Title: The Effect of DIfferent Substrates on Glycolysis in Yeast
1. To measure the amount of carbon dioxide produced using three different substrates.
2. To estimate the rate of respiration in each case using data processing.
3. To link the theory of respiration with our knowledge of carbohydrates.
Glycolysis is the process by which glucose is converted into pyruvate. This ultimately forms pyruvic acid, which is used to supply energy to living cells. More about glycolysis can be found on BioNinja.
Preparation is Key. So today (12/7/16), we will spend part of the period prepping for your lab. You need to clean and label your test tubes. I will provide hot water so that you can make sure they are clean. Dry them with paper towel. Use a metric ruler and measure 3 cm from the bottom of the tube and draw a line using a Sharpie. Do this for 4 test tubes. Number them 1, 2, 3 and 4.
Put your test tubes in the rack and using a post-it, write your names on your test tubes and put them in a safe space. You will be given your bag of flour (which is 20 spatulas' worth), labeled cups, and a spatula to keep with your materials. If you do this today, then you will be ready to begin the lab on the next day.
Read through the handout and form a hypothesis about what may happen and why. This is your ticket out the door for today. You need to get it checked off by me, as it is going into the gradebook as a classwork assignment.
You will be working in groups of 4. Put all group members' names on the post-it.
On the handout is the template for the data you will collect. We will be working with limited equipment, so we will do the best we can. You will have to share the electronic balances.
1. Take 4 test tubes and measure 3cm from the bottom. Mark it on the test tube with a Sharpie. Number them 1 2 3 and 4.
2. Label your cups like so: 1. STARCH 2. SUGAR 3. GLUCOSE 4. CONTROL For the 5th cup, label it MIXTURE, as you'll be mixing your yeast and flour in this cup.
3. Measure 75mL of warm water using the graduated cylinder and pour it into the MIXTURE cup. Add 4g of yeast to the MIXTURE cup. Stir gently.
3. Carefully pour all of the flour to the yeast/water mix and stir gently. It will be somewhat loose.
4. Split the dough into 4 equal portions using the spoons. Put each portion into one of the labeled cups.
5. Clean your spoon.
6. To the "STARCH" cup, add two spatulas' worth of cornstarch. Stir gently
7. To the "SUGAR" cup, add two spatulas' worth of sugar. Stir gently
8. To the "GLUCOSE" cup, add two spatulas' worth of glucose. Stir gently
9. DO NOT ADD ANYTHING TO THE "CONTROL" CUP!!
10. You and your partners should (at the same time) add 3cm of dough from the labeled cups to the matching numbered test tube and mark the height of the dough. Start timing. One person should be watching and timing one test tube. For example, Hala should observe and time the STARCH tube while Lamya observes and times the SUGAR tube.
11. Measure the height of the dough in the test tubes every 3 minutes starting at t = 0. Stop after 18 minutes, or 21 minutes if the dough rises slowly. Time in minutes is your X-axis. Dough height in centimeters is your Y-axis.
12. While you wait, document the materials used and make notes on the uncertainties of the equipment (I'll tell you this part). Also document any observations (color, smell, sound, condition of test tubes, etc. This is your QUALITATIVE DATA, which goes before quantitatiave data in the lab report.
You will have to use hot water to wash the used test tubes.
When you are finished recording data, please clean up after yourselves. Wash the test tubes and put them face down in the racks. Throw away the excess dough and the used cups and spoons. Wipe off the counters and make sure you don't leave anything on the floor. Respect the classroom space, please.
Homework: Bring your laptops to class on Sunday. We will use Excel to create a table of your data, and then from the table, generate a line graph that shows time (X) versus dough height (Y). You should have at least five X values and five corresponding Y values. Your table should have a title and labeled axes. This will be included in your lab report. You will have to determine if your hypothesis was supported or refuted and provide an explanation.
Begin working on your lab report. The final report is due December 15. It is important to include all the elements of a lab report (you should know what they are by now), even safety precautions. If you want me to give you feedback, give it to me before then.