velocity. Aim: – To investigate how enzyme concentrations can affect the rate of reaction Procedure: 1. Set up the apparatus. 2 Cut 10 discs of potato each 0. 2 mm thick. Place these in the boiling tube with 5 cm3 of buffer solution. 3 Add 5 cm3 of hydrogen peroxide solution to the potato discs. Immediately place the bung and delivery tube firmly into the boiling tube. Place the other end of the delivery tube under the collecting tube. Start a stop clock as soon as the first bubble of oxygen enters the collecting tube from the delivery tube and ollect any gas produced in a three-minute period, 5. Make sure you shake the boiling tube gently throughout the reaction period to keep the contents well mixed. If no gas bubble is produced within three minutes of adding the hydrogen peroxide record a zero value for the test. 6 Measure the volume of oxygen produced in the three-minute period, raise the collecting tube so that the water level water in the tube is level with the surrounding water level in the beaker. Wash out the boiling tube thoroughly. in the most appropriate way. Diagram: EEE Equipment List: – Cylinders of potato tissue – Hydrogen peroxide solution Buffer solution pH 7 – Distilled water – Boiling tube – Bung and delivery tube Beakers – Syringe barrel – Syringes or graduated pipettes Risk assessment: EQUIPMENT RISK PREVENTION Hydrogen peroxide solution Irritate your skin or get into your eyes Wear goggles to protect your eyes and cover your hands and make sure no skin is revealed.
If it does get on your skin, wash hands immediately. Boiling tube Break and pieces could go on your skin Handel with care and if anything does smash inform your teacher and clean up the pieces. Beakers Smash and cut skin pieces as soon as possible. Thermometer / Glass rod Cut skin/ smash pieces. With the thermometer make sure it doesn’t touch anything hot or it will break. Scalpel / craft knife Cut skin / stab yourself When cutting, cut away from you. If you do cut yourself run hand under cold water and cover the cut.
White tile Cut skin and could stamp on pieces Handel with care so you don’t drop it. If it does break get a dust pan and brush and clean it, make sure you don’t cut yourself whilst doing cleaning up the pieces. Water bath Burnt hand Make sure you don’t touch the hot water, if you do and your hand does get burnt Results: Potato Mass (G) Volume of oxygen (cm) 0. 0 0. 1 0. 0. 4 1. 2 0. 6 1. 6 0. 8 2. 1 1. 0 2. 4 Graph: Variables: Independent: The volume of oxygen in the concentration.
Dependent: The time taken for the bubbles to start appearing (3 minutes) Controlled: The temperature, the pH and the hydrogen peroxide solution. Evaluation: Our data isn’t very reliable or valid as we only did one repeat when the minimum number of repeats to make sure your information to do is 3, however if we were given more time we could have done more repeats. Another issue with our experiment was that we rounded the potato mass to the nearest decimal as it would be easier to work with these numbers.