Derak-Photosynthesis Lab Report Rough Draft

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Makayla Derak Lab section 12 October 25, 2022 Photosynthesis Lab Report Introduction Photosynthesis is a fundamental process, which is vital to sustain life on our planet. Why is it that photosynthesis is compulsory to our existence? In simple terms, photosynthesis is a process by which plants and other select organisms transform sunlight, carbon dioxide (CO ₂ ), and water (H ₂ O) into a chemical energy, resulting in the production of the sugar glucose, and oxygen (Bassham & Lambers, 1998) . Photosynthesis was partially discovered in the late 1700’s by a Dutch chemist, biologist, and physician named Jan Ingenhousz when he conducted an experiment comparing plants fully placed in sunlight versus shade. This led to the realizations that plants produce oxygen, and light is essential for photosynthetic processes to occur (N.A., 2019) . An American scientist named Charles Barnes later added to this discovery by proposing and coining the terms photosynthesis and photosyntax for the process in which there was a combination of complex carbon compounds out of carbonic acid, there was a presence of chlorophyll, and was directly affected by light energy (Gest, 2002) . The more frequently used term, photosynthesis is derived from the greek words Phōs, meaning light and σύνθεσις, meaning combining together. These two words come together meaning the term photosynthesis is referring to building with the assistance of light (Merriam Webster, n.d.) . We know a large amount about photosynthesis, but we still have areas yet to be researched. The process of photosynthesi s occurs when plants use sunlight to create energy, however, scientists are currently exploring options of photosynthesis using artificial light. Scientists envision this to convert sunlight into chemical fuels for an unlimited and sustainable energy source (RES, 2022) .

Photosynthesis may seem to be a simple procedure, however, it is a very complex process with many subcomponents, and is an area of ongoing research. The balanced equation for photosynthesis is 6CO2+6H2O→C6H12O6+6O2 (carbon dioxide, water, and light produce glucose and oxygen) (Newton, 2019) . This process begins in the thylakoid membrane when plants use pigment molecules which are chemical compounds that absorb certain colors of light energy, while reflecting other wavelengths of visible light. The most common and known pigment source in the photosynthesis process is chlorophyll. Chlorophyll appears as a green color, which indicates the absorption of red and blue waves, but the reflection of green wavelengths. This results in the perception of a green pigment in many plant species. Although the most recognized pigment, chlorophyll, is not the only pigment in the process of photosynthesis. The three basic classes of pigments consist of chlorophylls, carotenoids, and phycobilins, each with subunits and their own individual functions in the instance of light absorption and reflection (Khan Academy, 2015) . There are two stages of photosynthesis; the light dependent reactions and the light independent also called the calvin cycle. The light dependent reactions occur in the thylakoids membranes of the chloroplasts where photosystem II begins when the chlorophyll pigment gathers light energy from the sun (photons) and begins the breakdown process of water molecules. These photons are used to remove electrons from the water molecules and are then sent through the electron transport chain. This process results with the production of ATP, NADPH, and O ₂ (Oxygen) by photosystem I which are used in the next cycle; the independent reaction (Peterson & Rapini, 2021) . This reaction occurs in the stroma within the chloroplast. At this point in time the chemical energy harvested in the light dependent process is now used in the

light independent process to transfer carbon dioxide into the production of glucose. To begin this process carbon dioxide is first drawn in through stomata which is a fluid within the inner space of the chloroplasts. The CO ₂ molecule then reacts with RuBP which is catalyzed resulting in 3-PGA at which point the reaction is catalyzed by the Rubisco enzyme . This subunit is referred to as CO ₂ fixation. The next subunit in the light independent process is reduction. In this stage ATP and NADPH molecules transform the 3-PGA from the fixation stage into the three-carbon sugar, G3P. This transformation occurred from the donation of electrons from NADPH. The third and final subunit in the light independent phase is regeneration. In the regeneration stage a number of G3P molecules are used to produce glucose, but not all. Some G3P molecules need to be recycled in order to replenish the RuBP acceptor. The carbohydrate molecule has six carbon atoms, meaning it takes 6 cycles to create one molecule of the glucose sugar (Khan Academy, 2015) . Methods With this information we were able to recognize the processes taking place in our own photosynthesis experiment. The initial part of this was to determine the respiration rate. To do this we first connected the Vernier Lab Pro software to the computer and attached the O ₂ gas sensor. The Logger 3 Pro software was then opened as well as the Oxygen Gas Sensor folder. Next we set the duration to 10 minutes and set the software to 20 samples per minute. In this step it was important to ensure the units were set to ppm. Our next step was to obtain a respiration chamber and we fully encased it with aluminum foil to ensure light was restricted. A spinach leaf was acquired and weighed immediately. The spinach was gently placed down flat in the respiration chamber on a wet piece of paper towel, facing perpendicularly to the light source. The wet paper towel was needed to prevent inaccuracies in our experiment due to our leaf

