8th Grade Lab Science (Cribb & Duane)
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Background:

Yeast are living things that are able to metabolize some foods, but not others. In order for an organism to make use of a potential source of food, it must be capable of transporting the food into its cells. It must also have the proper enzymes capable of breaking the food’s chemical bonds in a useful way. Sugars are vital to all living organisms. Yeast are capable of using some, but not all sugars as a food source.

Remember, that in order to survive, yeast must release the chemical energy of glucose through a chemical reaction.  This reaction is called cell respiration and occurs in all living things.  The equation for cell respiration (an exothermic chemical reaction) is as follows:

Glucose + oxygen -à carbon dioxide + water + energy

In this lab, you will try to determine whether yeast are capable of metabolizing a variety of sugars. When yeast carry out cell respiration, oxygen gas is consumed and carbon dioxide, CO2, is produced. You will use a CO2 Gas Sensor to monitor the production of carbon dioxide as yeast respire using different sugars.

The four sugars that will be tested are glucose (blood sugar), sucrose (table sugar), fructose (fruit sugar), and lactose (milk sugar).  Sugars and starches are types of carbohydrates that are a source of immediate energy to living things.  Glucose and fructose are examples of monosaccharides, while lactose and sucrose are types of disaccharides.  Starch, a polysaccharide, is not being tested in this lab experiment.

 

Figure 1

   

CLICK ON THE DIAGRAM FOR THE PROCEDURE

 

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Yeast Respiration of Sugars Lab Handouts:

Yeast Respiration Lab Handout

Yeast Respiration Experimental Design Worksheet

Yeast Respiration Blank Data Table

Yeast Respiration Lab Report Guidelines

Yeast Respiration Peer-Edit Checklist