What effects do 5 different temperatures that fall within the range of 10°C to 45°C, have on the oxygen gas produced in a catalase reaction, where the enzyme catalase is excreted from the potatoes kept at room temperature, further mixed with substrate hydrogen peroxide, to produce oxygen, which is measured by a gas pressure sensor over the period of 3 minutes?
This experiment will investigate the effect of temperature on the rate of reaction which will be calculated by measuring the rate of the production of oxygen gas. In this experiment, the production of oxygen gas will determine the rate of reaction through the change in pressure as the reaction progresses, in 5 different temperatures. The rate at various temperatures will be found by calculating the slope of pressure vs. time graph. Gas pressure inside the test tube will increase or decrease depending on the amount of oxygen gas produced over the time period of 3 minutes. If the graph has a steeper line/ slope is large value, the rate of reaction is fast, and if the graph has flat slope, and the value is small, the rate of reaction is slow. This experiment helps determine which temperature range results in high reaction rate, and which temperature range results in low reaction rate for catalase.
Background information: Biological catalysts are enzymes that increase the rate of reactions without themselves being chemically changed during the reaction. Enzymes are proteins folded into a complex 3-dimensional shape that contain a special surface area called the active site where a specific substrate binds to it structurally and chemically. Enzymes speed up reactions as they lower the activation energy, which is the minimum energy needed to be overcome before a reaction can occur by providing an alternative reaction pathway.
In this experiment, the enzyme that will be used is catalase. This molecule is commonly found in animal and plant cells, and it is found in a nutritious plant called potato. The substrate that will be catalyzed is hydrogen peroxide (H2O2) which is a poisonous waste product in the human body. Therefore, the catalase enzyme will catalyze the hydrolysis reaction of H2O2into safe, non-poisonous products of water and oxygen gas:
2H2O2O2 + 2H2O
Since enzymes are proteins, they can be easy denatured. If the temperature becomes too high, the amino acids in the enzyme protein will vibrate to break down the intramolecular bonds. This results in the denaturation of the enzyme, meaning the structure of the protein has changed so that the substrate can no longer fit into the active site, making it dysfunctional. This denaturation occurs when the temperature of the enzyme exceeds the optimum temperature of 37°C and results in decreasing rate of reaction. The hypothesis is that 37°C is the optimum temperature where catalase activity will occur at the fastest rate because the human body also functions best at 37°C. Once the temperature of catalase exceeds 37°C, it will denature and H2O2molecules would not be able to fit into the active sites and start decreasing the rate of reaction. Reasonably from approximately 50°C, there may be no reaction at all, because by then all catalase will be denatured completely.
Independent variable: The independent variable in this lab are the different temperatures at which the reaction will take place. A change in temperature causes a change in the reaction rate of an enzyme. As the optimal temperature for enzyme reaction is 37.5° C (which is the normal body temperature), this means that the enzyme reaction here will be at the fastest rate, but as the temperature drops or increases from the optimal temperature the enzyme reaction rate will start to decrease. Both solutions (catalase, and H2O2) will be poured in test tubes and will be placed in water beaker cooled and heated to 10°C, 22°C (room temp), 30°C, 37°C, 45°C to change the temperature and maintain it constant throughout each trial.
Dependent variable: The dependent variable in this lab is the rate of reaction. The change in temperature directly affects the rate of activity of the enzyme, by changing the structure of the enzyme. This is because all enzymes are protein based, a change in temperature changes their shape, and makes them unfunctional. In the lab, rate of reaction will be measured by gas pressure sensor, which is used to measure gas pressure (in this case it will be oxygen gas). A rubber stopper is used to ensure a closed system inside the test tube where reaction is taking place. Gradient/slope of the change of pressure for the initial 180 seconds is the rate of reaction. 5 measurements are made for each temperature to reduce random error.
Controlled variable: The controlled variable in this lab are substrate (H2O2) Concentration and Quantity, amount of Enzyme (catalase), time (min), temperature THROUGHOUT each trial, size/Volume of Test Tubes, pH of solutions, and type of Plant (source of catalase). With the use of same pipette all trials will use exactly the same amount of, and catalase solution. Each trial will collect data for 3 minutes after theH2O2 is poured into the catalase solution. An automatic timer will stop recording the gas pressure once 3 minutes have been reached. Temperature must be maintained constant for 3 minutes throughout all trials. Trials will take place inside a cold water breaker, hot water beaker, or at room temperature where the temperatures of the solutions are equivalent to the temperature of the surroundings so to maintain a constant temperature. A thermometer will be placed inside the water beaker to ensure that the temperature remains constant and does not fluctuate. All test tubes used in this experiment will have the same diameter, length, and size to maintain a constant volume. Variance in volume would change the pressure inside the tube for equivalent gas production amount.Catalase solutions for trials are from the same original catalase solution so all trials will have the same pH level.
Uncontrolled variable: The uncontrolled variable in this lab are some human errors which include not closing the test tube immediately after the H2O2is poured in. This can cause uncertainty in the data collected. As some gas produced has escaped from the test tube. There can also be error/ technical problem with the gas pressure sensor, or the labquest device. It might not give the right readings, and the slope value. This can completely throw off the data calculations, and the end result.
Control of variables: In this experiment the variables are kept under control, by using various equipments. As listed above, the concentration and amount of H2O2will be kept constant with the use of same pipette. Each trial will collect data for 3 minutes/ 180 seconds after theH2O2 is poured into the test tube, which contains catalase solution. An automatic timer will stop recording the gas pressure once 3 minutes have been reached. Temperature is maintained constant for 3 minutes throughout all trials, using thermometer. Trials will take place inside a cold water breaker, hot water beaker, and at room temperature where the temperatures of the solutions are equivalent to the temperature of the surroundings so to maintain a constant temperature. A thermometer will be placed inside the water beaker to ensure that the temperature remains constant and does not fluctuate. All test tubes used in this experiment will have the same diameter, length, and size to maintain a constant volume. Variance in volume would change the pressure inside the tube for equivalent gas production amount. Catalase solution obtained from potato is used for all trials so all trials will have the same pH level. The potato is thoroughly washed and peeled in order to wash off any dirt or impurities.