Growing Yeast Activity

1. Growing Yeast Activity

2. Prior Knowledge: • In grade 5, you learned about the structure and function of the major organs in the major body systems. You also explored how the skeletal, muscular, and nervous systems work together. • In previous years you have also explored the characteristics of life, as well as identifying variables, observation skills, recording data, and precise use of vocabulary.

3. Did You Know? • Living cells require oxygen and nutrients (food) and produce waste products. This is true of unicellular organisms such as yeast and multi-cellular organisms such as humans. 

4. Did You Know? • Yeasts are unicellular fungi. There are yeasts living in a wide variety of natural habitats. For example they live on plant leaves, flowers, soil, water, and skin surfaces. The yeast used in baking and alcohol fermentation is usually a strain of Saccharomycescerevisiae.

5. Yeast cells require both food (a source of nutrients) and water for survival, reproduction and growth. The growth of yeast is also influenced by the pH and temperature of the environment. The presence or absence of oxygen and the presence of metabolic products that they make through fermentation (acids or alcohol) will also affect yeast growth.

6. When yeast metabolizes sugar one of the waste products is carbon dioxide gas. In an anaerobic (without oxygen) environment, it also produces ethanol (alcohol) as a waste product.

7. As unicellular organisms are in direct contact with their environment they can absorb nutrients and release waste products directly to the environment. However, most cells of multi-celled organisms are isolated from the environment and so receive nutrients and release waste through systems with specialized functions (e.g. circulatory, digestive, and excretory).

8. Each system of the human body groups organs that work together. Each organ is made up of two or more different kinds of tissue, and each type of tissue is made up of similar cells working together.

9. Has anyone made bread from scratch? • An important step of making bread is letting the dough “rise”. • What ingredient makes the dough “rise”? (Yeast) • What is yeast? • Is yeast alive? • What do you know about yeast?”

10. Place Mat Activity • Fold a sheet of paper is into four sections diagonally. • In groups of four, each student has a separate section in which to write what they know about yeast.

11. pH • pH is a measure of the acidity or basicity of a solution. • Pure water is said to be neutral. The pH for pure water at 25 °C (77 °F) is close to 7.0. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are said to be basic or alkaline.

12. In this activity, you will grow yeast. • The first step is to prepare your lab write-up. • Be sure to include: Title Hypothesis Apparatus/Materials Procedure Observation Conclusion

13. Introduction • In this lab you will be using 2 water bottles. In each bottle you will be placing a spoonful of yeast, a spoonful of sugar and a scoop of water. A balloon will be used to seal the mouth of each bottle. • Make a Hypothesis about what you think will happen.

14. Materials • Yeast • Sugar • Water • 2 containers per group (plastic water bottle) • Balloons or Ziploc baggies • Masking tape • Marker • Timing device • Spoons of various sizes

15. Procedure • Using the 2 water bottles provided, in each bottle: • Place 1 spoonful of yeast • Add 1 spoonful of sugar • Pour 1 scoop of water (some groups will get warm water and some will get cool water.) • Place the balloon over the mouth of each bottle and observe for 5 minutes • What do you notice? • Are both of your bottles the same? • Look at results from other groups. Which group has completely different results from what you found? Talk to them to see what they did differently.

16. Observations • Make observations on what is happening inside the bottle. • Discuss with you table partners how to measure and record your observations. • Did you notice if the two bottles have similar results? • Compare your results to those of other groups.

17. Reflection: In small groups • In your group discuss: • What did you notice? • Rotate around room to look at other results. • Find the group with results most unlike yours and talk with that group to figure out what they did differently. Make a note of your findings at the end of you Lab Report under the heading: Reflection

18. Reflection: Class Discussion • What factors may have contributed to the variety of results?

19. Possible Factors • amount of yeast, sugar, water • temperature of the water, temperature of the room – especially if they were left overnight • How fast the balloon was put on or the baggie sealed, if there was a tight seal between the neck of the bottle and the balloon or the baggie

20. Questions to Consider • What is happening to the sugar? • Why does the balloon or bag inflate? • Look at list of facts about yeast that we completed last class. Are there any items that should be added to or revised? Is there other information we could add?

21. Reflection: Journaling • In your notebook create a journal entry, describe the variability in experimental results observed in yourclassroom. Suggest reasons for the variability.

22. Part II

23. Factors That Affect Yeast Activity • From the last activity you learned that yeast needs food (sugar) and water. • Based on the similarities and differences between the experiments done earlier, you will design and carry out some experiments to see what has an effect on yeast growth.

24. Next you are going to design your own experiments. • Be sure that you are only changing one variable at a time. Check with the teacher before completing the experiment. • You will use a rubric to assess your work, it will be provided for you.

25. Rubric Breakdown

26. Materials • Ziploc bags or containers (water bottles) and balloons • Liquids such as water, apple juice, and/or pop (Root Beer and Orange Soda) • Salt, sugar • Ice, hot water • Teaspoons, tablespoons,measuring spoons, measuring cups • Yeast • Pepper • Corn Starch • Baking Soda • Vinegar

27. What to do • In small groups write a question concerning the growth of yeast that you could test. • You should outline your procedure with projected amounts, how you will make measurements and record them, and/or time and make a prediction that reinforces your choice of variable.

28. Try it out • Perform your experiments using the procedures you created earlier. • Record your results paying close attention to the measurements you used and the observations you made. • Check to see what other groups are testing if you are struggling to design an experiment.

29. Some Ideas to Help • Possible experiments may include altering the amount of sugar such as doubling or halving; adding salt; using different liquids such as juice, Five Alive, vinegar; adding carbon dioxide by blowing into the container with a straw; using hot water; or ice water; adding food colouring...

30. You should write up your question, materials and procedure to hand in.

31. Reflection: Class Discussion • Share your results with the class and what that tells us about yeast. • What factors seemed to make the yeast produce the most gas? The least? • Explain why these factors affect yeast the way they do.