Investigating Respiration (Holly Hawk)

Title: Investigating Respiration

Principle(s) Investigated: Cellular Respiration

Materials for breathing observation (per group): 1 beaker, 1 straw, 50 ml bromothymol blue, 1 freezer bag, 1 surgical tube, 1 rubber band

Materials for organism respiration observation: 6 test tubes, 6 barriers, 5 organisms to observe (one or two examples that will NOT respire), test tube rack, 5 ml bromothymol blue for each test tube

Standards: 9. As a result of the coordinated structures and functions of organ systems, the internal environment of the human body remains relatively stable (homeostatic) despite changes in the outside environment. As a basis for understanding this concept: a. Students know how the complementary activity of major body systems provides cells with oxygen and nutrients and removes toxic waste products such as carbon dioxide.

Procedure and Explanation: You must first make the bromothymol blue. You can buy bromo blue through a number of suppliers such as Fisher Scientific; it comes in a powder form.

Step 1. Fill Erlenmeyer flask with 500 ml Deionized water

Step 2. Measure out .1g bromo blue powder using a precise balance

Step 3. Mix bromo blue powder and DI water, the mixture will appear yellow.

Step 4. Place 1 drop .1M NaOH in bromo blue mixture and shake. Upon contact with NaOH, you will see a slight color change from yellow to blue. Continue this process until you observe the entire solution is blue.

You now have a fresh batch of Bromo blue! You will want to make this fresh the day before or the morning of your class experiment. If you let it sit for longer then 48hrs, you risk the experiment not working. Bromothymol blue is an acid base indicator… As your students breath into it, carbonic acid forms causing a color change due its acidity. The more obvious the color change, the more Co2 present. With different organisms, you should see different results of color change, which will be an indicator of rate of respiration.

Now you are ready to set up for your experiment and make your supplies. For the student breathing experiment, you simply need a freezer bag, surgical tubing and a sturdy rubber band. Seal the surgical tubing in to the freezer bag via the rubber band and voila! You have successfully prohibited your students from swallowing bromo blue… hopefully. They will use a straw (NOT the surgical tubing) to blow in to the bag, then seal the bag and expel the breath directly in to the bromo blue (approx 50 – 100ml in a beaker or flask) via the surgical tubing. If you want to demonstrate how exercise affects respiration, you can have some students do jumping jacks before breathing in to the bag and then compare their results to the students who were “at rest”.

For the observation of respiring organisms, you will fill the 6 test tubes with about ¾ of an inch of bromo blue. You will then place in each test tube a “barrier” so that the liquid at the bottom does not come in to contact with the organism you are to be observing. To make the barrier, take a bundle of slender coffee straws and cut them in to 2-inch segments. Then bundle them together, forming a circle, about as wide in diameter as the test tubes and place a strip of scotch tape around them. Slide barrier in to the bottom of the test tube until partially submerged in to the bromo blue. This will allow for the CO2 to mix with bromo blue but not touch the respiring organism. This is a good opportunity to demonstrate to students what is considered living and what is considered non-living.

Student Prior Knowledge: Students should have an understanding of cellular structure function, including organelles and the conversion of energy by organelles. Students should also have a basic understanding of photosynthesis; that although the byproduct of photosynthesis is O2, cellular respiration is still ongoing creating CO2 as well. It would be beneficial for the student to have an understanding of light reactions and the Calvin cycle, but this project could also be a starting point to explore these cycles. Students may also be more successful if they understand glycolysis and the citric acid cycle, but again, this experiment can serve as a jumping point for these cycles.

Questions and Answers:

1. How do organisms other than humans perform gas exchange?

Answer: Fish have gills (exception lungfish), where gas exchange takes place as O2 from water passes along the gill filaments. Insects do not have lungs, but have tracheal system used for gas exchange, where O2 enters through spiracles. Amphibians have lungs but also can exchange gas through the skin.

1. Will a plant continue to respire in the dark?

Answer: Yes, but not for an extended amount of time. The products of photosynthesis are what enter the Calvin cycle. Some energy storage will be available for a plant to draw upon in dark conditions (like a closet) but once the energy storage is used, the cells will not be able to respire and the plant will senesce. The time frame for senescence will be different for different species or even the same species but different plant due to differential energy expenditures.

1. How might your body react (in terms of respiration) if you spent the day at the top of Mount Whitney?

Answer: Less oxygen is available at higher altitudes, so one would expect rate of respiration to increase at higher altitudes so that adequate O2 is delivered to cells. One might expect shortness of breath or fatigue due to higher energy expenditures at high elevations.

Application to Everyday Life:

Exercise: If cells don’t have enough oxygen, the cells use lactic acid fermentation (a form of anaerobic respiration) to supplement O2 supplies. The lactic acid build up is what makes your muscles sore. Eventually, the lactic acid is transported by the blood to the liver. So if you feel sore the day after hitting the gym, you may want to take it easier on your muscles next time.