Science as a way of knowing requires the formulation and testing of hypotheses. Hypotheses are tested via objective observations. In this laboratory exercise, you will be testing a hypothesis about cellular respiration in germinating versus dormant beans.
During cellular respiration, the energy stored in the chemical bonds of glucose is released to produce energy in the form of ATP. ATP can be used to power cellular activities, such as helping to build new cellular structures like plant shoots and leaves. Cellular respiration occurs in the mitochondria of both plant and animal cells.
The chemical equation of cellular respiration is:
C6H12O6 + O2 ---> CO2 + H20 (Some ATP is also produced).
Glucose + Oxygen ---> Carbon dioxide + Water
You will study rates of respiration by measuring carbon dioxide production in germinating and dormant beans using an indicator solution called bromothymol blue. This indicator solution turns more of a brownish-yellow color under acidic conditions. Carbon dioxide reacts with water present in bromothymol blue to produce carbonic acid, an acidic condition.
A well designed experiment includes controls. Controls indicate that the experimental groups are treated identically except for the condition being assessed. Measurements collected from tests of hypotheses are called data. The data you will be collecting will involve noting color changes.
Procedure - Use the materials in the Unit 1 bag of your lab kit.
- 1.Place 25 kidney beans in one beaker.
- 2.Add water to the beans, bringing the total volume in the beaker to 100mL
- 3.Take a dated photo showing your beans in water. Submit this photo to the proper assignment on Moodle showing you completes this by the required time. Undated and 4.late photos receive zero points.
- 5.Allow the beans to soak in the water for ~ 48 hours. This will begin the germination process.
- 6.After the 48 hour incubation, empty the water from the beaker and temporarily remove the soaked germinating beans.
- 7.Fold each of the three paper towels several times.
- 8.Moisten all three folded paper towels and place one at the bottom of each of three beakers. The paper toweling should be on the bottom of the beakers and not up the sides too far.
- 9.Place 25 germinating kidney beans into one beaker, 25 dormant kidney beans into a second beaker and zero beans in the third beaker.
- 10.Add 5ml of bromothymol blue solution to each of the three small medicine cups, and place one medicine cup inside each beaker.
- Watch the Parafilm application demonstration.then stretch the Parafilm tightly across the top of each beaker to create an airtight seal.
11. Use Microsoft word to make a table with 4 columns and 5 rows. Label the four columns Time, Germinating Beans, Dormant Beans and No Beans. The 5 rows will include Time from the first column and 0 mins, 1 hour, 2 hours, and 3 hours. If these times do not work for your work and class schedule, you can modify them slightly, but discuss drastic modifications with me and record the actual times you use in your table.
12. Record bromothymol blue color changes at the times listed in the table.
13. Take a dated photo showing your beakers at the 3 hour time point. Make sure the medicine cups are visible in the photo.
14. Take another dated photo showing your completed table.
15. Dry the beakers and place in the Unit 2 supply bag, along with the lab tape and Sharpie.
question to answer:
1. (15 points) Summarize in one or two paragraphs how the design of this experiment helped us understand cellular respiration. In other words, why was this experiment carried out the way it was; what did the controls tell us; what does a color change in bromothymol blue mean; why did we keep the beaker covered in parafilm; etc. Only well written, thoughtful answers will receive credit so take your time and think through all the variables and what they mean. Ask Professor Belk for help if you need it.
2. (15 points) Summarize in one or two sentences what the results of this experiment showed about rates of germination in the germinating and nongerminating beans. Do these results make sense? Why or why not?