This captured energy is used to convert carbon dioxide into complex energy-rich molecules that can be used by themselves or other organisms. “Photosynthesis is the conversion of light energy to chemical energy in the form of sugar and other organic molecules. ” (Russell, Wolfe, Hertz, & Starr, 2010). Photosynthesis can be categorized into two main processes: light-dependent reactions and light-independent reactions. For the purpose of this lab, light- dependent reactions will be investigated.
The reactants involved in photosynthesis include carbon dioxide, water and sunlight to produce glucose, oxygen, and water.
The light reactions involve the capture and use of light energy by pigment molecules to synthesize NADIA and AT P. Plants use this light energy to produce glucose from carbon dioxide. The glucose is stored mainly in the form of starch granules, in the chloroplasts of cells. Glucose in the form of starch is non-polar and is not soluble in water, allowing it to be stored much more compactly.
The chloroplast is formed from an outer membrane, an inner membrane, and an intermediate compartment.
The aqueous environment within the inner membrane is called the stoma. Within the stoma is the ayatollahs, which are flattened, closed sacs. It is in these sacs that the specific molecules required to carry out the light reactions of photosynthesis are contained, including the pigments, electron transfer carriers, and the TAP syntheses enzymes for TAP production. A pigment is able to absorb photons of light and differ by the wavelengths of light they can absorb.
The amount of energy in a photon is inversely related to its wavelength.
Blue light has a shorter wavelength and consists of photons that have higher energy than the longer wavelength red light. When photons of light hit an object, they can be reflected off the object, transmitted through the object or absorbed by the object. The absorption of light by a pigment results in electrons becoming excited and moving to a higher energy state. Color is determined by the wavelengths that it cannot absorb, therefore chlorophyll is green since it does not absorb green light.
If a pigment absorbs all wavelengths of visible light, the object appears black. A large variety of pigments can be found in plants. The most common are chlorophyll a and b and carotids, located in he chloroplasts of cells, and anticyclones, located in the cell vacuoles and do not contribute to photosynthesis. Each of these pigments has different properties and performs different functions for the plant, including absorbing light in different parts of the spectrum. The more light absorbed equals the more energy available for a plant.
The pigment molecules that can be found in plants are specifically arranged in and around photometers that are embedded in the ethylated membranes of chloroplasts. Each contains a reaction centre surrounded by an antenna complex. Light from the sun travels into the holocaust and goes through the antenna pigment. The energy trapped by the antenna complex is funneled to the reaction centre, called IPPP, where it is used to oxidize a chlorophyll molecule and donate an electron to a primary acceptor molecule to continue into carbon fixation to ultimately release glucose sugar (Oracle Thinkers, 2010).
The reaction centers are named after the wavelength (in manometers) of their red-peak absorption maximum. Most plant parts, especially leaves, contain some combination of the three main pigments, even if only one is especially obvious. It is possible to separate these segments from each other using a technique called paper chromatography. In this process, plant tissue extract is applied to a piece of chromatography paper. “A solvent is allowed to travel up the paper, and if the pigment is soluble in the solvent, it will be carried along with it. (Benny, 2009) Different pigments have different affinities for the solvents or polarity and will travel at different rates. Chlorophyll, anticyclones, and carotids are typically non-polar. For lab 12, it is hypothesized that chlorophyll a and b are present in a plant leaf and contribute to the starch production in photosynthesis. Also, products of photosynthesis will be present in leaf tissue exposed to red and blue light wavelengths for several days, but a decreased presence in leaf tissue exposed to green and black light wavelengths.
In lab 13, it is expected that since chlorophyll a and b are more polar and smaller molecules than the anticyclones and carotids, they will travel higher up the chromatography paper than the other pigments. Materials and Methods Lab 12 In the first part of this laboratory experiment, a multi-colored leaf was removed from a Coleus plant that was in direct sunlight for several hours. The hypothesized results for which pigments were present and the results of an kill starch test were then recorded.
