Photosynthesis and Respiration Experiment Questions
questions to answer:
- What does CO2indicate in these tubes/cups? How did you measure the amount of CO2 produced?
- In which set up did you observe the maximum amount of respiration? Explain your answer.
- If we boiled the yeast, sugar and water mixture for 20 minutes and performed the same experiment, how much of CO2do you expect to be produced. Give explanation for your answer
- Is light necessary in photosynthesis? __________________________________________
Briefly describe the two reactions of photosynthesis and explain their dependence on light:
- Explain your conclusion about the occurrence of photosynthesis in setup 1.
- Explain your conclusion about the occurrence of photosynthesis in setup 2.
- What would happen to the life on earth if all processes of photosynthesis stop?
- Use colored pencils to draw your chromatography paper results and label the pigments. Upload a picture of your drawing here.
- The main pigments colors you observed in the leaves are ______________________________
What are their names? ______________________________________________________
Experimentation Online- Photosynthesis and Respiration
PART I- CELLULAR RESPIRATION
Yeast are single-celled fungi. The species called Saccharomyces cerevisiae is commonly called Baker’s or Brewer’s yeast. Like other eukaryotes with mitochondria, yeast can use oxygen to generate ATP in the process of oxidative phosphorylation. These yeast are facultative aerobes which means they can also switch to an anaerobic mechanism of ATP production called fermentation. In all organisms, the process of glycolysis occurs anaerobically in the cytoplasm to produce two pyruvate molecules from a single glucose. This process produces 2 new ATP molecules and reduced nicotinamide adenine dinucleotide (NADH).
Fermentation is an anaerobic process that occurs in the cytoplasm and quickly generates an additional ATP through the reduction of pyruvate. NADH is the source of electrons in this process that is oxidized to NAD+. Many organisms will ferment to generate lactic acid and CO2 from the pyruvate in order to generate ATP. Yeast fermentation produces ethanol and CO2. as byproducts.
In this experiment, we will use the amount of CO2 produced by a sample of yeast to measure the amount of fermentation. CO2 produced could be seen as bubbles in the reaction mixture.
3 tablespoons active dry yeast
3 teaspoons sugar
1/4 cup water
warm water in a big pan
Ice-cold water in a big pan
Transparent Disposable Cup
- Mix 1 tablespoon yeast and 1 teaspoon sugar with 1/4 cup water in three separate transparent disposable cups.
- Keep the first cup at room temperature, the second one in the pan containing ice-cold water and the third cup in a pan containing warm water.
- Record the amount of bubbles in all three cups at the start of the experiment or time zero.
- Record the amount of bubbles in all three cups after 30 minutes
- Answer questions in the Post-Lab Report.
PART II- PHOTOSYNTHESIS
Fresh or frozen spinach leaves
Alcohol (70% rubbing alcohol)
Acetone nail polish remover
Small glass jars with lid (sauce jar or baby food jar)
Lamp (blacklight /UV flashlight)
Coffee filter paper
- Observing photosynthesis and the necessity of light in the process
Enter this virtual lab (Links to an external site.) to study photosynthesis.
Lab setup 1: in the setting area, set “stop-at” at 2000, “Initial # of chloroplasts” at 3, “initial carbon dioxide” at 100, “water flow through leaf” at 25, “intensity of light” at 50, and check “auto-stop”.
Virtual lab setup 1 Virtual lab setup 2
Click on the “Setup/reset” button and record the initial numbers of the “carbon dioxide molecules”, “oxygen molecules”, and “sugar molecules produced” in section A of the lab report.
Click “go/pause” button to start the simulation. Observe the consumption of carbon dioxide and production of oxygen and sugar molecules in chloroplasts (green circles) during photosynthesis.
After the simulation stops, record the number molecules in the lab report (final number).
Now use lab setup2 to study the necessity of light. You can remove the light by directly typing “0” in the box of “intensity of light” or move the slider all the way to the left until it reads at 0.
Click on the “Setup/reset” button and record the initial numbers of the “carbon dioxide molecules”, “oxygen molecules”, and “sugar molecules produced” of setup 2 in the lab report.
Click “go/pause” button to start the simulation.
After the simulation stops, record the number molecules (final number of setup 2).
Complete related questions in the lab report.
- Extract chlorophyll and observe its fluorescence
When a leaf is exposed to light, its chlorophyll absorbs the light energy. This energy pushes the electron of chlorophyll into an excited state. The excited electron then transfers the energy from one molecule to another molecule in the thylakoid membrane to process photosynthesis. While in a situation where the light energy absorbed by chlorophyll cannot be pass on to perform photosynthesis, the electron will return to its original energy state, and in the process, release the light energy, and thus fluoresces. We will observe the fluorescence of chlorophyll in this experiment.
Use a scissor to cut five spinach leaves into very small pieces.
Place the leave pieces in a glass jar.
Add about 2 tablespoon of rubbing alcohol, soak the leaves pieces for 2 days or till the liquid is dark green.
Note: Alcohol is flammable – use it with care. As an organic solvent, alcohol dissociates the thylakoid membrane and dissolve the chlorophylls from the membrane.
Pour the liquid through a coffee filter paper and collect the extract to a small glass jar.
Turn off the room lights, shine a blacklight on to the extract and observe the color it fluoresce.
Complete section B of the lab report.
If you don’t have the materials, watch thevideo (Links to an external site.)here and complete section B of the lab report.
- Separate plant pigments by paper chromatography
Cut a strip of coffee filter paper long enough to stand in a glass jar as shown above.
Cut a point at the end of the paper.
Place a spinach leaf on the filter paper at the pointed end. Press and roll the edge of a coin over the leaf to crush the cells and form a stripe of pigment about 2 cm from the pointed end of the paper. Blow the stripe dry completely, and repeat this step at least 10 times at the same location on the filter paper until one dark concentrated stripe is created.
Note: use medium force to press the coin on the leaves to avoid breaking through the paper.
Add acetone nail polish remover to the glass jar for about 1 cm deep.
Note: Acetone is flammable – use it with care.
Slowly and carefully insert the filter paper with the pointed end towards the bottom in the jar with acetone solvent. Make sure that the dark stripe of plant extract is above the solvent.
Cap the jar and observe the solvent move up the paper until it comes within 1 cm from the top.
Remove the paper and immediately use a pencil to mark the position of the solvent.
Place the coffee filter paper on a paper towel to let it dry.
Observe your filter paper and locate the orange carotene at the top, followed by the yellow xanthophyll, the blue-green chlorophyll a, and the yellow-green chlorophyll b.
Draw a colored picture of your observation and upload the image to question No. 9 in the lab report. Also answer other relevant questions in the lab report.