Standard III: Students will understand the structure of cells and organisms.
Objective 1: Observe and describe cellular structures and functions.
Indicator e: Describe that many of the basic functions of organisms are carried out within cells (e.g., extract energy from food, remove waste).
Intended Learning Outcomes:
1 D. Select the appropriate instrument; measure, calculate and record in metric units, length, volume, temperature and weight, to the accuracy of instruments used.
1 E. When given a problem, plan and conduct experiments in which they:
› Form research questions and hypotheses.
› Predict results of investigations based upon prior data.
› Identify variables.
› Plan procedures to control independent variable(s).
› Collect data on the dependent variable(s).
› Select appropriate format (e.g., graph, chart, diagram) to summarize data obtained.
› Analyze data and construct reasonable conclusions.
› Prepare written and oral reports of their investigation.
3 A. Provide relevant data to support their inferences and conclusions.
4 B. Use precise scientific language in oral and written communication.
4 C. Solve problems appropriate to grade level by applying scientific principles and procedures.

Background: Students should have general knowledge of the functions of organelles within the cell. They should understand that yeast extracts the energy in sugar and produces Carbon dioxide (CO2) waste.

Time Required: 45 minutes

Summary: Have you ever baked bread? What is it that makes the bread rise? It’s the yeast. But what is it that makes the yeast grow? It’s the sugar. Yeast extracts the energy from the sugar to make it grow. In the process, it produces Carbon dioxide waste. It is the Carbon dioxide waste that makes the bread rise or have holes in it.

Materials List:

• Heat source
  
• Balance
  
• weighing paper
  
• Beaker (to heat water)
  
• Thermometer
  
• String
  
• scissors
  
• Metric Ruler
  
• Ziploc Sandwich Bag
  
• 2 g. yeast (room temperature)
  
• 10 g. sugar
  
• 50 mL warm (38 degrees Celsius) water
  
• 50 mL graduated cylinder
  
• Stop watch or clock
  

Safety concerns:

• Be sure to keep all chemical, heat, and glassware safety rules that are specified by your teacher and in all general laboratory experiences. Do not eat the yeast. Remember not to put a stopper into any flask unless given direct instruction by your teacher.

Procedures:

1. heat water to 38 degrees Celsius
   
2. measure 2 g. yeast and place in ziploc bag
   
3. measure 10 g. sugar and place in ziploc bag
   
4. measure 50 mL water and place in ziploc bag
   
5. mix yeast, water and sugar with fingers in bottom of ziploc
   
6. push air out of ziploc bag an seal
   
7. roll ziploc from top down and measure thickness of ziploc
   
8. start stopwatch at zero
   
9. record measurement
   
10. continue mixing yeast in bag with fingers
    
11. record measurement of bag every 5 minutes

Sample Data Table:

Time (Minutes)	Size (cm)
0	10.5
10	11
20	12
30	13
40	14

Sample Graph

Visit the Utah State 7th Grade Integrated Science Core Curriculum Page.
Updated August 27, 2001 by: Glen Westbroek

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