A boiling alcohol bath was set up, which consisted of a IL beaker containing mall of water on a hot plate, and a mall beaker containing mall of 80% ethyl alcohol inserted into the larger water beaker. The water was brought to a slow boil and the leaf was placed into the boiling alcohol solution in order to extract the pigments. When the leaf became almost white, the leaf was removed, placed into a Petri dish, and covered with distilled water. KAKI solution was added to the distilled water until a pale amber lour was obtained.
The leaf produced a purple-black color in some areas which show a positive test for starch. In the second part of the lab, part of a leaf was taken from a germanium plant that had been covered for several days with different color filters: blue, green, red, and black. In order to differentiate between the leaves taken from different filters, the black filter leaf had one notch taken from leaf, the green had 2 notches, the red had 3 notches, and the blue had 4 notches. The leaves were then place into the alcohol bath that was used in the first experiment.
When the leaves became mostly white, they were removed using forceps, placed into a Petri dish, and rinsed and covered with distilled water. Kill was added to the distilled water until an amber color was achieved. The observation of the reaction of the leaves with the kill after 5 minutes was then recorded. See appendix for original lab report. Lab 13 In this laboratory experiment, pieces of spinach leaves were mashed in a mortar and pestle in order to extract the plant’s pigments. These pigments were transferred to a piece of chromatography paper with a marked pencil line CM room the bottom by means of a capillary tube.
The chlorophyll pigment was allowed to dry and was re-applied 5 times, drying between each application. The chromatography paper rolled and stapled and was placed into a jar containing a petroleum ether and acetone solvent. The chromatography was allowed to proceed until the solvent reached about CM from the top. The paper was removed and examined for separations of pigments. See appendix for original lab report. The control for the overall experiment was the original leaf taken from the Coleus plant in lab 12, both before and after the 121<1 solution was added.
The leaf before the kill is used as a reference to the ones that were left under filters because it contained different color and it was grown under normal light. After the KAKI solution was added, the results from the original leaf were compared to the filtered leaves. If the color of the filter light had an effect on the photosynthesis taking place there, a comparison to the colored leafs colored spots could confirm this. The negative control was the black filter leaf because no light would be filtered through, showing a large decrease in photosynthesis.
A intro that should have been added to lab 12 part A is a fully green leaf should have been used first, and then a colored one, in order to see the positive starch pigment change. A control that should have been added to lab 12 part B is a leaf should have been taken from the plant that did not have a filter covering it. Results and Observations Colors and Pigments Present in a Coleus Leaf Color Pigmentation’s present (predicted) + or Geographically a and b ++ Purple Anticipations – Pink Anticipations – White No pigments present – Green/Purple Chlorophyll a and b ++ Starch present (actual) + or
Coleus leaf before kill outcries leaf after kill test Geranium Leaves Filter Color Before KAKI test After kill test Black Green Red Blue Chromatography Paper The table of the coleus leafs pigments shows the pigments contained within certain colored areas of the leaf that were predicted before the 121<1 test. Beside is the actual pigments contained in the leaf after the 12Kl test was performed. Chlorophylls a and b were predicted and found positive for starch in the green coloured areas of the plant leaf, as well as in the purple/green area.
Anticyclones were predicted and found negative for starch presence n the purple and pink colored sections of the leaf. White parts contained no pigments. The colored filter plant leaves showed different results with the kill test. The blue and red filter leaves showed purple and purple/black change, a positive for starch increase, the green filter plant had a slight decrease in starch present, and the black filter did not let any light through, showing a large decrease in starch production.
The chromatography paper shows the separated bands of pigments that were isolated from the spinach leaves. The higher a band is, the more polar the pigment. Carotene pigment is yellow and that is the highest band that we see. Discussion In the first part of lab 12, the predicted and actual results for which pigments were present in a Coleus leaf and the results of the ASK’ starch test were tested and proved. Chlorophyll a and b were discovered to be positive for starch in the green colored areas of the plant leaf, indicating that a green color in plants produce these pigments.
