Photosynthetic Pigments: Background
PHOTOSYNTHETIC PIGMENTS LAB - PAPER CHROMATOGRAPHYPhotosynthetic Pigments: BackgroundThe photosynthetic pigments are responsible for absorbing and trapping light energy in theearly steps of photosynthesis. What benefits do the plants get by having several pigments?Also, what happens to leaves on deciduous trees in the Northern Hemisphere in autumn?The major pigments of photosynthesis are the chlorophylls. The two chlorophylls found ingreen plants are chlorophyll a (chl a) and chlorophyll b (chl b). Certain other chlorophylls(chlorophyll c and bacteriochlorophylls) are found in non-green algae, protistans, andphotosynthetic bacteria. Other pigments include carotenoids and phycobilins, sometimesreferred to as the accessory pigments. Carotenoids occur in all photosynthetic organisms, whilephycobilins occur in the red algae and cyanobacteria.In this experiment, the photosynthetic pigments from spinach leaves will be extracted andseparated using the technique of paper chromatography.ChlorophyllsChlorophylls are greenish pigments which contain a porphyrin ring. This is a stable ring-shapedmolecule around which electrons are free to migrate. Because the electrons move freely, thering has the potential to gain or lose electrons easily, and thus the potential to provideenergized electrons to other molecules. This is the fundamental process by which chlorophyllcaptures the energy of sunlight. As is the case for other compounds, the specific absorptionmaxima of any chlorophyll depends on the solvent in which it is dissolved.CarotenoidsThere are two classes of carotenoids, the carotenes and the carotenols. All carotenoids havelong isoprenoid chains, with alternating double and single bonds. Structurally, the carotenes arecomposed entirely of carbon and hydrogen, whereas the carotenols also contain oxygen in theform of hydroxyl or keto groups.TanninsTannins are a class of ergastic substances .i.e., non-protoplasm materials found in cells. In yoursample they may show up as a grey line. Tannins are distributed in species throughout the plantkingdom. Tannins are mainly physically located in the vauloles or surface wax of plants.The tannin compounds are widely distributed in many species of plants, where they play a rolein protection from predation, and perhaps also as pesticides, and in plant growth regulation.The astringency from the tannins is what causes the dry and puckery feeling in the mouthfollowing the consumption of unripened fruit or red wine. The destruction or modification oftannins with time plays an important role in the ripening of fruit and the ageing of wine.
PHOTOSYNTHETIC PIGMENTS LAB - PAPER CHROMATOGRAPHYPaper ChromatographyChromatography is a technique used to separate the components of a mixture. There arevarious types of chromatography (column, paper, thin-layer, gas), but in all cases the separationis achieved by distribution of components between a fixed or stationary phase and a moving ormobile phase. In paper chromatography, the components of a mixture are separable intodiscrete zones on a sheet of filter paper.For ascending paper chromatography, the appropriate solvent is added to the bottom of achromatography jar. The atmosphere in the jar should be saturated with solvent vapor prior toadding the paper. The paper is placed in the jar so that the streak is above the level of thesolvent. Then, the solvent moves up the paper by capillary action, past the sample, toward theend of the paper.During this process, termed development, the solutes separate and form a trail of discretebands on the chromatogram. Separation of the components is usually measured by the Rf(retardation value) value. The Rf value is given by the equation:Distance traveled by the soluteRf Distance traveled by the solvent from the originFor the numerator, the distance is measured from the origin either to the center or to theleading edge of each spot or band. The denominator is the distance from the origin to thesolvent front. The Rf values can be used to identify the various solutes when the experimentalconditions are very carefully controlled.Analysis of Spinach PigmentsThe photosynthetic pigments are extracted from spinach by grinding the leaves in acetone. Thepaper is then streaked with the spinach extract and suspended in a chromatography jarpreviously equilibrated with vapors of the solvent, a 9:1 mixture of petroleum ether andacetone.When separation is completed, identify the pigment bands by their colors and relative positionson the chromatogram. The major pigments appear in 5 bands: in order, from the origin to thesolvent front, they are chl b (olive-green), chl a (blue-green), violaxanthin (yellow), lutein(yellow), and b-carotene (yellow-orange). You may also see tanin (gray).
