Bio 1120 7 lab report - photosynthesis PDF

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Koli 1 Khushi Koli Bio 1120 Photosynthesis

Introduction Photosynthesis is the mechanism by which plants use light to convert water and carbon dioxide to produce food, allow growth and release oxygen into the atmosphere. Life requires photosynthesis. Without it, there would be no potential for life. In some way, all living things use photosynthesis. Autotrophs, including plants and algae, can use light for later use to store and extract energy. Green algae (phylum chlorophyta) are land plants ' closest living relatives. These range from single to multi-celled organisms, and share with the land plants some cellular and physiological characteristics. This experiment was introduced as such so that it could be investigated that the white light with different distances and the wavelengths of other visible lights that we used like, red, green and blue affected the rate of photosynthesis created by observing the pH change. The more CO2 in an aqueous solution, the more acidic it becomes the solution. The experiment's algal beads will be surrounded by a solution of CO2 markers. Because CO2 is used for photosynthetic reactions, this means that the solution undergoes a color change. The solution is yellow-orange when there is relatively more CO2. The colour tends to purple when CO2 is used. A spectrophotometer set at 550 nm can be used to measure the color intensity. The more violet the solution at this wavelength, the higher the absorbance reading. Respiration will produce CO2, while it will be taken up by photosynthesis. Therefore, if the respiration rate is higher than the photosynthesis rate, the concentration of CO2 will rise and

Koli 2 the pH will decrease. In comparison, if the rate of photosynthesis is higher than the rate of respiration, the concentration of CO2 will decrease and the pH will increase.

Methods In this experiment, an alternate protocol was used which was given to us by the TA. We didn’t use the experiment given in the Lab manual. Instead of elodea leaves, the photosynthesis rate was observed using algal beads. There were 7 cuvetted prepared before lab. All cuvettes contained algal beads and 1.5ml of CO2 indicator solution. Each group was handed one cuvette and one light condition to work under. There were 7 different light conditions with different wavelengths and distances; Dark, red light 20cm , green light 20 cm, blue light 20cm , 20cm, 30cm, 40cm from the white light source. Our group had the green light. We recorded an time and absorbance for the cuvette and placed it in its correct incubation position, making sure all the beads were in a single layer. Then, we recorded the ph change and absorbance for every five minutes, for 45 minutes.

Results TABLE 7-1: pH and A550 Readings for Algal Bead Photosynthesis and Cellular Respiration Laboratory

Koli 3 Time (min)

Dark pH, A550

Red pH, A550

0

7.7, 0.81 8.2, 0.669

7.7, 0.44 8.3, 1.16 0 8.5, 1.49 0 8.7, 1.30 1 8.8, 1.49 4 8.9, 1.63 8 9.1, 2.52 7 9.1, 2.24 1 9.1, 2.41 2 9.1, 2.34 8

5

10

7.9, 0.912

15

7.7, 0.602

20

7.9, 0.710

25

7.9, 0.462

30

7.9, 0.044

35

7.7, 0.448

40

7.9, 1.14

45

7.7, 1.629

Gree n pH, A550 7.5, 0.6 8.1, 0.75 6 8.2, 1.93 2 8.3, 0.95 1 8.4, 0.97 6 8.4, 1.41 0 8.3, 1.56 8.3, 0.88 7 8.5, 1.94 4 8.5, 0.92

Blue pH, A550 7.7, 0,53 8.1, 1.58 4 8.3, 1.46 0 8.6, 1.66 8 8.7, 1.47 5 8.9, 1.81 2 8.9, 1.74 9 9.0, 1.80 1 9.0, 2.58 8 9.1, 2.45 4

White, 15 pH, A550 7.5, 0.82 8.5, 0.67

White, 20; pH, A550 7.7, 0.39 8.1, 1.13

White, 30 pH, A550

8.9, 1.150

8.7, 1.38

8.7, 1.921

8.9, 2.061

8.9, 2.10

8.7, 2.349

8.9, 1.377

9.1, 2.30

8.7, 2.385

8.9, 2.105

9.1, 2.30

8.9, 2.363

8.9, 2.010

9.1, 2.08

8.9, 2.382

8.9, 1.70

9.1, 1.85

8.9, 2.561

8.9, 2.135

9.1, 2.04

8.9, 2.103

8.9, 1.763

9.1, 2.311

8.9, 2,542

7.5, 1.0 7.7, 1.387

Koli 4

Conclusion The rate of photosynthesis is fastest when exposed to blue and red light, but not green. Because most of the green light is not absorbed and reflected back, giving the plants a green color. White light with the distance of 20 cm is the optimal intensity, as the rate is faster than the white light with the distance of 15cm and 30cm; white light with the distance of 20cm has the highest rate of photosynthesis comparing the other two white lights, hence, higher ph. The dark cuvette has the highest rate of CO2 production, hence, lower pH because in dark Co2 produced by cellular respiration and there is not much photosynthesis due to lack of light in order for the CO2 to get converted to glucose and decreasing the CO2 level.

Koli 5 Most difference regarding the results are due to the experimental error or environmental conditions. Errors could’ve also been cause due to the fluctuating results of the spectrometer. Also, there can be an error in the results if the beads weren’t flattened on the surface. The CO2 indicator will turn more alkaline under lights as the algal beads photosynthesize faster than they respire, resulting in have less CO2 left and hence, higher pH. Cellular respiration decreases the observed rate of photosynthesis by producing CO2, making the obsevered rate of photosynthesis lower. The dark cuvette is placed under light with a foil wrapped around it because different conditions can affect the rate of photosynthesis, like, the heat of the lamp, etc. but when we wrap it in foil, the conditions are constant. CO2 was the most alkaline under red light, blue light and white light with the distance of 20 cm. That is because the wavelength of these colours are high and are absorbed. Hence, more CO2 is produced but also getting occupied with the cellular respiration, that’s why less CO2 left, higher the pH. The white light distance of 20cm is the optimal distance for photosynthesis. Some plants contain accessory pigment than chlorophyll because accessory pigments gives them access to greater wavelength than chlorophyll cant get.

Koli 6 Works Cited Krane, D. (2018-2019). Bio 1120: A Laboratory Perspective. Cincinnati, OH: Van-Griner http://www.sjsu.edu/biology/assessment/introductory-core-redesign/Photosynthesis%20Lab.pdf...