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becoming dehydrated. Avoiding direct interaction between the respiration chamber and lamp, the bottom of the bulb or the rim of the lamp shade was moved 7cm from the table. We ensured the light was as close to 90° to the respiration chamber as possible. Next we placed the O ₂ Gas Sensor tightly into the chamber and laid it on its side under the fluorescent light. A timer was set for 5 minutes to allow time for acclimation. After 5 minutes elapsed we pressed the collect button on the Logger Pro software and gathered our measurement of the O ₂ concentration for 10 minutes. After this, we were able to determine the rate of respiration. To do this we clicked the Autoscale graph button on our software’s toolbar, the cursor was moved to the beginning of the data values, and the region of decreasing oxygen gas concentration was selected. To perform a linear regression we pressed the linear fit button, and the slope of the line was recorded. In the experiment menu we chose the store latest run to save our data. Without removing the O ₂ sensor from the chamber, the aluminum foil around the respiration chamber was removed and saved for the next trial. Our second goal in this experiment was to determine photosynthesis (net) rate under light. In this section of the experiment we began with repositiioning the chamber under the light, the O ₂ sensor still within the chamber. Again, we waited 5 minutes before beginning our data collection. We used the Logger Pro software to collect and store our data as we did previously. The spinach was then removed from the respiration chamber and the O ₂ sensor was flushed by waving a notebook in front of the sensor for approximately a minute. Our next step was to clean and dry our used respiration chamber and repeat these procedures again with a new leaf. Results I hypothesized that the red and blue light colors would be the better drivers in this experiment as they are the most absorbed colors. In our group, the light color red was used to

conduct this experiment. In total, the class tested 2 red light colors, 2 white light colors, and 1 blue light color. First we measured the weight of our first leaf. We concluded that our leaf in particular weighed 0.9729g. In comparison the other group using red light had a weight of 1.481g for their initial leaf. We measured the Dark O ₂ consumption to be -39.82 ppm/m and the other group calculated theirs to be -89.28ppm/m. Still using the unit ppm/m we measured our light O ₂ product To be 91.36 and the number 136.8 was measured for the group also using the red color. Next we calculated the gross photosynthesis rate of both the light and dark reactions and received the number 51.54 ppm/m. The other group calculated theirs to be 47.52ppm/m. Our final calculation for our first leaf was the gross rate by mass. Our number was 52.97ppm/m compared to 32.1ppm/m for the alternative group using red light. We repeated these calculations twice more with different leaves. The start weight of our second leaf was 0.8235g and 1.596 for our third. The second group using the red color weighed their second leaf at 1.557g and the third at 1.746g initially. The dark O ₂ consumption was measured at -21.99ppm/m for the second leaf and the third at -26.62ppm/m compared to -37.34ppm/m and 42.43ppm/m. We received light O ₂ production in ppm/m numbers of 82.79 and 137.22 and 1124.1 and 126.1 for the other group. The gross photosynthesis rate was calculated at 60.8ppm/m for our second leaf trial and 110.6ppm/m for our third. The other group calculated their second leaf at 86.86ppm/m and 83.67ppm/m for their third. Groups testing other colors also recorded these 5 categories for 3 trials. There were 2 groups using the white light so they will be referred to as group A and group B. Group A calculated their leaf weights to be 1.05g, 1.26g, and 1.04g. Group B calculated their weights to be 1.377g, 1.574g, and 1.483g. The dark O ₂ consumption was recorded as 90.68ppm/m, and the third trial was left unfinished for group A. For group B, the dark O ₂ consumption was recorded as 7.306ppm/m, 19.54ppm/m, with the third trial being unfinished as

well. Using the ppm/m units, the light O ₂ production of the first group, group A, recorded their first leaf to be 152.8 and their second at 129.1, again, the third trial was unfinished. For group B numbers were recorded as 130.0, and 155.2 with the third trial unfinished. For both of these groups the third trial is unfinished for the remainder of categories. The next category was the gross photosynthesis rate of both the light and dark in ppm/m. Group A received the numbers 243.5ppm/m and 140.2ppm/m. Group B received the numbers 137.3ppm/m and 174.7ppm/m. The final category was gross rate by mass which Group A calculated to be 231.9ppm/m and 111.3ppm/m whereas Group B calculated their numbers to be 99.71ppm/m, and 111.0ppm/m. The individual group using blue light weighed their leaves at 1.3058g, 0.8370g, and 1.2536g. The numbers for the dark O ₂ consumption were -108.5ppm/m, -33.88ppm/m, and -12.46ppm/m. Light O ₂ production numbers were 163.5ppm/m, 166.5ppm/5, with the third trial remaining unfinished from this point forth. The gross photosynthesis rates were 55.0ppm/m for the first trial and 131.6ppm/m for the second. Lastly, the gross rate by mass for the blue light was calculated at 42.0ppm/m and 157.3ppm/m. In Dark O ₂ consumption red and blue light both appear to commonly be negative numbers. White light seems to consistently produce positive numbers in each category. The red light data shows the lowest gross rate by mass.

