Many organisms can decompose hydrogen peroxide (H2O2) enzymatically. Enzymes are globular proteins, responsible for most of the chemical activities of living organisms. They act as catalysts, substances that speed up chemical reactions without being destroyed or altered during the process. Enzymes are extremely efficient and may be used over and over again. One enzyme may catalyze thousands of reactions every second.
At the start of the reaction, there is no product, and the concentration is the same as the atmosphere. After a short time, oxygen accumulates at a rather constant rate. The slope of the curve at this initial time is constant and is called the initial rate. As the peroxide is destroyed, less of it is available to react and the O2 is produced at lower rates. When no more peroxide is left, O2 is no longer produced. Objectives Use a computer and an Oxygen Gas Sensor to measure the production of oxygen gas as hydrogen peroxide is destroyed by the enzyme catalase at various enzyme concentrations. Measure and compare the initial rates of reaction for this enzyme when different concentrations of enzyme react with H2O2. hypothesis Write a 2-part hypothesis that predicts what you think will happen in this investigation and a scientific reason. MATERIALS computer w/ Logger Pro software1.5 H2O2Vernier computer interface - LabProliver enzyme suspension Vernier O2 Gas Sensor10 mL graduated cylinder250 mL Nalgene bottleclock or stopwatch2 pipettes labeled Diagram of procedure procedure Plug in the LabPro to an outlet, then connect the Oxygen Gas Sensor to the LabPro. Connect the LabPro to a computer and prepare the computer for data collection by opening the file 06A Enzyme (O2) from the Biology with Computers folder of Logger Pro. (Macintosh HD(Applications(Logger Pro 3(Experiments(Biology with Computers) Add 6 mL of 1.5 H2O2 to the 250 mL Nalgene bottle. Using a pipette, add 5 drops of enzyme suspension to the Nalgene bottle. Begin timing with a stopwatch or clock. Place the O2 Gas Sensor into the bottle as shown in the labeled diagram of procedure. Gently push the sensor down into the bottle until it stops. The sensor is designed to seal the bottle without the need for unnecessary force. When 30 seconds has passed, Click to begin data collection. When data collection has finished, remove the O2 gas sensor from the Nalgene bottle. Rinse the bottle with water and dry with a paper towel. Do not get the gas sensor wet. Move your data to a stored run. To do this, choose Store Latest Run from the Experiment menu. Repeat steps 2-8 for 10 drops and 20 drops of enzyme suspension. Repeat steps 2-9 three more times for a total of 4 trials. (Actually, you will get data from 3 other groups.) Analyzing the data Make sure you save the experiment file, using the naming convention period_groupletter_liverlab.cmbl. Create an archive of this file by holding down the Control key on your keyboard. Send this to your lab partners and also drop an archived copy into the teachers Classes folder for your class period on the staff server in order to receive copies to be taped into your lab notebook. Using the mouse, select the initial linear region of your data on the graph. Click on the Linear Fit button, . Click and a best-fit linear regression line will be shown for each run selected. In Table 1, record the value of the slope, m, for each of the three solutions. (The linear regression statistics are displayed in a floating box for each of the data sets.) Label all three curves by choosing Text Annotation from the Insert menu, and typing 5 Drops (or 10 Drops, or 20 Drops) in the edit box. Then drag each box to a position near its respective curve. Adjust the position of the arrowhead. Determine the rate of reaction for each of the time intervals listed in Table 2 using the procedure outlined in Step 12. Record the rates for all three data runs in Table 2. DATA Table 1 Drops of Enzyme vs. Slope, or rate Drops of...
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