Fermentation+Lab

Instructions:
Read through the //entire// lab and answer the prelab questions at the end BEFORE coming to class.

For a downloadable version of the lab click here

** Fermentation by Yeast ** All living organisms need energy – energy to move, energy to grow and repair damage, energy to reproduce, energy to maintain homeostasis. //Producers// – plants, some bacteria and algae – are able to trap energy from sunlight and store it in the form of “food” during the process of //photosynthesis//. //Consumers//, like us, have to get food from their environment. But whether you are a producer or a consumer, living organisms must break down food to get the stored energy out of it.
 * // Introduction //**

Food must be broken down into a useable form – the molecule **ATP.** This can be accomplished in two ways.


 * 1) __ When O2 is available __, cells use **cellular respiration** to convert the energy in food to ATP. Cellular respiration is essentially the reverse of photosynthesis. Cellular respiration can make up to 38 molecules of ATP per molecule of glucose. Cellular respiration takes place in mitochondria.
 * 2) __ When O2 is not available __, cells can make ATP using a process called **fermentation**. Fermentation produces only 2 molecules of ATP per molecule of glucose. Fermentation does NOT happen in mitochondria. It happens in the cytoplasm.

There are two types of fermentation:
 * ** Lactic acid ** **fermentation** produces lactic acid. (e.g. in muscles when an animal exercises hard)
 * ** Alcoholic fermentation ** produces CO2. (e.g. in yeast, which can be used to make wine or beer) This is what makes bread rise.

In this lab we will observe fermentation in yeast cells. Yeast are single-celled fungi.

To measure the rate of fermentation in yeast, you can measure the amount of CO2 gas the yeast produces. By trapping the CO2 gas in a balloon, you can measure the amount by measuring the circumference of the balloon.

To observe the effect of sugar concentration on the rate of fermentation in yeast.
 * // Purpose //**


 * // Materials (per group of 4) //**
 * 5 125ml Erlenmeyer flasks
 * 5 balloons
 * Masking tape
 * String & Ruler for measuring balloon circumference
 * 5 Dixie cups
 * 12.5g bakers yeast, divided into five 2.5g portions (in Dixie cups)
 * 15g Sugar
 * 500ml Warm Water
 * Stop watch


 * // Procedure: //**
 * 1) Label your flasks 1, 2, 3, 4 and 5 with masking tape.
 * 2) Pour one 2.5g portion of yeast into each flask.
 * 3) Using your empty Dixie cups, weigh the sugar according to the amounts listed in the data table: 1.0g for flask 2, 2.0g for flask 3, and so on. (Remember flask 1 gets no sugar).
 * 4) Pour sugar into the appropriate flask.
 * 5) Inflate each of your balloons and then let the air out. This stretches them out so they can inflate more easily later.
 * 6) Add warm 100 ml water to each flask.
 * 7) Stretch the mouth of a balloon over the mouth of each of your flasks. Secure the balloon with masking tape.
 * 8) After 10 minutes, measure the circumference of each balloon using your string and ruler combo (I’ll show you how). Record the circumference in a properly labeled data table.
 * 9) Repeat step 8 after 20 and 30 and 40 minutes have elapsed from the **//start//** of the experiment. Record in your data table. (While you’re waiting you can calculate the volume of each balloon.)
 * 10) Once you’ve collected all your data, remove the masking tape and balloons, and rinse out your flasks. Put all materials back on the table they way you found them, and clean up any spills at your desk.
 * 11) Finish calculations, and start working on the analysis questions and conclusion.


 * Example Data Table: ** Use this table as a guide, but record all of your data in tables that you’ve drawn in your journal.

** Effect of Sugar Concentration on Fermentation Rate **

at 0 min. (cm) ||  Vol. at 0 min (cm 3 )  ||  Circ. at 10 min. (cm) ||   Vol. at 10 min. (cm 3 )   ||  Circ. at 20 min. (cm) ||   Vol. at 20 min (cm 3 )   ||  Circ. at 30 min. (cm) ||   Vol. at 30 min. (cm 3 )   ||  Circ. at 40 min. (cm) ||   Vol. at 40 min. (cm 3 )   ||
 * Flask ||  Mass Sugar (g)  ||  Circ.
 * 1 ||  0  ||   ||   ||   ||   ||   ||   ||   ||   ||   ||   ||
 * 2 ||  1.0  ||   ||   ||   ||   ||   ||   ||   ||   ||   ||   ||
 * 3 ||  2.0  ||   ||   ||   ||   ||   ||   ||   ||   ||   ||   ||
 * 4 ||  4.0  ||   ||   ||   ||   ||   ||   ||   ||   ||   ||   ||
 * 5 ||  8.0  ||   ||   ||   ||   ||   ||   ||   ||   ||   ||   ||

Use this formula to calculate the volume of CO2 gas your yeast produced in each flask for each time point:
 * // Calculating Volume of CO2 Gas: //**

** Volume = __Circumference3__ ** ** 6 **** Л **** 2 **

Record the volume of gas produced for each flask in your data table.


 * // Prelab Questions: //**** Answer each of the following questions in your journal. Answer with complete sentences. **
 * 1) What is cellular respiration? Why is it important?
 * 2) What is fermentation? What kinds of cells do fermentation?
 * 3) Which process produces more ATP: cellular respiration or fermentation?
 * 4) What is yeast? What kind of fermentation do yeast carry out? What is the main bi-product of this type of fermentation?
 * 5) How will we __observe__ the process of fermentation in this lab?
 * 6) Make a __diagram__ of the procedure (draw and label the contents of the five flasks)
 * 7) Copy the data table into your Science Journal.


 * Analysis Questions: **
 * 1) Did the amounts of CO2 produced at different sucrose concentrations match your predictions? If not, how did the results differ from your expectations?
 * 2) What conclusions concerning the relationship between sucrose concentration and the rate of alcoholic fermentation are supported by your results?
 * 3) Compare your results with the class results or with the results of the group next to you. Are your results generally similar? If there are any significant differences in results, what could be the reason for these differences?
 * 4) When you make bread, if you just mix flour, sugar and water, the dough does not rise, and the bread will be flat and hard. If you include yeast in the bread dough, then the dough rises and the bread is bigger and fluffier.
 * Explain how yeast helps the bread dough to rise.
 * Consider the results of your last experiment with yeast and sucrose. If you added flour, which treatment would have made the fluffiest bread?