As teachers, we all have that one topic we hate to teach. For me, it’s photosynthesis and cellular respiration. They learn the basics in middle school: plants need water, carbon dioxide, and sunlight, and in turn they create oxygen and glucose. Then glucose gets broken down and turns into energy. End of story.
In college or AP biology, students have to learn the nitty gritty of glycolysis, krebs cycle, and electron transport chain. The biochemistry can make your eyes glaze over. It has always been a struggle for me to figure out what exactly to cover for the average high school student. What is that “happy medium” I can cover that will give them more than the basic formula, but not so much they get overwhelmed?
I’ve decided that that happy medium looks like this:
Students need to memorize the overall formula for cellular respiration. They should recognize the products for photosynthesis are the reactants for cellular respiration and vice versa.
Students should understand the inputs and outputs of glycolysis, the krebs cycle, and electron transport chain, but don’t need to understand all the biochemical reactions.
Students should be able to apply cellular respiration concepts to real world situations. How is cellular respiration utilized in cooking? Why do Olympic athletes train at high altitudes? What impact does temperature have on respiration and how does this apply to cold blooded organisms? (Notice now none of these questions involve students explaining what Acetyl-CoA is or how electron transport works?)
Here is a round-up of what I consider “happy-medium” respiration lessons.
1. When I introduce the topic of cellular respiration, I usually use bromothymol blue as a demo. Fill a beaker with roughly 150mL of water and 2mL of bromothymol blue. Discuss with students that bromothymol blue is a pH indicator and will change from blue to green as the solution becomes more acidic.
Call up a volunteer to blow through a straw into the beaker. Time how long it takes to change from blue to green. Then repeat the experiment, but before allowing them to blow into the straw, have the student do some jumping jacks, pushups, or something to get their heart going. Ask the class- do you think it will take more time or less time for the color to change from blue to green? Why?
2. If you have access to some aquatic plants and bromothymol blue, this carbon cycle lab is fun with easy set-up. Students place some aquatic plants (elodea works great, but any aquatic plant will work) in test tubes and fill with water and bromothymol blue, which is a pH indicator. Placed in the light, the plants will produce oxygen and students will see the color change from green to blue in one test tube. If the test tubes are wrapped in tin foil to block any light, the plants will only do respiration and the color will change from blue to green in one vial. If you’d like to read more about how I set up this lab, head to this blog post.
3. Here is a free “barf bag” activity from Suburban Science. Students mix cereal, yeast, and water in a ziploc bag and observe the accumulation of carbon dioxide in the bag.
4. Similarly, here is a “sourdough starter” respiration activity. This is a great tie-in with food science!
5. Speaking of food science, this lab has students make root beer while learning about cellular respiration.
6. This interactive diagram has clickable slides for both photosynthesis and cellular respiration. Students can click on each step and learn about what occurs, as well as watch video clips and try out some interactive websites. Also included is a google form self-grading quiz students can take following the activity. You can find it on my website or on Tpt.
7. Do you have access to probeware? If so, you can have students measure the rate of respiration in different organisms. You can purchase crickets inexpensively and have students measure the respiration rate in a cold water bath vs warm water bath. If you would prefer to not use invertebrates you can use germinated peas or beans. Here is a lab worksheet you can use.
8. This station activity was created with the intent to give students an opportunity tounderstand and apply big picture respiration concepts, not memorize biochemistry steps. Stations include things like observing yeast cells undergoing respiration, reading about the 1980’s Tylenol killer, and comparing the respiration rate of crickets in warm and cold temperatures. High interest and low prep! You can find it in my TpT store here or on my website.
9. In this virtual lab activity from Biology Corner, students measure the impact of temperature on the rate of respiration in a goldfish.
10. Here is another virtual lab activity you might want to check out that uses yeast.
11. If you want something students can glue into an interactive notebook, you might be interested in this respiration flip book. Students cut out the 6 flaps, staple them together, and identify the major components of glycolysis, krebs cycle, and electron transport chain. You can find it on my website or on TpT.