photosynthesis pigments Pigments: Pigments are "molecules that absorb specific wavelengths (energies) of light and reflect all others." Pigments are colored: the color we see is the net effect of all the light reflecting back at us. Now, what do I mean by absorb? Electrons in molecules can exist at specific energy levels. Normally they exist at the lowest possible energy level they can. However, if enough energy comes along to boost them into the next level, they can "absorb" that energy and occupy that higher level. This is what pigments do. The light they absorb contains' just the right amount' of energy necessary to push them into the next level. Any light that does not have enough or has too much energy can not be absorbed and is reflected. The electron in the higher energy level, however, does not 'want' to stay there(i.e. it is unstable). It 'wants' to return to its normal lower energy level. In order to do this it must get rid or release the energy that has put it into the higher energy state to begin with. This can happen several different ways: 1) The extra energy can be converted into molecular motion and lost as heat.

2) Some of the extra energy can be lost as heat energy, while the rest is lost as light. This re-emission of light energy is called florescence. 3)The energy, but not the e- itself, can be passed onto another molecule. This is called resonance. 4)The energy and the e- can be transferred to another molecule. Plant pigments usually utilize the last two of these reactions to convert the sun's energy into their own. When chlorophyll is isolated from the enzymes it is associated with, the second scenario can be seen to happen. What should be the ideal pigment for chloroplasts? A collection of pigments that would absorb all light and thus appear Black seems a logical choice... but in fact we know this is not true.. plants except for some of the red algae appear green or brown, not black. Why? a number of possible explanation occur... IF plants had pigments that absorbed UV and x-rays this would mean that so much energy could be absorbed in light areas that electrons could be knocked off their orbitals and the molecule destroyed..

IF plants absorbed IR and radio waves, there would not be enough energy for electron transfer, just enough to warm up the molecule Pigments that absorb in the visible region gain just enough energy to boost an electron to the next level... However even in this region, not all visible wavelengths are abosrbed..there is some speculation that in the early competitive wars between photosynthetic bacteria [ and we mean early 3 BYA] , plants specialized so that some would absorb in the red, others green or blue. The survivors in the long run are the one with pigments that absorbed in the red/blue reflecting green.... at least on land. What are these Pigment involved in Photosythesis?: Chlorophyll a: This is the most abundant pigment in plants. Chlorophyll a absorbs light with wavelengths of 430nm(blue) and 662nm(red). It reflects green light strongly so it appears green to us. It contains a hydrophobic (fat soluble) phytol chain that allow it to be embedded in a lipid membrane. The rest of the structure called a tetrapyrrolic ring rests outside of the membrane . It is this part of the pigment that absorbs the energy from light.

The metal at the center of the structure, Mg, can have variable oxidation states . This means that it can accept and donate e- readily depending of the situation. Its flexible, which is very important to the function of the molecule. Chlorophyll b: This molecule has a structure similar to that of chlorophyll a. It absorbs light of 453nm and 642 nm maximally. It is not as abundant as chlorophyll a, and probably evolved later. It helps increase the range of light a plant can use for energy. Carotenoids: This is a class of accessory pigments that occur in all photosynthetic organisms. They are completely hydrophobic (fat soluble) and exist in lipid membranes. Carotenoids absorb light maximally between 460 nm and 550 nm and appear red, orange, or yellow to us. The most important function of carotenoids seems to be protecting the plant from free radicals formed from ultra violet or other radiation. Free radicals are dangerous because they contain an extra odd e- they don't really want to have. This means that they are constantly trying to get rid of this extra electron. They do this by attacking whatever bonds they can.

In animal systems it is speculated that: Vitamin E + radical oxidized ---> radical + Vitamin E oxidized Vitamin E oxidized + carotenoids ----> Vit E + carotenoids oxidized Carotenoids oxidized + Vit C ---> carotenoids + Vit C oxidized In animals, the Vit C can be flushed out of the system since it is soluble in water which none of the other molecules are. Whether this same series of transfers occurs in plants is unknown. In humans, taking Vit E or betacarotenes in themselves is not protection against oxidants unless there is a supply of Vit C to flush it out.. Smokes who maintain low levels of C are not helped with increases of the other 2. In plants, as the vacuole is a generally safe aqueous repository, the oxidized C may end up here, whereas carotenoids could not .... Xanthophylls are a fourth common class of pigments. They are essentially oxidized Carotenoids and contain oxygen. They are usually red and yellow and do not absorb energy as well as cartenoids. They are also fat soluble. Anthocyanins are a fifth class of pigments.

These pigments contain Cu and are stored in the vacuole of a plant because they unlike the other fat soluble pigments are water soluble. Note the structure of the phycocyanins we in the red algae and BG's. How does it differ substantially from the above pigments? Chlorophyll | Causes of Color A page from the "Causes of Color" exhibit... What is the role of chlorophyll? Chlorophyll is responsible for the lush green hues of many plants. Why do some plants appear green? Green plants are green because they contain a pigment called chlorophyll. Chlorophyll absorbs certain wavelengths of light within the visible light spectrum. As shown in detail in the absorption spectra, chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum. Green light is not absorbed but reflected, making the plant appear green. Chlorophyll is found in the chloroplasts of plants. There are various types of chlorophyll structures, but plants contain chlorophyll a and b. These two types of chlorophyll differ only slightly, in the composition of a single side chain.

