As the students enter the room, they take out their journals and respond to the prompt: What is cellular respiration? If you are not sure, make an educated guess and provide evidence for your answer.
While the students work on the prompt, I circulate through the room reading through their answers. As I suspected, some of the students write information about breathing in their answer, because they associate the term respiration with breathing. Some of the students, as viewed in this example, think that cellular respiration has to do with cell reproduction/division.
After the students have had time to respond, I ask for volunteers to share their answers with the class. As each student responds, I ask the class if they agree with the answer and if anyone can supply more evidence to support the answer. This encourages the students to listen carefully to their classmates' answers and to think about support for their ideas.
After reviewing the students' journal responses, I tell the students they will be practicing taking notes from a text and I have the students access the online version of the cellular respiration worksheet. I also have copies printed out for students who prefer to hand write their notes. For this specific activity we use the 2000 edition of the Prentice Hall Science Explorer series. Information about cellular respiration written at the student level can also be found on the BBC's Bitesize website.
We review the key steps in taking notes while reading. For most of my class sections, I have the students use their textbooks to take notes. For some of the class sections, I read through the text with the students and have them fill in the information as we go paragraph by paragraph. For other sections of the course, I give the students fifteen minutes to work on their own and then we go over the information they filled in.
This note taking process addresses SP2 (Developing and Using Models) as students review visual models for cellular respiration and NGSS MS-LS1-7 as students review the manner in which cells produce energy through cellular respiration.
After reviewing the notes about cellular respiration and fermentation, the students turn in the notes they have written, either online or on paper. The students then take out their Chromebooks and enter the lab, where we work on the fermentation demonstration activity.
During this activity, the students work with a group to discuss the compounds and conditions that need to be present in order for fermentation to take place. We then work through the demonstration together. Each group receives a beaker and I place some yeast into their beaker. Next, they are asked to look and listen carefully to determine if fermentation is taking place. The students quickly realize that nothing is happening. This video demonstrates the way I check in with each group of students to ask them about their observations. Doing this holds the students accountable for staying on task and provides me with an accurate picture of what the students understand.
I then ask them to think back to the fermentation equation and what is listed on the reactant side. The students point out that glucose is needed for fermentation to take place. We have previously discussed in class that glucose is a sugar, so the students note that they need to add sugar to their yeast. I then give each group a small amount of sugar to add to their yeast and tell them again to watch carefully for signs of a chemical reaction.
Again, they are disappointed that nothing happens when they mix the sugar and yeast. I ask them if there is anything else we may be able to add to the yeast to cause fermentation to occur. They notice that I have been heating water in the front of the room, so some of the students realize that we need to add water to the yeast. I point out that yeast needs to be activated, so we use warm water. As a comparison, I also set up a beaker of yeast and water without sugar. Once the warm water is added, the students mix the items and notice that the odor of the yeast is much stronger than before. They also notice that the yeast mixed with the water/sugar solution begins producing very small bubbles.
Working on the fermentation activity addresses NGSS MS-PS1-2 as students look for evidence of chemical reactions and MS-LS1-1 as students look for evidence that yeast is a living organism.
I conclude the lesson by showing the students some yeast that has had more time to ferment. I then review with them the reactants and products of both respiration and fermentation. I expect the students to know that the reactants of respiration are glucose and oxygen while the products are carbon dioxide, ATP, and water, while yeast uses glucose as a reactant to produce ethanol and carbon dioxide.