The suspects were tested individually at different wavelengths and intensities to find the optimal rate of photosynthesis by using a spectrophotometer, measuring the greatest change in absorbency. From this experiment, two data charts and four graphs were obtained. The hypothesis was set from graphs obtained in this lab, and the optimal reaction rate was found at a wavelength of 650 NM and an intensity of 50 Einstein/AMA/sec. Introduction Every species on earth needs some kind of energy sources in order to survive.
In animal cells, the mitochondria produce ATOP from cellular respiration. However, the plant cells have a different type of center that produces energy- chloroplasts. The main process of photosynthesis is the absorption of light by the pigments. The light energy absorbed is first transferred by exited electrons to reaction enters. Part of the light energy is stored in ATOP and NADIA through a series of electron carriers. ATOP and NADIA are the energy currency, which are further used for CO fixation and photoengraving. Plant Psychophysiology, 1996). The lab experiment deals with wavelength and intensity, which are the two most important variables in the photosynthesis process. Being easily found in the leaves, chloroplasts are located in plant cells. The photosynthesis process takes place inside the chloroplasts, which are stacked in ayatollahs called grain. The area between the ayatollahs and the inner membrane is called the tromp (Campbell, 2002). The light reactions of photosynthesis take place in the ethylated while the Calvin cycle occurs in the stoma.
The chemical equation for photosynthesis is shown below. CHIC + OOH( light energy ( C6H1206 + 602 + AH During the day, plant-cells consume carbon dioxide, water, and light energy to form carbohydrates, oxygen, and water. At night, photosynthesis stops and plant-cells consume oxygen as animal cells (The Life of Plants, 2002). Through reducing NADIA+ into NADIA and producing ATOP by the addition of a phosphate group to ADAPT, the light reactions alter light energy to chemical energy.
The Calvin Cycle then yields light reactions- NADIA and ATOP along with CO to produce carbohydrates (Campbell, 2002). Due to its dependence on the products of light reactions, the Calvin Cycle, which indirectly accepts light energy, only occurs in the day light. Chlorophyll is the photosynthetic pigments on the ayatollahs. In this lab, we measured the amount of light absorbed from each experimental cavetti with a spectrophotometer, which varies over time due to the relations with DICED- the artificial electron acceptor.
As DICED is reduced, the amount of absorption will decrease and the sample will become colorless. This was the demonstration made by Robert Hill in 1938, known as “The Hill Reaction” (Advanced Biology, 2000). The study of Emerson and his associates at the University of Illinois in the asses found that the most effective light for photosynthesis in chloral were red from 650 NM to 680 NM and blue from 400 NM to 460 NM, which were the strongest absorbed colors by chlorophyll (Light-Harvesting Antennas in Photosynthesis, 2003).
The reaction rate of photosynthesis varies with light intensity, and as the light intensity increases the reaction rate also increases only up to a certain point (Advanced Biology for You, 001 From the given information, the hypothesis was that the optimal reaction rate was expected to be at the wavelength near 450 NM and 650 NM. Also, for the optimal reaction rate for different intensities should be at 50 Einstein/AMA/sec. Materials and Methods This lab consisted oft main experiments, one with the intensity of light and the other with wavelengths of photosynthesis.
The spectrophotometer was turned on 15 min prior to the experiment. For each different intensity levels, 2 suspects were prepared (one for the experimental variable and one for the control variable). Also, 2 suspects were prepared for each different wavelength. Two blanks were prepared for the entire experiment (one for intensity, one for wavelength). The experimental cavetti for intensity consisted of 2. 5 ml of 2. 5 ml DICED, 2. 0 ml water, 2. 0 ml PEP buffer, and 0. 2 ml chloroplasts, a total of 6. 7 ml. The control cavetti for intensity was the same as the experimental cavetti for intensity.
The experimental cavetti for wavelength consisted of 2. 5 ml DICED, 1. 7 ml water, 2. 0 ml PEP buffer, and 0. 5 ml chloroplasts a total of 6. 7 ml. The blank cavetti intensity contained 4. 5 ml of water, 2. 0 ml of PEP buffer, and 0. 2 ml chloroplasts for a 6. 7 ml. The wavelength blank was composed of 4. 2 ml water, 2. 0 ml PEP buffer, and 0. 5 ml chloroplasts for a 6. 7 ml. Before starting the experiment, we set the wavelength at 600 NM, placed the blank cavetti into the spectrophotometer, and set the absorbency at zero. The laboratory was kept dark during the experiment to prevent light pollution.