Absorption spectra showing how the different side chains in chlorophyll a and chlorophyll b result in slightly different absorptions of visible light. Light with a wavelength of 460 nm is not significantly absorbed by chlorophyll a, but will instead be captured by chlorophyll b, which absorbs strongly at that wavelength. The two kinds of chlorophyll in plants complement each other in absorbing sunlight. Plants are able to satisfy their energy requirements by absorbing light from the blue and red parts of the spectrum. However, there is still a large spectral region between 500 and 600 nm where chlorophyll absorbs very little light, and plants appear green because this light is reflected. What is chlorophyll? Chlorophyll is a compound that is known as a chelate. A chelate consists of a central metal ion bonded to a large organic molecule, composed of carbon, hydrogen, and other elements such as oxygen and nitrogen. Chlorophyll has magnesium as its central metal ion, and the large organic molecule to which it bonds is known as a porphyrin. The porphyrin contains four nitrogen atoms bonded to the magnesium ion in a square planar arrangement.

Chlorophyll occurs in a variety of forms. The structure of chlorophyll a. Chlorophyll does not contain chlorine as the name might suggest; the chloro- portion stems from the Greek chloros, which means yellowish green. The element chlorine derives its name from the same source, being a yellowish-green gas. How do birds and animals see plants? Vegetation will not appear to animals as it does to us. Although our color perception is the most advanced amongst mammals, humans have less effective color vision than many birds, reptiles, insects and even fish. Humans are trichromats, sensitive to three fundamental wavelengths of visible light. Our brains interpret color depending on the ratio of red, green and blue light. Some insects are able to see ultraviolet light. Birds are tetrachromatic, able to distinguish four basic wavelengths of light, sometimes ranging into ultraviolet wavelengths, giving them a far more sensitive color perception. It is hard for us to imagine how the world appears to birds, but they will certainly be able to distinguish more hues of green than we do, and so are far more able to distinguish between types of plants.

We can speculate that this is of great benefit when choosing where to feed, take shelter and rear young. Aquatic creatures, from fish to the hyperspectral mantis shrimp (which distinguishes up to twelve distinct wavelengths of light) are uniquely tuned to the colors of their environment. The pages on animals include more information on the variety of color vision in the animal kingdom. The vivid colors of fall leaves emerge as yellow and red pigments, usually masked by chlorophyll, are revealed by its absence. Chlorophyll decomposes in bright sunlight, and plants constantly synthesize chlorophyll to replenish it. In the fall, as part of their preparation for winter, deciduous plants stop producing chlorophyll. Our eyes are tuned to distinguish the changing colors of the plants, which provide us with information such as when fruits are ripe and when the seasons are starting to change. Apart from coloring, has chlorophyll any other role? The green color of chlorophyll is secondary to its importance in nature as one of the most fundamentally useful chelates. It channels the energy of sunlight into chemical energy, converting it through the process of photosynthesis. In photosynthesis, chlorophyll absorbs energy to transform carbon dioxide and water into carbohydrates and oxygen.

This is the process that converts solar energy to a form that can be utilized by plants, and by the animals that eat them, to form the foundation of the food chain. Chlorophyll is a molecule that traps light - and is called a photoreceptor. Photosynthesis Photosynthesis is the reaction that takes place between carbon dioxide and water, catalysed by sunlight, to produce glucose and a waste product, oxygen. The chemical equation is as follows: Glucose can be used immediately to provide energy for metabolism or growth, or stored for use later by being converted to a starch polymer. The by-product oxygen is released into the air, and breathed in by plants and animals during respiration. Plants perform a vital role in replenishing the oxygen level in the atmosphere. In photosynthesis, electrons are transferred from water to carbon dioxide in a reduction process. Chlorophyll assists in this process by trapping solar energy. When chlorophyll absorbs energy from sunlight, an electron in the chlorophyll molecule is excited from a lower to a higher energy state. The excited electron is more easily transferred to another molecule. A chain of electron-transfer steps follows, ending when an electron is transferred to a carbon dioxide molecule.

The original chlorophyll molecule is able to accept a new electron from another molecule. This ends a process that began with the removal of an electron from a water molecule. The oxidation-reduction reaction between carbon dioxide and water known as photosynthesis relies on the aid of chlorophyll. There are actually several types of chlorophyll, but all land plants contain chlorophyll a and b. These 2 types of chlorophyll are identical in composition apart from one side chain, composed of a -CH3 in chlorophyll a, while in chlorophyll b it is -CHO. Both consist of a very stable network of alternating single and double bonds, a structure that allows the orbitals to delocalize, making them excellent photoreceptors. The delocalised polyenes have very strong absorption bands in the visible light spectrum, making them ideal for the absorption of solar energy. The chlorophyll molecule is highly effective in absorbing sunlight, but in order to synthesize carbohydrates most efficiently, it needs to be attached to the backbone of a complex protein. This protein provides exactly the required orientation of the chlorophyll molecules, keeping them in the optimal position that enables them to react efficiently with nearby CO2 and H2O molecules.

