IA Yeast/Liver catalase experiment
Students are to investigate something about how the rate is affected by some variable using either Yeast or liver. I am providing the design, student must have their variable approved by me before starting the experiment. No two experiment can be alike. You will work independently on this lab. Pictures will be taken of your set up. Turn in DCP and CE portion of lab.
Background information: In this lab we will observe the action of the enzyme catalase on its substrate, hydrogen peroxide, which reacts accordingly:
2H2O2 ------> 2H2O + O2
The oxygen gas released will be seen as bubbling. We will use a method called the floating disc method to test how catalase activity is affected by such things as temperature, pH and the concentration of substrate. If a small disc of filter paper is cut out with a hole puncher and then soaked in a solution that contains yeast (as a source of catalase), it can be placed in a small cup containing hydrogen peroxide solution, and the oxygen given off will cause the disc to float eventually. Measuring the time it takes the disc to float can be used as a measure of the rate of the reaction: faster reaction rate = faster floating.
You must have approval of your variable and its different levels before starting.
Materials (per group):Small cups pipette
forceps filter paper
hole punchsmall beaker
3% hydrogen peroxideyeast or liver solution
StopwatchHCl, NAOH
Water
Yeast/catalase solution (already prepared for you): 1 tsp. yeast, 1/2 teaspoon sugar, 200 ml water.
Follow this procedure carefully to control variables:
Put 4ml substrate solution into the cup first. Make sure to swirl the beaker of yeast solution before you use it because the yeast will settle to the bottom. Using the forceps, dip the paper discs one at a time into the beaker of yeast/catalase solution for 5 seconds, then place them onto a small piece of paper towel for one minute to remove excess solution. Then, with stopwatch ready, quickly place an enzyme-soaked disc all the way to the bottom of the cup before releasing it. Start the watch when the disc is released at the bottom of the cup, and stop it when the disc first starts to rise from the bottom of the well (as opposed to when it reaches the top). Record the time to the hundredth of a second. Practice a bit before you start recording data.
Clean everything up. Take the cups to the designated bag, not the sink, and dump entire contents; this way no paper discs will clog the sink. Do not throw the cups away Wash and dry the cups. Wipe off forceps. Clean up any bits of paper and return everything exactly as you found it. Wash your hands, with soap, and don’t use too much paper towel to dry them (save a tree, right?).
Due 1/24/14