Cellular Respiration and Population Growth

In the first lesson, What Do Bread and Beer Have in Common?, students are introduced to yeast respiration through its role in the production of bread and alcoholic beverages. A discussion of the effects of alcohol on the human body is used both as an attention-getting device, and as a means to convey important information at an impressionable age. In the associated activity, Yeast Cells Respire, Too (But Not Like Me and You), students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures.

Based on questions that arise from the first activity, in the second lesson, Population Growth in Yeasts, students work in small groups as they design and execute their own experiments to determine how environmental factors affect yeast population growth. In the associated activity, How to Make Yeast Cells Thrive, students set up and run the experiments they designed using simple yeast-molasses cultures in test tubes. They test for a variety of environmental influences, such as temperature, food supply and pH.

Lessons and activities in this unit contain biomedical and chemical engineering topics such as biotechnology, applications of experimental and analytical techniques in living systems, food processing and processes of nature. Students also learn about the procedure used by engineers and scientists when designing experiments with controls.

• Day 1: What Do Bread and Beer Have in Common? lesson
• Day 2 and Day 6: Yeast Cells Respire, Too (But Not Like Me and You) activity (Note: 40-minute setup; ~5 minutes/day for observations for 3-4 days; 30 minutes for discussion and graphing results)
• Day 3: Population Growth in Yeasts lesson
• Day 4 and Day 8: How to Make Yeast Cells Thrive activity (Note: 30-minute setup; ~3 minutes/day for observations for 3-4 days; 30 minutes for discussion and graphing results)