This week we learn how cellular respiration releases energy in cells at the chemical, cellular, and body systems levels. We build on what we discovered about photosynthesis in Unit 1 to help students cement their recall of the gases involved. Middle schoolers often forget the word equations and concepts involved once they get to high school, so we approach these in multiple ways for long term recall. Skills learned include analytical reading, doing two inquiry labs, making a graph from a lab, connecting how lungs, blood, and muscles work together during exercise, and mastering vocabulary. Requirements for College Board standards include understanding how carbon and oxygen cycles through different organisms over historical time, which involves applying base ten mathematics to explain how dinosaur breath is likely in our lungs today.

Scroll down for materials and for standards that can be used for the Homeschool Audit documentation.

This fun activity is designed to show that cabbage juice turns from blue to red sooner after exercise than without exercise.  The directions are on the student page. 

Materials

One third red cabbage, bottled water, sieve, blender, teaspoon, two colorless drinking glasses or white cups, straws, timer/stopwatch, student able to exercise.

Activity

Hints for the activity: Stop the first bubbling as soon as the color goes pink. Save the first pink glass so there is an easy comparison with the second bubbling with exercise as to when to stop. Both resting and exercising will turn the color pink because cells at rest still do cellular respiration, therefore exercising may not turn the indicator pink faster even though in most cases it will.

The pink color is made by carbon dioxide turning the blue slightly basic cabbage juice indicator slightly acidic.

Students are invited to post to the group chat within Google Classroom to comment on where they think the extra carbon dioxide from exercise comes from. At this stage in the lesson set most students will not know the full answer though some will look it up. The main goal is to have students think about this at the cellular level as well as grasp that body systems: digestive system, muscle cells, blood circulation, and lungs all connect together to help us move.

Answers

What happened? The indicator went red from the carbon dioxide.

Did the amount of time change? Yes the exercise changed the red faster. 

Why or why not? Because the muscle cells needed more ATP and so they burned more glucose and released more carbon dioxide.

Which organelle in what cell type did the extra carbon dioxide come from? Muscle mitochondria.

If it "didn't work" do you think other cells in your body are also working hard and producing carbon dioxide? Yes, my brain cells are thinking, my muscles in my fingers are writing.

Don't forget to do student post in the Google Classroom chat stream.

This inquiry helps students identify that sugar as the source of cellular energy, rather than sweeteners or "energy" drinks with zero calories. Yeast is used as a model organism. In this case, yeast is performing fermentation as well as cellular respiration, producing both alcohol (fermentation) and carbon dioxide (cellular respiration). The sugary drinks should produce more bubbles and bigger balloons than the zero calorie drinks, low-cal "energy drinks," or water. 

The activity details are on the student page.

Graphing

Students are learning how to graph accurately, and it is important to take the time to do this well at this age. Students may confuse data tables with graphs: a graph has an x-axis and a y-axis. Data tables are numbers in columns, also known as spreadsheets.

Answers

Which "energy drinks" provide real energy for our cells? The higher calorie sugary drinks made more carbon dioxide.

What evidence supports your claim? We found the actual calories for each drink and measured yeast production of carbon dioxide to show these results. Yeast breaks down sugar to make carbon dioxide and water during cellular respiration and fermentation.

Use the graph to explain your thinking. The graph of bubble scores clearly show that drinks with more calories score higher than drinks with less, even if the drink tasted sweet from a sweetener such as stevia, and even if the drink was labeled an "energy drink." Energy drinks do not have real cell energy.

Materials

3 packets of Fleischmann's yeast (Rapid Rise). 

6 balloons to fit on the neck of water bottles or conical flasks.

6 empty recyclable water bottles or conical flasks.

6 non-bubbly drinks to compare: tap water, two sugary drinks (such as apple juice, mango juice), two zero-calorie sweetened drinks (such as Zevia, Diet Coke), and a sugar-free "energy drink." Save the bottles so we can read the food labels.

A basin of warm water that the drinks can sit in for an hour prior to the activity.