It also proves that the green parts in plants perform the most photosynthesis to produce starch. Anticyclones were found to be negative for starch production in the purple and pink colored sections f the leaf, supporting the prediction that anticyclones do not play any part in photosynthesis. The white parts of the Coleus leaf contained no starch and therefore no pigments, due to the fact that white absorbs all spectrums of light and photosynthesis needs this light to produce the starch.
Even though the tip of the Coleus leaf contained a purple color, there was also green present too, on the underside of the leaf, and the colors combined to create a green/purple. This tip gave a positive reaction to the kill test, indicating that even though there was purple pigments, chlorophyll a and b were present to produce starch. In part B of lab 12, the effects of different wavelengths on plant starch production was examined. The results show that with the blue and red filter leaves the kill test had a positive purple and purple/black change, indicating the presence of starch, perhaps even an increase.
Since chlorophyll a and b absorb light best in the blue and red spectrums and there was only red or blue filtered light reaching the plant, there should have been an increase in starch production. As said before, the more light that is absorbed by the plant, the more energy that is available for a plant. With the green filter plant leaf, the results show that there was little to no starch production. This is to be expected. If the light reaching the plant is all green, the chloroplasts will not absorb the light. They absorb all other colors except green, which they reflect.
If there is no light except green reaching the plant, there is no photosynthesis taking place, and therefore no starch production. Even the areas on the leaf that were slightly more yellow did not react to the kill solution, though this could be due to the cells dying. The black filtered leaf ended up having a small reaction with the kill solution where turned dark gold. This would indicate that there is starch being produced from photosynthesis. This was an unexpected result. The black filter leaf ended up having more of a positive reaction in the kill than the green filter leaf.
This would mean that the leaf was somehow able to use light to produce starch in certain areas and not able to produce it in others. Theoretically, black is not a color that is successful at aiding photosynthesis due to the fact that black absorbs all light. The black filter should have absorbed all light spectrums reaching the leaf. (Fuhrman & Fuhrman, 2004). With all of the wavelengths being absorbed, there are none left to be transmitted into the leaf for photosynthesis. Without this light energy, starch is not being produced in the chloroplasts at all.
When the results of the black filtered leaf were compared to another group’s experiment, it was found that their leaf had the desired effect from the kill solution, showing no signs of starch. Therefore, as an experimental error, the leaf that we had taken might have been exposed to more light than the leaf the other group had taken, or the leaves were not fully covered by the black filter. Also, the 4 days that the plant was covered with the filters may not have been sufficient to gain the desired results from all the leaves.
In lab 13, the chromatography paper containing the isolated spinach pigments was analyzed. As seen in the results, there are 4 distinct colors on the paper. Starting at the top to bottom, the bands of colors are yellow/orange to indicate carotenes, blue/green to indicate chlorophyll a, yellow/green to indicate chlorophyll b, and olive green to indicate epiphytic. Different plant pigments have different structural groups. If the cement contains a high amount of hydrocarbons, it will end up having a non- polar polarity. If there are oxygen groups attached to the hydrocarbons, the pigment becomes more polar.
Since the experiment employs a highly non-polar solvent (petroleum ether and acetone), the pigments that are most polar will have the largest running distance on the chromatography paper. That is why we see such distinctive pigment separation. The pigments are separated based on the polarity of the hydrocarbon chain. Conclusion Of the two labs performed the hypotheses where correct in some ways and for some were incorrect. For lab 12, it was hypothesized that chlorophyll a and b were present in a plant leaf and would contribute to the starch production in photosynthesis.
Also, products of photosynthesis will be present in leaf tissue exposed to red and blue light wavelengths for several days, but a decreased presence in leaf tissue exposed to green and black light wavelengths. It was found that the red filter showed more starch content overall followed by blue, black, and green paper. The fact that green light would show less starch than black was not considered. In lab 13, it was expected that since chlorophyll a and are more polar and smaller molecules than the anticyclones and carotids, they will travel higher up the chromatography paper than the other pigments.