photosynthesis lab write-up

Carbon Dioxide Concentration Dissolved in Solution Increases Ph otosynthesis with Light Energy Abstract: The object of this lab was to test how different environmental factors affect the rate of  photosynthesis in leaves. This was achieved by infusing equally-sized discs of spinach leaves with four solutions of varying carbon dioxide concentrations. The sodium bicarbonate solution was expected to have the fastest rate of photosynthesis, but this this did not prove to be true. true. The results for this solution were due to human error. error. It was concluded that the Coca Cola solution had the fastest rate of photosynthesis because the most leaf discs rose to the surface of that solution. Introduction: Photosynthesis, in the most general terms, converts carbon dioxide and water into oxygen and glucose with the use of sunlight energy. energy. Plants capture sunlight energy energy and carbon dioxide with chloroplasts. Within the chloroplasts, there are grana, or stacks of thylakoids. thylakoids. There are chlorophyll molecules on top of each thylakoid that capture light energy. energy. These energy-rich molecules move into the stroma where carbon is fixed into simple sugars. Carbon dioxide diffuses through through the cell membrane via passive transport. transport. As long as carbon dioxide is being consumed in photosynthesis, there will be a continuous gradient for  passive transport (Passive). The leaf anatomy consists of three layers: the palisade layer, layer, air space, and the spongy mesophyll. The spongy mesophyll is usually filled filled with carbon dioxide for photosynthesis and oxygen for cellular cellular respiration. The leaves became infused with  bicarbonate solution when the gases were extracted and replaced with the solution through the use of a vacuum. The materials of this lab are as follows: baking soda (sodium bicarbonate), liquid soap, 2  plastic syringes without the needle (10 mL or larger), larger), living leaves (spinach), hole punch, 4 clear  plastic cups, timer, timer, light source (light bulb/lamp), Coca Cola, Canada Dry Ginger Ale, distilled water, 1 pipette, plastic dish. One variable of this lab lab was the environment, specifically the the type and amount of carbon dioxide in the four different solutions. Another variable was the area from which each leaf disc came from; some were closer to the stem or veins, a nd some were closer to the leaf edge. A third third variable, which was quantitatively measured, was the amount of time it took the discs to rise to the surface of the solution. The constants include: light distance, time in solution, type of cup, origin of distilled d istilled water, water, bag/brand/age of spinach, size of leaf discs, and type of light. The hypothesis is if there is more carbon dioxide in the solution, more leaf discs will float to the surface because photosynthesis will occur faster and produce oxygen more quickly.

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Procedure: During the lab, be sure to handle light bulbs with care, as they could easily shatter. shatter. Keep all solutions away from the electrical cord of the lamp to prevent electrocution. Prepare 300 mL of a 0.2% bicarbonate solution and 300 mL of distilled water. water. Pour 3 cm of the bicarbonate solution into a clear plastic plastic cup, and 3 cm of distilled distilled water into another plastic plastic cup. Label the cups "with CO2" (sodium bicarbonate solution) and "without CO2" (distilled water) appropriately. appropriately. Add a drop of liquid soap into each plastic cup, while while avoiding suds. The soap will act as a surfactant that will draw the solution into the leaf by wetting the leaf's hydrophobic hydropho bic surface. Cut 10 leaf discs using a hole punch for each cup. Avoid punching discs on major leaf veins. To draw gases out of the spongy mesophyll of the leaves and an d replace the gases with solution, use the following steps; take the plungers out of the two syringes and place 10 leaf discs inside each syringe. Replace the plunger without without crushing the leaf discs. Put about 10 mL of solution into each syringe. Make sure all leaf discs discs are suspended and no air is is left in the syringe. Create a vacuum by holding a thumb over the the syringe opening while pulling back on the plunger. plunger. Hold the vacuum for for 10 seconds and then release the plunger. The discs should should sink in the solution because the solution should have infiltrated the spongy mesophyll of the discs. Repeat this process if the discs do not sink, but more than three attempts can damage the discs. Empty the syringes into the appropriate plastic cups. Place each plastic cup under the same light source. Start a timer, timer, and every minute, count how many discs have floated to the surface of the solution. Keep the timer running until all discs are floating. floating. Record observations.

Results and Data: Observations: With CO2 - 1:20 -- small ripples in solution (bubbles popping) - 7:10 -- disc lift - looked more murky than without CO2 - some sodium bicarbonate settled out of solution -- grains visible on bottom of cup ~ left out without stirring for approx. 30 minutes Without CO2 - no movement of discs - 4:08 -- a few bubbles

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Coca Cola - less bubbles than Ginger Ale - most discs rose half h alf way, fell slightly, slightly, moved laterally toward center, then rose completely - most discs bobbed before rising completely - 30:00 -- disc rise - 35:30 -- disc rise - 37:40 -- disc rise - 38:00 -- disc rise Ginger Ale - bubbles more rapid than Coca Cola - 36:00 -- disc rise

The table above shows the number of discs floating at 5 minute intervals in the sodium  bicarbonate solution and distilled water. water. Because of the lamp was far from the plastic cups on the first attempt, this portion of the lab lab was repeated twice. The sodium bicarbonate solution was left out and not stirred while the inquiry a nd re-do were set up, so some baking soda settled out of solution. Also, the amount of soap could have inhibited the solution from infiltrating the spongy mesophyll. We did not measure an exact amount of soap, so there could have been too much. Ultimately, Ultimately, none of the discs rose completely in either solution. However, one disc in in the sodium bicarbonate solution rose very slightly. slightly. The inquiry experiment was occurring at the same time as our re-do, and the two lamps were close together. together. The inquiry lamp was turned off after 8:42, and there was no disc movement after that point. The solutions were left under the lamps for less time than the inquiry solutions due to restricted time in class.