This bacterial photoreceptor protein forms the backbone for a number of chlorophyll molecules. The basic structure seen in the chlorophyll molecule recurs in a number of molecules that assist in biochemical oxidation-reduction reactions, because it is ideally suited to promote electron transfer. Heme consists of a porphyrin similar to that in chlorophyll with an iron (II) ion at its center. Heme is bright red, the pigment that characterizes red blood. In the red blood cells of vertebrates, heme is bound to proteins to form hemoglobin. Oxygen enters the bloodstream in the lungs, gills or other respiratory surfaces and combines with hemoglobin. This oxygen is carried round the body of the organism in the bloodstream and released in the tissues. Hemoglobin in the muscle cells is known as myoglobin, a form that enables the organism to store oxygen as an electron source, ready for energy-releasing oxidation-reduction reactions. Commercial pigments Chlorophyll is a pigment that causes a green colour. Chlorophyll as a green dye has been used commercially in processed foods, toothpaste, soaps and cosmetics. Commercial pigments with structures similar to chlorophyll have been produced in a range of colors.

In some, the porphyrin is modified, for example by replacing the chlorine atoms with hydrogen atoms. In others, different metal ions may be present. Phthalocyanine is a popular bright blue pigment with a copper ion at the center of the porphyrin. Phthalocyanine is a blue pigment. Photosynthetic Pigments Photosynthetic Pigments Pigments are colorful compounds. Pigments are chemical compounds which reflect only certain wavelengths of visible light. This makes them appear "colorful". Flowers, corals, and even animal skin contain pigments which give them their colors. More important than their reflection of light is the ability of pigments to absorb certain wavelengths. Because they interact with light to absorb only certain wavelengths, pigments are useful to plants and other autotrophs --organisms which make their own food using photosynthesis. In plants , algae, and cyanobacteria , pigments are the means by which the energy of sunlight is captured for photosynthesis. However, since each pigment reacts with only a narrow range of the spectrum, there is usually a need to produce several kinds of pigments, each of a different color, to capture more of the sun's energy. There are three basic classes of pigments.

Chlorophylls are greenish pigments which contain a porphyrin ring. This is a stable ring-shaped molecule around which electrons are free to migrate. Because the electrons move freely, the ring has the potential to gain or lose electrons easily, and thus the potential to provide energized electrons to other molecules. This is the fundamental process by which chlorophyll "captures" the energy of sunlight. There are several kinds of chlorophyll, the most important being chlorophyll "a". This is the molecule which makes photosynthesis possible, by passing its energized electrons on to molecules which will manufacture sugars. All plants, algae, and cyanobacteria which photosynthesize contain chlorophyll "a". A second kind of chlorophyll is chlorophyll "b", which occurs only in "green algae" and in the plants . A third form of chlorophyll which is common is (not surprisingly) called chlorophyll "c", and is found only in the photosynthetic members of the Chromista as well as the dinoflagellates . The differences between the chlorophylls of these major groups was one of the first clues that they were not as closely related as previously thought.

Carotenoids are usually red, orange, or yellow pigments, and include the familiar compound carotene, which gives carrots their color. These compounds are composed of two small six-carbon rings connected by a "chain" of carbon atoms. As a result, they do not dissolve in water, and must be attached to membranes within the cell. Carotenoids cannot transfer sunlight energy directly to the photosynthetic pathway, but must pass their absorbed energy to chlorophyll. For this reason, they are called accessory pigments. One very visible accessory pigment is fucoxanthin the brown pigment which colors kelps and other brown algae as well as the diatoms . Phycobilins are water-soluble pigments, and are therefore found in the cytoplasm, or in the stroma of the chloroplast. They occur only in Cyanobacteria and Rhodophyta . The picture at the right shows the two classes of phycobilins which may be extracted from these "algae". The vial on the left contains the bluish pigment phycocyanin, which gives the Cyanobacteria their name.

The vial on the right contains the reddish pigment phycoerythrin, which gives the red algae their common name. Phycobilins are not only useful to the organisms which use them for soaking up light energy; they have also found use as research tools. Both pycocyanin and phycoerythrin fluoresce at a particular wavelength. That is, when they are exposed to strong light, they absorb the light energy, and release it by emitting light of a very narrow range of wavelengths. The light produced by this fluorescence is so distinctive and reliable, that phycobilins may be used as chemical "tags". The pigments are chemically bonded to antibodies, which are then put into a solution of cells. When the solution is sprayed as a stream of fine droplets past a laser and computer sensor, a machine can identify whether the cells in the droplets have been "tagged" by the antibodies. This has found extensive use in cancer research, for "tagging" tumor cells. Plant Pigments that absorb light Contact Us Plant Pigments Plants have different things in their cells that enable them to absorb light. The most common ones we find in the majority of plants are Chlorophyll A and Chlorophyll B.

Below we will briefly discuss the main pigments found in plant cells and relate them to the light spectrum. The light spectrum. Chlorophyll There are actually more than one kind of chlorophyll, but not all are present in all plants. In most plants they have at least Chlorophyll A and often chlorophyll B. Other Chlorophylls, which we won't discuss here, are: Chlorophyll cl, Chlorophyllc2, Chlorophyll d. Chlorophyll's are arranged in something called "photosystems" which are in the thylakoid membranes of chloroplasts. The main function of chlorophyll is to absorb light energy and transfer it to the reaction center chlorophyll of the photosystem. Chlorophyll a has an approximate absorption peak of 665 Nm and 465 Nm. Chlorophyll b has an approximate absorption peak of 640 Nm and 450 Nm. Accessory Pigments Accessory pigments are other pigments that are also able to absorb light.