To check the absorbency at different wavelengths, we first placed the blank cavetti into the spectrophotometer and set the absorbency to zero. Control suspects had to be covered by aluminum to prevent them from light exposure. We then placed all the suspects into the ice bath to cool them down. Each ice bath was then exposed to lights at different wavelengths (blue 450 NM, green 545 NM, red 650 NM and far red 750 NM) for intervals of 2 minutes up to 16 minutes. After exposing the light for two minutes, the experimental and control suspects were placed into the spectrophotometer and the absorbency were obtained.
For the absorbency readings at different intensities of light, most of the process was the same, except for the suspects that were exposed to light at different intensities (distance). Each experimental cavetti was placed into the ice bath along with aluminum foil, which covered the control cavetti. The ice baths were placed at four different intensities. The intensities were at 5 Einstein/AMA/ sec, 175 Einstein/AMA/sec, 50 Einstein/AMA/sec, and 3 Einstein/mm/sec. Eke the wavelength experiment, the ice bath was exposed to the light for 2 to 16 minute intervals while each interval absorbency was recorded.
After obtaining all the absorbency, the records were gathered into one data chart. Results From the raw data chart, four different graphs were acquired. Figure 1 shows absorbency readings at different wavelengths over a time period. The graph shows that the wavelength of 650 NM has the steepest slope out of all the efferent wavelengths. As time passes, absorbency went down from 1. 30 to 0. 62. Also, the change of the slope at wavelength of 450 NM is evident. A little bit of the slope change is shown at the wavelength of 750 NM; however, during the experiment, the wavelength at 545 NM showed no change.
Figure 3 in relation to Figure 1, shows the reaction rate for each wavelength. The optimal reaction rate was found at 650 NM, and no reaction was found at 545 NM. Figure 2 represents the absorbency readings over the reaction time at different intensities of light. The intensity level at 5 and 50 ? Einstein/AMA/sec almost reached 0 as the time passed. Not much change was shown at intensity levels of 175 and 3 ? Einstein/AMA/sec. Figure 4 supports Figure 2, which shows the reaction rate of photosynthesis when put under different intensities of light. The optimal reaction rate was found at 50 ?
Einstein/AMA/sec followed by 5 ? Einstein/AMA/sec. Discussion Despite some unexpected results, the overall result of the experiment proves the hypothesis made. The hypothesis was that optimal reaction rate was expected to be at the wavelength of 450 NM and 650 NM. For instance, in Figure 1 and Figure 3, it shows that the maximum reaction rates are at 650 NM and 450 NM. The optimal photosynthesis reaction rate was at 650 NM because the shorter wavelength acquires excessive energy, while the longer wavelength did not take enough energy. Also, chlorophyll includes pigments that absorb more at particular wavelengths.
The experiment showed poor absorption made by pigments at wavelengths of 545 NM and 750 NM. There were a couple unexpected results that were found in these two graphs. One was the wavelength of 545 NM; no changes were made throughout the entire lab experiment. Some mistakes were made by students, since the entire samples were supposed to be exposed to light, photosynthesis should have occurred. Also, the study shows that a small reaction peak was found at 545 NM (Photosynthesis Research Protocols, 2004). Another unexpected result was the absorbency change in the control suspects.
Because the control suspects weren’t exposed to lights, there should not have been any absorbency change. While measuring the absorbency of the control, it was exposed to light. Figure 2 shows that at the intensity of 50 ? Einstein/AMA/sec photosynthesis was most effective, followed by 5 ? Einstein/AMA/sec and 3 ? Einstein/AMA/sec. The reaction rate at the intensity of 1 75 ? Einstein/AMA/sec had the lowest reaction ate, which was quite unexpected from the hypothesis. Because the study shows that the reaction rate increases up to a certain point, it did not state that it would decrease.
A possible reason for error is due to the light pollution during the lab. The contamination of the control suspects, while the aluminum was removed for measuring absorbency by spectrophotometer would cause inconsistent data. Another reason for error could be caused by the temperature of the suspects. As the ice in the bath melts the chlorophyll, enzyme might not have performed effectively. To prevent and improve this experiment, students should be careful tit light contamination and the temperatures of the suspects. The student should also work on the experiments more precisely; for example, reading and measuring skills.