PHOTOSYNTHETIC PIGMENTS LAB - PAPER CHROMATOGRAPHYPhotosynthetic Pigments: ProceduresPreparationThe solvent mixture is extremely flammable; the chromatography should be carried out in afume hood. Before handling the paper, hands should be washed and thoroughly dried. Thepaper should be handled as little as possible and only on the edges.1. Obtain a piece of chromatography paper (about the length of the test tube). DO NOTtouch it with your fingers, only hold edges!2. Add the solvent mixture to the chromatography test tube. Add freshly prepared solvent(9 vols. petroleum ether *:1 vol. acetone, mixed well) to a height of approximately 2 cmand cap with a cork, set this aside while preparing the next steps. * CAUTION:Petroleum ether and acetone are extremely flammable and should be kept away fromheat, sparks, or an open flame.Preparation1. With a pencil and ruler, draw a light line across the width of the chromatography paper,about 3 cm from the bottom. This will insure that the extract, which will be streaked onthis line, is not immersed in the solvent. Make a light mark on each end of the line about1 cm from the edge of the paper.2. Using a capillary tube, make 10 streak applications of the pigment extract along the linebetween the two marks. Do not let the pigment touch the edge of the paper. Thecapillary tube is filled by immersing the tip in the extract. Hold the tube at a 45 o angleand draw it along the pencil line. Move your arm quickly so the pigment does not form alarge spot at the beginning of each streak.3. Streak each successive application in the direction opposite of the preceding one toinsure an even line at the end of the ten applications. Allow each application to air drybefore making the next. The final thickness of the streak should be no more than 6-7mm.4. Use paper clip and cork to place the streaked chromatography paper in the test tube.Allow the chromatogram to develop in the dark or in very dim light for 45-60 min. oruntil there is clean separation of the 5 bands. Stop the development before the solventfront reaches the end of the paper.5. Remove the chromatogram from the test tube and put a pencil mark at the leading edgeof the solvent front before it dries. Hang. Record the distance traveled by the solventfront and by the leading edge of each band. Also record the color of each band and whatpigment it contains.
PHOTOSYNTHETIC PIGMENTS LAB - PAPER CHROMATOGRAPHYMeasuring the Rf valueThe location of the solvent front in the example above is clear from the definition of the leadingedge of the wet area marked by the solvent (66mm) . The position of the solute is not sosimple, especially when there is "tailing" or a spread of the solute spot. The position of thesolute is taken to be where the "center or gravity" of the solute spot falls .The red dye movedfaster. The distance traveled is 57 mm. The "center of gravity" marks the average position ofthe solute molecules. Even for the same compound, some molecules move faster and someslower. The distance moved by the slow dye is 32 mm.The Rf value has a maximum value . The ratio of the distance travelled by the solute divided bythe distance travelled by the solvent can NEVER exceed a value of "1".The SOLUTE CAN NEVER LEAP AHEAD of the solvent.lab procedures modified cepts/labs/pigments/
PHOTOSYNTHETIC PIGMENTS LAB - PAPER CHROMATOGRAPHYPhotosynthetic Pigments: Questions (10 points total)NAME:DATE:1. Calculate the Rf value for each pigment.2. What do the Rf values indicate about the relative solubilities of the pigments in thesolvent?3. Why does a plant use several pigments instead of one or two? Why are plant leavesgreen?
The photosynthetic pigments are responsible for absorbing and trapping light energy in the early steps of photosynthesis. What benefits do the plants get by having several pigments? Also, what happens to leaves on deciduous trees in the Northern Hemisphere in autumn? The major pigments of photosynthesis are the chlorophylls.
Anoxygenic photosynthetic bacteria Some photosynthetic bacteria can use light energy to extract electrons from molecules other than water. These organisms are of ancient origin, presumed to have evolved before oxygenic photosynthetic organisms. Anoxygenic photosynthetic organisms occur in the domain Bacteria
The current systems of classification of algae are based on the following main criteria: o kinds of photosynthetic pigments, o type or chemical nature of photosynthetic energy storage products o photosynthetic membranes’ (thylakoids) organization and other features of the chloroplasts. o cell wall composition and structure. o the p
Plant pigments are colored molecules that absorb light at specific wavelengths. These molecules capture the energy of sunlight and use it to make their own food. For more information about the different types of plant pigments, provide this resource (or your own) for students to review: Photosynthetic Pigments Secondary Knowledge Provide .
Photosynthetic characteristics of cotton are enhanced by altering the timing of mulch film removal ZHANG Zhanqin1,2, ZHANG Li1,2, TIAN Haiyan1, NIU Yuan3 and YANG Xiangkun1,2* Abstract Background: The photosynthetic parameters of cotton plants may be modified by the timing of film removal during their growing period.
was to compare the photosynthetic characteristics and sto-matal traits of different photosynthetic organs in two wheat cultivars in response to water deficit during the grain-filling stage. We measured the distribution of stomata on the glume, lemma, and awn of the wheat spikes an
Food Chemistry Identification of natural pigments based on chemical behavior Background: Proper handling and preparation of fruits and vegetables includes preserving their natural, attractive colors. Red and orange pigments come from many sources, and while they
I. Chlorophyll and Chloroplasts 1. Light: wavelengths seen as visible spectrum colors . 2. Pigments: light-absorbing molecules in . photosynthetic organelle Thylakoids: saclike photosynthetic membranes a) . membranes Energy from Sunlight Chloroplast ATP O 2 NADPH NADP High Energy Sugars ADP P Includes
Alex Rider is not your average fourteen-year-old. Raised by his mysterious uncle, an uncle who dies in equally mysterious circumstances, Alex finds himself thrown into the murky world of espionage. Trained by MI6 and sent out into the field just weeks later, Alex [s first mission is to infiltrate the base of the reclusive billionaire suspected of killing his uncle. Filmic and fast-paced (the .