Chlorophyll a & b are green and are able to best absorb light in the 450 nm (violet-blue) and 650 nm (red) area of the light spectrum. Well, that leaves (haha) the green, yellow and orange parts of the spectrum unusable. This is why plants have extra pigments (colours), in order to take in light from different wavelengths that chlorophyll is not good at absorbing. Carotene is an orange pigment capapble of photosynthesis. This pigment transmits light energy to chlorophyll. As well as photosynthesis, these pigments also help protect against too much light, photoinhibition. Phaeophytin a are gray-brown in colour. Phaeophytin b are yellow-brown. Xanthophyll are yellow pigments in the carotenoid group. These pigments seem to absorb best at 400-530nm. These are involved with photosynthesis with chlorophyll. Chlorophyll is often much more abundant than xanthophylls, and this is why the leaves are still a green colour.

When fall arrives in many countries and the leaves change colour, the chlorophyll "dies back" and the xanthophylls are more apparent in the yellow colour you see (like a maple tree) -The Xanthophyll cycle is a wondeful skill a plant has. In order to protect itself from absorbing too much light, and thus causing photoinhibition, Xanthophyll cycle converts pigments that do not quench energy into ones that do. When a plant recieves too much light, the xanthophyll cycle changes violoxanthin to antheraxanthin and zeaxanthin which are photoprotective pigments. Anthocyanin pigments are often red, purple or blue. These pigments have been said to help a plant against light stress and act to help protect a plant from blue-green and UV light. Cacti do not have these, they have Betalain instead. Betalain These pigments are found in Caryophyllales (cacti and beets for example). They are often a red-yellow-purple colour that is often found in flower colour, but it can also be found in leaves, stems, fruits and roots of these plants as well.

It is not really known what the exact purpose of these pigments are. -Betacyanins are reddish to violet Betalain pigments. They absorb light best at 535 nm. -Betaxanthins are yellow to orange Betalain pigments. They absorb light best at 480 nm. In relation to Photosynthesis It would seem, in my opinion, that given the various pigments, and the areas they are most abundant, that Chlorophyll a & b, and to a lesser extent, the various carotenoids (such as carotene and xanthophyll) would be the most productive in the absoprtion of light for photosynthesis. When applying this to cultivation and artificial lights, it would seem logical to choose lights that peak in the 430-470nm and 640-680nm range, to allow the 2 main chlorophyll types to gather the most energy. Light in the blue spectrum may also be a little stronger to allow the carotenes and xanthophylls to absorb more light as well.

Links Pigments for Photosynthesis Pigments for Photosynthesis Photosynthesis in plants is dependent upon capturing light energy in the pigment chlorophyll , and in particular chlorophyll a. This chlorophyll resides mostly in the chloroplasts and gives leaves their green color. The range of light absorption in leaves is extended by some accessory pigments such as the carotenoids , but does not cover the entire visible range - that would make the leaves black! Some plants and plantlike organisms have developed other pigments to compensate for low light or poor use of light. Cyanobacteria and red algae have phycocyanin and allophycocyanin as accessory pigments to absorbe orange light. They also have a red pigment called phycoerythrin that absorbs green light and extends the range of photosynthesis. The red pigment lycopene is found in vegetables. Some red algae are in fact nearly black, so that increases their photosynthetic efficiency. Brown algae have the pigment fucoxanthin in addition to chlorophyll to widen their absorption range. These red and brown algae grow to depths around 270 meters where the light is less than 1% of surface light.

But the most advanced plants are the land plants, which have the least advanced system for gathering light! Take a microscopic view. Chlorophylla-a is the primary pigment for photosynthesis in plants. Its structure is shown at left. It has the composition C55H72O5N4Mg. It exhibits a grass-green visual color and absorption peaks at 430nm and 662nm. It occurs in all photosynthetic organisms except photosynthetic bacteria. Chlorophyll-b has the composition C55H70O6N4Mg, the difference from chlorophyll-a being the replacement of a methyl group with a CHO. It exhibits a blue-green visual color and absorption peaks at 453nm and 642nm. It occurs in all plants, green algae and some prokaryotes. There is usually about half as much chlorophyll-b as the -a variety in plants. Photosynthetic Stages and Light-Absorbing Pigments - Molecular Cell Biology - NCBI Bookshelf Figure 16-34 The structure of a leaf and chloroplast.

The chloroplast is bounded by a double membrane: the outer membrane contains proteins that render it permeable to small molecules (MW < 6000); the inner membrane forms the permeability barrier (more...) Unlike mitochondria , chloroplasts contain a third membrane — the thylakoid membrane — that is the site of photosynthesis . In each chloroplast , the thylakoid membrane is believed to constitute a single, interconnected sheet that forms numerous small flattened vesicles, the thylakoids , which commonly are arranged in stacks termed grana (see Figure 16-34 ). The spaces within all the thylakoids constitute a single continuous compartment, the thylakoid lumen. The thylakoid membrane contains a number of integral membrane proteins to which are bound several important prosthetic groups and light-absorbing pigments, most notably chlorophyll. Carbohydrate synthesis occurs in the stroma, the soluble phase between the thylakoid membrane and the inner membrane. In photosynthetic bacteria extensive invaginations of the plasma membrane form a set of internal membranes, also termed thylakoid membranes, or simply thylakoids, where photosynthesis occurs.

