Baking Bread - A real world application

It is important for our students to understand why we study the curriculum that we do, and where will it apply in their everyday lives, therefore, as a follow up to our lesson and lab on yeast respiration, we made bread. I pointed out that for centuries we humans have been taking advantage of the process of yeast respiration for our own benefit. Yeast are used in baking, cheese and yogurt production, and in fermenting wine and beer. The emphasis in talking about the process of bread baking was on the requirements for yeast growth (food source, warmth, darkness, and moisture) and how the recipe fullfills these. I also stressed that the bread rises because of the carbon dioxide which is being released as the yeast cells respire. In a previous lab, the students had studied what yeast need to live by "proofing" yeast. They had set up a beaker with yeast and water (the control), and a second beaker with yeast, water and sugar (the experimental sample). They then made a wet mount slide of each sample, staining the yeast in order to see them and count them. The samples were then left overnight in a warm, dark place. The following day the students again prepared wet mount slides of each sample and discovered that sugar caused an increase in the number of yeast cells.