Photosynthesis and Respiration Lab
Biology BHS
(standards 1,3)
Pre-Lab Discussion
Oxygen and Carbon Dioxide play a significant role in the living process. In the Krebs cycle, chemical bonds in pyruvic acid are broken apart. Carbon dioxide molecules, ATP molecules, and hydrogen atoms are produced. Citric acid also is formed in the Krebs cycle. The citric acid is broken down and the cycle begins again. Carbon is released at all stages of the cycle in the form of carbon dioxide.
Cellular Respiration: C6H12O6 + O2 = 6CO2 + 6H2O + ATP Energy
Photosynthesis: Radiant Energy + 6CO2 + 6H2O = C6H12O6 + 6O2
All living things undergo respiration, which is the process whereby food molecules are broken down in the presence of oxygen. Humans and animals take oxygen and release carbon dioxide by breathing, which is easily observable. Plants do not “breathe” as humans and animals do, so respiration in plants is not easily observable. How do we know plants “breathe”?
Bromthymol Blue is a color indicator of the pH of an environment. It turns yellow in an acid environment, and it continues to maintain its blue color in an alkaline environment.
In this investigation you will be determining whether plants undergo respiration by releasing carbon dioxide. You will set up a closed system with Anacharis, Bromthymol blue indicator, and water. This system will be placed in two environments and observed for at least 4 days. You will be expected to write down anything you observe and report the observations in a formal lab write-up. Several questions appear at the end of this lab. Be sure to include the answers to these questions in the conclusion portion of your laboratory write-up.
Problem
Do plants perform respiration by releasing carbon dioxide in differing lighting environments?
Materials:
Micropipettes (4)
Pipette with 0.03% Bromthymol Blue Indicator
Anacharis
Water
96 well tray (2 per class)
Tape for labels
Straws
Razor blade
Procedure
1. Using the razor blade, cut off the end of the bulb on two of your pipettes as demonstrated by your instructor.
2. Fill the cut bulb with water 8-10 drops of 0.03% Bromthymol Blue and one leaf of Anacharis.
3. The cut bulb will be fitted on top of the bulb of an uncut pipette. Your instructor will demonstrate.
4. Label the straw holder with your lab group name and period.
5. Place the system into the 96 well tray.
6. Repeat steps 2-5 for your second system.
7. Be sure you know where your system is so that you can observe it for 4 days.
Your Data is expected to be in chart form like the example included in this guide.
EXAMPLE CHART
Key: *Color intensity and hue
*# bubbles and airspace (measure it)
Photosynthesis/Respiration Laboratory Data Chart (Figure 1)
Date/Day 0 / Date/Day 1 / Date/Day 2 / Date/Day 3Control #1
Dark
Control #2
Light
Pipette #1
Dark
Pipette #2
Light
This chart should include a (+) if there is any color change and a (-) if there is no color change. It should also include your daily observations about the experiment.
Answer the following questions to help you write a good conclusion and error analysis in your lab write-up.
Be sure to put the formulas for both cellular respiration and photosynthesis in your writeup. These two formulas will help you write a better report and answer the following questions.
1. Did you start with air in the pipette and was there observable change in the amount of air? If there was change in the amount of air as measured by a bubble, which pipettes and how much change occurred?
2. Compare the reaction that occurred in the pipette under the white light to the pipette kept inside the cupboard. Do this on a day by day comparison and use both any color change and air change in the pipettes.
3. How would your results have been affected if you had used more Bromthymol Blue or different concentration of indicator? Did you use the same amount of Bromthymol blue in each pipette? Did you make a note of the number of drops of bromthymol blue in the controls?
4. What is the function of the Anachris leaf in the system and how would your results been affected if you had used more than one Anacharis leaf?
5. What is the process of respiration and how is it common to all life forms?
6. Why do most living things take in oxygen based on your knowledge from your book or other references (cited)? Be careful and thorough in your answer.
7. Why is an understanding of glycolysis and the Kreb’s cycle important for the study of living things?
8. Explain the pipette(s) that contained everything except for the Anacharis?
9. Which of the tubes in the experiment contained color change if there was any color change? Be sure to address hue and instensity of hue and color change as compared to the original color.
10. If there was any color change, why did this occur?
11. Describe the daily environment of the pipettes.
12. What can you conclude about photosynthesis and respiration in relation to light energy?
13. Each lab partner is to include a way (different from each other) you would improve on
your experiment or do another experiment to test for photosynthesis or respiration.
LABORATORY WRITE-UP FORMAT
In completing your laboratory write-ups, be sure to utilize the following format. In addition, you are NOT to begin a lab UNTIL OR UNLESS YOU HAVE READ THE DIRECTIONS AND PROCEDURE THOROUGHLY! If the lab is one in which YOU are formulating the procedure, be sure that you have completed that part of your write-up PRIOR TO STARTING THE LAB!
Lab write-up format:
I. TITLE (An appropriate name for the experiment)
II. PURPOSE (Why you are doing the experiment; what you hope to accomplish)
III. MATERIALS/EQUIPMENT (List, identify, and diagram [if appropriate] the
materials, chemical reagents, and equipment you will
need to conduct your experiment)
IV. PROCEDURE (An outline, in your own words, of how you will conduct the lab)
V. OBSERVATIONS and DATA (What you see or need to record while going through
the experiment/procedure)
VI. RESULTS (any insights or information not included in your OBSERVATIONS and
DATA)
VII. CONCLUSION(s) (a discussion about what you learned/gained as a result of
conducting this experiment. Support your conclusion with your
data and observations)
VIII. ERROR ANALYSIS (How you and your lab partner might have made mistakes or
Introduced some degree of error in conducting your lab,
these would generally be things over which you had no
control!. See if you can come up with a minimum of three!)
To receive full credit for a:
FORMAL LAB WRITE-UP , you MUST include each of the above (#’s I-VIII).
INFORMAL LAB WRITE-UP, you MUST include #’s I, II, V, VII, and VIII. (You may omit MATERIALS/EQUIPMENT and PROCEDURE.
Agho bio photresplab
11/12/2008