Three of the Four Stages in Photosynthesis Occur Only during Illumination It is convenient to divide the photosynthetic process in plants into four stages, each occurring in a defined area of the chloroplast : (1) absorption of light, (2) electron transport leading to the reduction of NADP+ to NADPH, (3) generation of ATP, and (4) conversion of CO2 into carbohydrates ( carbon fixation ). All four stages of photosynthesis are tightly coupled and controlled so as to produce the amount of carbohydrate required by the plant. All the reactions in stages 1 – 3 are catalyzed by proteins in the thylakoid membrane . The enzymes that incorporate CO2 into chemical intermediates and then convert it to starch are soluble constituents of the chloroplast stroma (see Figure 16-34 ). The enzymes that form sucrose from three-carbon intermediates are in the cytosol . Absorption of Light The initial step in photosynthesis is the absorption of light by chlorophylls attached to proteins in the thylakoid membranes.

Like cytochromes , chlorophylls consist of a porphyrin ring attached to a long hydrocarbon side chain ( Figure 16-35 ). They differ from cytochromes (and heme) in containing a central Mg2+ ion (rather than Fe atom) and having an additional five-membered ring. The energy of the absorbed light is used to remove electrons from an unwilling donor (water, in green plants), forming oxygen, and then to transfer the electrons to a primary electron acceptor, a quinone designated Q, which is similar to CoQ. Figure 16-36 The structure of β-carotene, a pigment that assists in light absorption by chloroplasts. β-Carotene, which is related to the visual pigment retinal (see Figure 21-47), is one of a family of carotenoids containing long hydrocarbon chains (more...) One of the strongest pieces of evidence for the involvement of chlorophylls and β-carotene in photosynthesis is that the absorption spectrum of these pigments is similar to the action spectrum of photosynthesis ( Figure 16-37 ).

The latter is a measure of the relative ability of light of different wavelengths to support photosynthesis. Figure 16-37 Photosynthesis at different wavelengths. (a) The action spectrum of photosynthesis in plants; that is, the ability of light of different wavelengths to support photosynthesis. (b) The absorption spectra for three photosynthetic pigments: chlorophyll (more...) When chlorophyll a (or any other molecule) absorbs visible light, the absorbed light energy raises the chlorophyll a to a higher energy state, termed an excited state. This differs from the ground (unexcited) state largely in the distribution of electrons around the C and N atoms of the porphyrin ring (see Figure 16-35 ). Excited states are unstable, and will return to the ground state by one of several competing processes. For chlorophyll a molecules dissolved in organic solvents, such as ethanol, the principal reactions that dissipate the excited-state energy are the emission of light (fluorescence and phosphorescence) and thermal emission (heat). The situation is quite different when the same chlorophyll a is bound to the unique protein environment of the reaction center.

Light Absorption by Reaction-Center Chlorophylls Causes a Charge Separation across the Thylakoid Membrane The absorption of a quantum of light of wavelength ≈680 nm causes a chlorophyll a molecule to enter the first excited state. The energy of such photons increases the energy of chlorophyll a by 42 kcal/mol. In the reaction center, this excited-state energy is used to promote a charge separation across the thylakoid membrane : an electron is transported from a chlorophyll molecule to the primary electron acceptor, the quinone Q, on the stromal surface of the membrane, leaving a positive charge on the chlorophyll close to the luminal surface ( Figure 16-38 ). The reduced primary electron acceptor becomes a powerful reducing agent, with a strong tendency to transfer the electron to another molecule. The positively charged chlorophyll, a strong oxidizing agent, will attract an electron from an electron donor on the luminal surface. These potent biological reductants and oxidants provide all the energy needed to drive all subsequent reactions of photosynthesis : electron transport , ATP synthesis, and CO2 fixation. Figure 16-38 The primary event in photosynthesis.

After a photon of light of wavelength ≈680 nm is absorbed by one of the many chlorophyll molecules in one of the light-harvesting complexes (LHCs) of an antenna (only one is shown), some of the absorbed energy (more...) The significant features of the primary reactions of photosynthesis are summarized in the following model, in which P represents the chlorophyll a in the reaction center, and Q represents the primary electron acceptor: According to this model, the ground state of the reaction-center chlorophyll, P, is not a strong enough reductant to reduce Q; that is, an electron will not move spontaneously from P to Q. However, the excited state of the reactioncenter chlorophyll, P*, is an excellent reductant and rapidly (in about 10−10 seconds) donates an electron to Q, generating P+ and Q−. This photochemical electron movement, which depends on the unique environment of both the chlorophylls and the acceptor within the reaction center, occurs nearly every time a photon is absorbed. The acceptor, Q−, is a powerful reducing agent capable of transferring the electron to still other molecules, ultimately to NADP+.

The powerful oxidant P+ can remove electrons from other molecules to regenerate the original P. In plants, the oxidizing power of four molecules of P+ is used, by way of intermediates, to remove four electrons from H2O to form O2: Chlorophyll a also absorbs light at discrete wavelengths shorter than 680 nm (see Figure 16-37b ). Such absorption raises the molecule into one of several higher excited states, which decay within 10−12 seconds (1 picosecond, ps) to the first excited state P*, with loss of the extra energy as heat. Photochemical charge separation occurs only from the first excited state of the reaction-center chlorophyll a, P*. This means that the quantum yield — the amount of photosynthesis per absorbed photon — is the same for all wavelengths of visible light shorter than 680 nm. The chlorophyll a molecules within reaction centers are capable of directly absorbing light and initiating photosynthesis .

