Wavelengths of light and photosynthetic pigments (article) | Khan Academy
Pigments are "molecules that absorb specific wavelengths (energies) of light and reflect all others." Chlorophyll a: This is the most abundant pigment in plants. The most important function of carotenoids seems to be protecting the plant. We have obtained an action spectrum for chlorophyll formation in Euglena gracilis. This action spectrum is similar to the absorption spectrum of protochlorophyll. Oct 15, Some carotenoids are converted by the body to vitamin A, which is system benefits and are sometimes associated with cardiovascular disease prevention. The difference between the two groups is chemical: xanthophylls.
- The Difference between Chlorophyll A & B and Photosynthesis Overview
- THE RELATIONSHIP BETWEEN CHLOROPHYLL AND THE CAROTENOIDS IN THE ALGAL FLAGELLATE, EUGLENA
- The role of carotenoids in human health.
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. The set of wavelengths absorbed by a pigment is its absorption spectrum. In the diagram below, you can see the absorption spectra of three key pigments in photosynthesis: The set of wavelengths that a pigment doesn't absorb are reflected, and the reflected light is what we see as color.
For instance, plants appear green to us because they contain many chlorophyll a and b molecules, which reflect green light. Each photosynthetic pigment has a set of wavelength that it absorbs, called an absorption spectrum. Absorption spectra can be depicted by wavelength nm on the x-axis and the degree of light absorption on the y-axis.
Light and photosynthetic pigments
The absorption spectrum of chlorophylls includes wavelengths of blue and orange-red light, as is indicated by their peaks around nm and around nm. As a note, chlorophyll a absorbs slightly different wavelengths than chlorophyll b. Chlorophylls do not absorb wavelengths of green and yellow, which is indicated by a very low degree of light absorption from about to nm.
Optimal absorption of light occurs at different wavelengths for different pigments. Image modified from " The light-dependent reactions of photosynthesis: Here, we'll look at two groups of pigments that are important in plants: Chlorophylls There are five main types of chlorophylls: In plants, chlorophyll a and chlorophyll b are the main photosynthetic pigments. Chlorophyll molecules absorb blue and red wavelengths, as shown by the peaks in the absorption spectra above.
In addition to these enzymes produced by the body, antioxidant nutrients taken into the body through foods or through dietary supplements also can surrender electrons to the free radicals without adding to the chain reactionthus terminating the free radical reactions. Antioxidant nutrients include vitamins A, C, and E, bioflavonoidslipoic acidand carotenoids. Despite the large number of carotenoids in nature, only about 50 are present in foods that people in the United States eat, and only about 14 of those have been identified in blood, an indication of what is absorbed in the human body.
All carotenoids are fat-soluble compounds, meaning that they can dissolve in fats and oils, but not in water. The carotenoid family consists of smaller families of pigments called carotenes and xanthophylls. Carotenes are hydrocarbons, containing only carbon and hydrogen atoms, while xanthophylls also contain oxygen.
The carotenes have been studied more than the other carotenoids. The ones of most interest in human nutrition are beta-carotene, alpha-carotene, and lycopene. Important xanthophylls include luteinastaxanthin, zeaxanthin, and cryptoxanthin. As acceptance of the many health benefits of carotenoids increases and continues to be proven, the addition of five individual carotenoids alpha-carotene, beta-carotene, lutein, lycopene, and beta-cryptoxanthin were added to the National Cancer Institute's Diet History Questionnaire.
The carotenoids appear to have many health benefits, but more research is required to confirm many of the health effects seen so far and to identify additional benefits. As one of the most common carotenoids, beta-carotene is the most well-known and well-studied carotenoid. It is found in carrots, pumpkins, peaches, and sweet potatoes. Beta-carotene is the primary precursor to vitamin A. With the aid of dioxygenase enzymes, the human body can split one molecule of beta-carotene into two vitamin A molecules.
Vitamin A has many vital functions in the human body, including being involved in: Vitamin A deficiency symptoms include night blindnessdry eyes, dry, rough skin, impaired bone growth, and susceptibility to respiratory infections. Vitamin A, is a fat soluble vitamin, can be stored in the body long-term and can reach toxic levels over time if amounts above recommended levels 10, IU for adults and only 6, IU for pregnant women are ingested.
Carotenoids | elecciones2013.info
Too much vitamin A can cause headaches, vision problems, nausea, vomitingan enlarged liver or spleen, birth defectsand even death at very high levels. Beta-carotene is a better source of vitamin A than vitamin A supplements because it is only converted to vitamin A on an as-needed basis; excess beta-carotene is stored in the body and unlike vitamin A, is not toxic when taken in amounts in excess of body needs.
Beta-carotene also improves immune function, increases lung capacity, reduces DNA damage, may provide protection from the sun, and may lessen the risks of some types of cancer. However, for people who drink and smoke excessively, beta-carotene may increase their risk of lung cancer. Alpha-carotene, another common carotenoid, is normally found in the same foods as beta-carotene. It is similar to beta-carotene in structure, with one of the ring structures being beta-ionone.
However, the other ring is different, so one molecule of alpha-carotene yields only one molecule of vitamin A. Alpha-carotene has been found to have powerful anticancer properties in cell-culture studies.
Lycopene is often the most common carotenoid in the American diet because it is found in tomato products, including pizza and spaghetti sauce. It is also present in lesser amounts in watermelon, pink grapefruit, guava, and apricots. Lycopene does not produce vitamin A. However, lycopene in tomato juice and spaghetti and pizza sauces has been associated with a lower risk of prostate cancer in men. In latethe first clinical trial showed that lycopene supplementation could even slow progression of prostate cancer growths.
Cooked tomato sauces were to found to be associated with greater health benefits, compared to uncooked tomatoes, because the lycopene in the cooked tomatoes was more easily absorbed. Also, since lycopene is fat-soluble, absorption increased when it was mixed with oil in the sauces.
Uncooked tomatoes also demonstrated health benefits, though to a lesser degree, especially when they were used in a salad with a oil-based dressing or in a sandwich with fat-containing meat.
Lycopene may help in the prevention of other cancers as well as protect against heart attacks. A study late in indicated that lycopene may also help patients with exercise-induced asthma. Research is continuing on the potential health benefits of lycopene. Lutein, which is almost as common as beta-carotene in the American diet, and zeaxanthin are xanthophylls found in kale, spinach, broccoli, corn, alfalfaand egg yolks.
Both are components of the macula of the eye, a small area in the center of the retina responsible for detailed vision. These carotenoids may prevent and slow macular degenerationa leading cause of blindness in the elderly.