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Discussion Our class's data results showed that red light data showed the lowest gross rate. In Dark O ₂ consumption red and blue light both appear to commonly be negative numbers. White light seems to consistently produce positive numbers in each category. All of these results varied in comparison to other classes where all colors of Dark O ₂ consumption appeared to be negative, including white light. Our data shows a large range of numbers, meaning there was most likely human error which occurred in these experiments. Not all groups finished their experiments either, just leaving areas blank meaning there is not a complete and accurate average for all of these areas. The first number can be shown as being extremely high where the second is extremely low, with the third number missing it can be difficult to determine some common patterns. My specific group did not fully complete the full third set so we halted the process and calculated the predicted outcome, however, we cannot guarantee complete accuracy here. Other similar labs were found, however, their main focus tended to be on the amount of time that passed or the change, and results or the recorded temperatures and results. For example, an experiment was conducted with similar processes, but the goal was to calculate the light intensity in comparison to Co ₂ change. In this experiment the results showed that the carbon dioxide level within the respiration chamber decreased more rapidly with a high intensity of light. We were able to confirm that photosynthesis did take place in this experiment. This means the rate of photosynthesis will be increased with greater light intensity, but the cellular respiration will not be affected in this case (West Windsor-Plainsboro Regional School District n.d.) . When comparing these results to our experiment we can assume blue light will be considered to be more intense than other colors as it has the shortest wavelength. Upon further research I found

spinach leaves were an optimal choice for this experiment as they enhance the photosynthetic process. In this experiment we successfully created a photosynthetic reaction within the spinach, but alterations to evidence could occur for a variety of reasons. The top of the leaves must be facing the light to increase the rate of photosynthesis, if plants overheat they may wilt and stop functioning causing a decrease in number results, and a colder lab space could cause a decrease as cellular metabolism lowers. In the dark section, the CO2 rate value for leaves should be positive. This has biological implications because respiration produces CO2. As sugar is oxidized and broken down into CO2, water, and energy, this results in an increase in the concentration of CO2. On the other hand, the O2 value for leaves in the dark should be negative since O 2 is consumed during cellular respiration. Glucose is oxidized for energy while the amount of O 2 is decreased. We were able to see photosynthetic processes in light reactions and see the process of cellular respiration occur when O2 was limited while leaves were placed in the dark.

Citations A., N. (2019, April 13). Discovery of photosynthesis . Photosynthesis Education. https://photosynthesiseducation.com/discovery-of-photosynthesis/ Academy , K. (2015). Wavelengths of light and photosynthetic pigments (article) . Khan Academy. https://www.khanacademy.org/science/biology/photosynthesis-in-plants/the-light-dependent-reac tions-of-photosynthesis/a/light-and-photosynthetic-pigments Bassham, J., & Lambers, H. (1998, July 20). Photosynthesis . Encyclopædia Britannica. https://www.britannica.com/science/photosynthesis Gest, H. (2002). History of the word photosynthesis and evolution of its definition . Photosynthesis research. https://pubmed.ncbi.nlm.nih.gov/16245098/ Newton, J. (2019, November 22). What is the photosynthesis equation? Sciencing. https://sciencing.com/photosynthesis-equation-6962557.html Peterson, S., & Rapini, B. (2021, July 13). Photosynthesis (updated) . YouTube. https://youtu.be/CMiPYHNNg28 Renewable Energy Source (2022). Artificial photosynthesis . Artificial Photosynthesis - an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/engineering/artificial-photosynthesis Merriam-Webster. (n.d.). Photosynthesis. In Merriam-Webster.com dictionary . https://www.merriam-webster.com/dictionary/photosynthesis West Windsor-Plainsboro Regional School District. (n.d.). Using Vernier Co probe for obtaining photosynthesis /respiration rates . Using Vernier CO2 Probe for Obtaining Photosynthesis /Respiration Rates. https://www.ww-p.org/common/pages/DisplayFile.aspx?itemId=19335616

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Derak-Photosynthesis Lab Report Rough Draft

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