However, even at the maximum light intensity encountered by photosynthetic organisms (tropical noontime sun, ≈1.2 × 1020 photons/m2/s), each reaction-center chlorophyll a absorbs about one photon per second, which is not enough to support photosynthesis sufficient for the needs of the plant. To increase the efficiency of photosynthesis, especially at more typical light intensities, organisms utilize additional light-absorbing pigments. Light-Harvesting Complexes Increase the Efficiency of Photosynthesis As noted earlier, each reaction center is associated with an antenna, which contains several light-harvesting complexes (LHCs), packed with chlorophyll a and, depending on the species, chlorophyll b and other pigments. LHCs promote photosynthesis by increasing absorption of 680-nm light and by extending the range of wavelengths of light that can be absorbed (see Figure 16-37 ). Photons can be absorbed by any of the pigment molecules in each LHC.

The absorbed energy is then rapidly transferred (in <10−9 seconds) to one of the two chlorophyll a molecules in the associated reaction center, where it promotes the primary photosynthetic charge separation (see Figure 16-38 ). Within an LHC are several transmembrane proteins whose role is to maintain the pigment molecules in the precise orientation and position that are optimal for light absorption and energy transfer, thereby maximizing the very rapid and efficient process known as resonance transfer of energy from antenna pigments to reaction-center chlorophylls . As depicted in Figure 16-39a , some photosynthetic bacteria contain two types of LHCs: the larger type (LH1) is intimately associated with a reaction center; the smaller type (LH2) can transfer absorbed light energy to an LH1. Figure 16-39b shows the structure of the subunits that make up the LH2 complex in Rhodopseudomonas acidophila. Surprisingly, the molecular structures of plant light-harvesting complexes are completely different from those in bacteria, even though both types contain carotenoids and chlorophylls in a clustered geometric arrangement within the membrane .

UCSB Science Line UCSB Science Line At which wavelength does maximum Photosynthesis take place? Answer 1: Photosynthesis is the ability of plants to absorb the energy of light, and convert it into energy for the plant. To do this, plants have pigment molecules which absorb the energy of light very well. The pigment responsible for most light-harvesting by plants is chlorophyll, a green pigment. The green color indicates that it is absorbing all the non-green light-- the blues (~425-450 nm), the reds and yellows (600-700 nm). Red and yellow light is longer wavelength, lower energy light, while the blue light is higher energy. In between the two is green light (~500-550 nm). It seems strange that plants would harvest the lower energy red light instead of the higher energy green light, unless you consider that, like all life, plants first evolved in the ocean. Sea water quickly absorbs the high-energy blue and green light, so that only the lower energy, longer wavelength red light can penetrate into the ocean.

Since early plants and still most plant-life today, lived in the ocean, optimizing their pigments to absorb the reds and yellows that were present in ocean water was most effective. While the ability to capture the highest energy blue light was retained, the inability to harvest green light appears to be a consequence of the need to be able to absorb the lower energy of red light. Plants also use multiple variants of chlorophyll, as well as accessory pigments such as carotenoids (which give carrots their orange color) to tune themselves to absorbing different wavelengths of light. That makes it impossible to assign a single wavelength of best absorption for all plants. All plants, however, has chlorophyll a, which absorbs most strongly at ~450 nm, or a bright blue color. This wavelength is strong in natural sunlight, and somewhat present in incandescent lights, but is very weak in traditional fluorescent lights. Special plant lights increase the amount of light of this wavelength that they produce. But a 400-500 nm wavelength bulb wouldn't be enough, since many plants take cues for germination, flowering, and growth from the presence of red light as well.

Good plant lights produce red light as well, giving plants all the wavelengths of light they need for proper growth. Note from ScienceLine Moderator Below is a correction to a paragraph on this answer sent to the ScienceLine site on June 12th, 2013: Paragraph"Sea water quickly absorbs the high-energy blue and green light, so that only the lower energy, longer wavelength red light can penetrate into the ocean. Since early plants and still most plant-life today, lived in the ocean, optimizing their pigments to absorb the reds and yellows that were present in ocean water was most effective.' Correction: In fact, red light gets absorbed by the ocean most quickly, and it is only blue light which can penetrate to any depth. Answer 2: In reference to the answer above: "It seems strange that plants would harvest the lower energy red light instead of the higher energy green light, unless you consider that, like all life, plants first evolved in the ocean.

Sea water quickly absorbs the high-energy blue and green light, so that only the lower energy, longer wavelength red light can penetrate into the ocean." The exact opposite actually it true, blue light with the short wavelength colors such as blue actually penetrating the deepest, while long wavelength colors such red light penetrates the shallowest. Not to mention that in coastal waters green light is actually the spectrum that penetrates deepest.... oceanexplorer Answer 3: I think the graphic from NASA on Answer #1 above, makes it pretty clear that short wavelengths penetrate deeper. H2O liquid must have some red and infra red absorption bands. Not to mention the particulate debris in water Since the particles' sizes are of much bigger wavelength than EM, the red wavelengths will be more scattered than the blue, so that also will not favor transmission of the redish photons. Click Here to return to the search form. Copyright © 2015 The Regents of the University of California, All Rights Reserved. UCSB Science Line UCSB Science Line Why is the chlorophyll in plants green or even red, orange, or brown?

