Examine the molecular structure of representative chlorophyll and carotenoid molecules in Figures: Structure A and B. Notice the linear system of conjugated double bonds in the carotenoid lutein and the zig-zag of conjugated double bonds in the large ring structure of the chlorophyll.
These systems of conjugated double bonds are responsible for the ability to absorb light energy from photons. Photosynthetic Pigments A pigment is a generic term for a molecule that absorbs light and has a color. Previous Page Next Page. More complicated diagrams will be displayed to illustrate the structures of the three types of pigments that are present during the aging of leaves: chlorophylls , carotenoids , and anthocyanins. Carotenoids are very long-chain water-repelling pigments that are synthesized in the plastids of plant cells.
These pigments primarily absorb in the blue wavelengths, allowing the longer wavelengths to be scattered and producing the yellow color. In autumn foliage, the carotenoids are left over in the chloroplasts and revealed from the loss of chlorophyll.
The chlorophylls, a and b, are the pigments of photosynthesis. They are produced in chloroplasts in the photosynthetic tissues of the leaf.
The chlorophyll molecules are very water repelling, partly because of the long phytol tail in the molecule. The closed ring of the molecule is similar to the hemoglobin of our blood, but holds a magnesium ion rather than iron. It is a large and expensive molecule to make, partly because each ring contains four nitrogen atoms. Chlorophyll is normally broken down towards the end of the leaf life span, and much of the nitrogen is resorbed by the plant.
Present in certain teas, wine, and chocolate Yellow, red, blue, purple Betalains Betacyanins and betaxanthins Flowers and fungi Red to violet, also yellow to orange. Chlorophyll is green, and is responsible for the green color of foliage and leaves.
More importantly, by enabling plants to produce oxygen during photosynthesis, it is critical to sustaining our life on earth. Chlorophyll has structural features similar to heme. Bilirubin, which produces a yellow color, has recently been found in plants. Red, orange, and yellow plants, as well as other organisms, generally rely on carotenoids for their vivid colors. Carotene is a pigment that absorbs blue and indigo light, and that provides rich yellows and oranges.
The distinctive colors of mango, carrots, fall leaves, and yams are due to various forms of carotene, as is the yellow of butter and other animal fats. This pigment is important to our diet, as the human body breaks down each carotene molecule to produce two vitamin A molecules. Lycopene, canthaxanthin, and astaxanthin share a similar structure to carotene.
The red tones of tomatoes, guava, red grapefruit, papaya, rosehips, and watermelon indicate the presence of lycopene. Canthaxanthin produces the pink colors of flamingos , some crustaceans, salmon, and trout. In its synthetic form, it is used to ensure captive flamingos retain their coloring, as a red food colorant, and even as a tanning aid. Astaxanthin provides the red colors of cooked salmon, red bream, trout, lobster, and shellfish.
In a live animal, astaxanthin is combined with a protein and is blackish in color. Flavonoids are the yellow plant pigments seen most notably in lemons, oranges, and grapefruit. The name stems from the Latin word "flavus," which means yellow. Flavonoids in flowers and fruit provide visual cues for animal pollinators and seed dispersers to locate their targets.
Flavonoids are located in the cytoplasm and plastids. Many of the foods that we eat, including dark chocolate, strawberries, blueberries, cinnamon, pecans, walnuts, grapes, and cabbage, contain flavonoids. These chemicals lower cholesterol levels, and many have antioxidant properties.
0コメント