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The table above shows the number of discs floating at 5 minute intervals for the Coca Cola and Ginger Ale solutions. solutions. After 40 minutes, the Coca Cola solution had 6 floating discs and the Ginger Ale solution had 1 floating disc. disc. One uncertainty was the age of the the soda. If the soda was older, it would be more flat and there would be less CO2 than a newer soda. Additionally, Additionally, the soda was colder than the distilled water it was placed in, which could have slightly inhibited the rate of photosynthesis. Coca Cola and Ginger Ale contain different ingredients which could have favored, in Coca Cola, the rate of photosynthesis or restricted, in Ginger Ale, the rate of  photosynthesis. It is also unknown where on the leaf surface each leaf disc came from; some might have come from areas near the stem or veins and some might have come from the edge of the leaf. Also, some leaves could have been more wilted wilted than others, which would have negatively affected the rate of photosynthesis.

Based on the data and knowledge of what was supposed to occur in the experiment, the Coca Cola contained the most CO2 because the most discs rose; photosynthesis occurred the fastest, so oxygen bubbles were produced the fastest. However, no discs rose like they were supposed to in the sodium bicarbonate solution because most of the solute settled out of solution. The true relative amount of CO2 in the Coca Cola solution could not be determined because the results could not be accurately compared to the sodium bicarbonate solution. The lack of leaf movement in the distilled water was assumed prior to the test. The Ginger Ale solution solution fell somewhere in between in regards to to CO2 concentration, as 1 disc rose. rose. Based on the data obtained, the amount of CO2 in the solutions from least to greatest was distilled water, sodium  bicarbonate, Ginger Ale, Coca Cola.

Conclusion: The hypothesis was if there is more carbon dioxide in the solution, more leaf discs will float to the surface because photosynthesis will occur faster and produce oxygen more quickly. quickly. Based on the data, photosynthesis occurred faster in the sodium bicarbonate solution than the distilled water; there were more bubbles and one disc lifted in the sodium bicarbonate solution. Also based on the data, photosynthesis occurred faster in the Coca Cola solution than the Ginger Ale solution and the two other solutions; six discs rose in the Coca Cola solution, 1 disc rose in the Ginger Ale Ale solution, and no discs rose in the other two solutions. The hypothesis was supported because the Coca Cola solution had the most discs rise and the most bubbles, which

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respiration. Photosynthesis could have been occurring and producing oxygen, but the oxygen could have been metabolized at the same rate it was produced. This lab included a variety of limitations and human errors. errors. One human error was not measuring the amount of soap that was put into each solution. The amount of soap in each cup was not consistent. Too little soap would not allow enough solution infiltrate the leaf. Too much soap would allow too much soap and not enough solution to infiltrate the leaf. Time was limited limited  because of the classroom setting. Artificial light was used, which is not typically the light light energy  provided for plants to carry out photosynthesis. The method used to infiltrate the spongy mesophyll of the leaves does not occur in nature. Also, spinach leaves are not completely immersed in water in nature. The small size of the plastic cups only allowed for a very small amount of soda to be tested in the inquiry. inquiry. The results could have been more accurate if leaves that are typically immersed in water were used, like plants that normally grow under water. The results of this lab can be extended into lake pollution. Groundwater pollution from sewage hits the aquatic plants first. When the plants die, photosynthesis stops, and thus, oxygen  production stops. The other fish an animals living in the lake cannot live without that oxygen  production (Davis). Additionally, Additionally, eutrophication can occur when there are excessive nutrients in the lake. The excessive nutrients allow photosynthesis photosynthesis to occur too quickly and algae overgrows. overgrows. The algae takes over the lake, and no oxygen is left for the animals inhabiting the lake (Friedl). In future study, a variety of plants should be tested besides spinach, some that a re aquatic and some that are not. Natural sunlight instead of a light bulb would produce more accurate results. It would be easier to see results with more solution a nd more leaf discs.

Works Cited: Davis, Dave. "Water Quality - Lake Scientist." Lak e Scientist. Kent State University, University, n.d. Web. 08 Nov. 2015. Friedl, Sarah. "What Is Eutrophication? - Definitions, Causes, & Effects." Study.com. N.p., n.d. Web. 08 Nov. 2015. "Passive Transport Across Across Cell Membranes." ABPI. The Association of the British Pharmaceutical Industry, n.d. Web. Web. 8 Nov. 2015.

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