Answer 1: The purpose of photosynthesis is to convert the energy in photons (the infinitesimally small packets of energy that make up light) into the chemical bonds of sugar molecules. Plants (and animals that eat plants) can then store the energy and get it back out when they need it by breaking those chemical bonds. The tricky part of photosynthesis is that it takes a very precise amount of energy to form a particular chemical bond. Furthermore, the photons from different colors of light contain different amounts of energy. You probably know the colors of the spectrum (Red, Orange, Yellow, Green, Blue, Indigo, Violet); well, those colors are in ascending order of energy -- a photon of blue light has more energy than a photon of red light (this is true because of Planck's Law, which a physicist could explain better than I). A particular pigment molecule (like chlorophyll) is specialized for absorbing a particular color of light and converting the light energy into the appropriate amount of chemical energy for making a chemical bond (actually there are many other molecules that help the pigment perform this energy conversion, but only the pigment itself can absorb the light).

Chlorophyll just absorbs blue and red light; it hardly absorbs any green light at all, so the green gets reflected back to our eyes, which is why leaves appear green. Other pigments that plants have in their leaves absorb light of different colors, so they reflect red, orange, yellow, or blue light and appear to be those colors to our eyes. Because the white light coming from the sun is actually made up of photons of all the different colors, it is very advantageous to the plant to have many pigments that can absorb such a wide range of the available colors of light. Answer 2: Chlorophyll is a green pigment that gives most plants their color.The reason that it is green is because it absorbs other colors of light such as red and blue, so in a way the green light is reflected out since the pigment does not absorb it. Plants contain other pigments that reflect different colors, but these are often masked by Chlorophyll. An example of another common pigment is the carotenoids. During autumn, when the days begin to shorten, the amount of chlorophyll in the leaves of trees is dramatically reduced.

This is when the colors of the carotenoids become more prevalent and is what you see when the leaves appear to change color. Answer 3: Different photosynthetic organisms use different combinations of pigments, which have different colors because they absorb and reflect different frequencies of light. Plants and green algae (plants are really advanced green algae) contain chlorophyll a (which is teal-green), chlorophyll b (which is yellow-green), and beta-carotene (which is yellow), thus giving them a green color. Brown algae and their unicellular relatives (e.g. diatoms) have chlorophyll a,chlorophyll c, and lipid pigments called fucoxanthins,which together give them a golden-brown color. Red algae possess chlorophyll a and lipid-based pigments called phycobilins, which give them the brilliant red(or deep blue) color. These different combinations of pigments are more or less efficient at collecting light at certain frequencies and at certain levels of light intensity (too much will damage the pigment). Thus, they parcel out the Sun's energy to make the most use of it and to not compete with other photosynthetic organisms. Answer 4: I'm a little confused about your question.

Chlorophyll pigment is always green. Plant leaves and stems aren't always green because they have many pigments other than chlorophyll. Pigments are molecules that absorb specific colors of light and reflect other colors, depending on their chemical structure. The reflected colors are what give pigments their color. Chlorophyll pigments are green because they reflect green light. There are different types of chlorophyll (chlorophyll-a, chlorophyll-b, chlorophyll-c1, chlorophyll-c2, chlorophyll-d, divinyl chlorophyll-a). These different types of chlorophyll are the same basic molecule with very slight differences in their chemical structures. Because the different chlorophylls have the same basic structure, they all reflect green light and so appear green, but their small structural differences cause them to be different shades of green (yellow-green, lime green, forest green, blue-green, etc.). To see the structure of chlorophyll, go to click here Land plants (and plants in the ocean, called algae) have a lot of chlorophyll-a pigment because it is essential to photosynthesis, but they also have other pigments, called accessory pigments, that help them absorb light.

These accessory pigments can be other chlorophylls or they can be completely different pigments with completely different colors, including yellow (xanthophylls), orange (carotenes), red and purple (phycobilins) or brown and gray (phaeophytin). Most land plants are green (their stems and leaves, anyway) because the accessory pigments are chlorophylls, including chlorophyll-b and chlorophyll-c. When green leaves "turn colors" in the fall, or turn yellow due to nutrient limitation or disease, the chlorophylls are breaking down and being re-absorbed, allowing the other pigments to show through. If you've even been scuba diving or snorkeling, you may have noticed that only some algae in the ocean are green and that most are brown, red, purple, yellow or even iridescent blue. The study of land plants is called botany and the study of algae is called phycology. I myself am a phycologist because I study marine algae. To read more about photosynthetic pigment, including chlorophyll, go to click here Click Here to return to the search form.

Copyright © 2015 The Regents of the University of California, All Rights Reserved. What is the main energy trapping molecule in plants? | Reference.com What is the main energy trapping molecule in plants? A: Quick Answer Chlorophyll, which is a green pigment, is the main molecule that traps energy in plants. Chlorophyll is found in the chloroplasts of plant cells. Through the photosynthesis process, chloroplasts absorb the sun's energy through the chlorophyll molecules in order to make food. Full Answer Other structures associated with the chloroplasts are the inner and outer membranes, stroma and thylakoids. Inside the chloroplast is a liquid called the stroma in which the thylakoid float. The thylakoids are the compartments that contain the chlorophyll. Photosynthesis involves the capture of light energy by the chlorophyll which in turn keeps it in the molecule adenosine triphosphate, or ATP. This molecule combined with the reactants carbon dioxide and water produce sugar and oxygen. Absorption of Light About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made.

Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account. There, you can easily access this resource later when you’re ready to customize it or assign it to your students. Absorption of Light Pigments, like chlorophyll and carotenoids, absorb and reflect light at a certain region of the electromagnetic spectrum. Learning Objective Differentiate between chlorophyll and carotenoids. Key Points Plant pigment molecules absorb only light in the wavelength range of 700 nm to 400 nm; this range is referred to as photosynthetically-active radiation. Violet and blue have the shortest wavelengths and the most energy , whereas red has the longest wavelengths and carries the least amount of energy. Pigments reflect or transmit the wavelengths they cannot absorb, making them appear in the corresponding color. Chorophylls and carotenoids are the major pigments in plants; while there are dozens of carotenoids, there are only five important chorophylls: a, b, c, d, and bacteriochlorophyll.

Chlorophyll a absorbs light in the blue-violet region, chlorophyll b absorbs red-blue light, and both a and b reflect green light (which is why chlorophyll appears green). Carotenoids absorb light in the blue-green and violet region and reflect the longer yellow, red, and orange wavelengths; these pigments also dispose excess energy out of the cell . Terms Full Text Absorption of Light Light energy initiates the process of photosynthesis when pigments absorb the light. Organic pigments have a narrow range of energy levels that they can absorb. Energy levels lower than those represented by red light are insufficient to raise an orbital electron to an excited, or quantum, state. Energy levels higher than those in blue light will physically tear the molecules apart, a process called bleaching. For example, retinal pigments can only "see" (absorb) 700 nm to 400 nm light; this is visible light . For the same reasons, plant pigment molecules absorb only light in the wavelength range of 700 nm to 400 nm; plant physiologists refer to this range for plants as photosynthetically-active radiation.

The visible light seen by humans as the color white light actually exists in a rainbow of colors in the electromagnetic spectrum , with violet and blue having shorter wavelengths and, thus, higher energy. At the other end of the spectrum, toward red, the wavelengths are longer and have lower energy . The colors of visible light do not carry the same amount of energy. Violet has the shortest wavelength and, therefore, carries the most energy, whereas red has the longest wavelength and carries the least amount of energy. Understanding Pigments Different kinds of pigments exist, each of which has evolved to absorb only certain wavelengths or colors of visible light. Pigments reflect or transmit the wavelengths they cannot absorb, making them appear in the corresponding color. Chlorophylls and carotenoids are the two major classes of photosynthetic pigments found in plants and algae; each class has multiple types of pigment molecules. There are five major chlorophylls: a, b, c and d, along with a related molecule found in prokaryotes called bacteriochlorophyll. With dozens of different forms, carotenoids are a much larger group of pigments.

The carotenoids found in fruit , such as the red of tomato (lycopene), the yellow of corn seeds (zeaxanthin), or the orange of an orange peel (β-carotene), are used to attract seed-dispersing organisms. In photosynthesis, carotenoids function as photosynthetic pigments that are very efficient molecules for the disposal of excess energy. When a leaf is exposed to full sun, the light-dependent reactions are required to process an enormous amount of energy; if that energy is not handled properly, it can do significant damage. Therefore, many carotenoids are stored in the thylakoid membrane to absorb excess energy and safely release that energy as heat. Each type of pigment can be identified by the specific pattern of wavelengths it absorbs from visible light, which is the absorption spectrum. Chlorophyll a absorbs light in the blue-violet region, while chlorophyll b absorbs red-blue light. Neither a or b absorb green light; because green is reflected or transmitted, chlorophyll appears green. Carotenoids absorb light in the blue-green and violet region and reflect the longer yellow, red, and orange wavelengths .

(a) Chlorophyll a, (b) chlorophyll b, and (c) β-carotene are hydrophobic organic pigments found in the thylakoid membrane. Chlorophyll a and b, which are identical except for the part indicated in the red box, are responsible for the green color of leaves. β-carotene is responsible for the orange color in carrots. Each pigment has (d) a unique absorbance spectrum. Many photosynthetic organisms have a mixture of pigments. In this way organisms can absorb energy from a wider range of wavelengths. Not all photosynthetic organisms have full access to sunlight. Some organisms grow underwater where light intensity and quality decrease and change with depth. Other organisms grow in competition for light. Plants on the rainforest floor must be able to absorb any light that comes through because the taller trees absorb most of the sunlight and scatter the remaining solar radiation Plants that commonly grow in the shade have adapted to low levels of light by changing the relative concentrations of their chlorophyll pigments. When studying a photosynthetic organism, scientists can determine the types of pigments present by using a spectrophotometer . These instruments can differentiate which wavelengths of light a substance can absorb.

Spectrophotometers measure transmitted light and compute its absorption. By extracting pigments from leaves and placing these samples into a spectrophotometer, scientists can identify which wavelengths of light an organism can absorb.

Question: What is the green pigment found in most plants that is responsible for absorbing light energy?
Answer: Chlorophyll