Question

Natural chlorophyll is apparently one of the least stable forms of chlorophyll. But what is the distribution of metals in the earth’s crust? Does the chlorophyll molecule need to be very stable in order to function properly?

Answer 1

Mg (2.33%) Na (2.36%) Ca (4.15%) Fe (5.63%) (K (2.09%) Ti (0.57%) H 0.14%) Al (8.32%) Oxygen Silicon Aluminum Iron Calcium - Sodium - Magnesium Potassium Oxygen (46.4%) Most common elements in the crust Silicon (28.2%)

Chlorophyll molecules are magnesium-tetrapyrrole pigments that give plants, algae, and cyanobacteria their characteristic green color, and are the primary pigments used in plant photosynthesis. Chlorophyll molecules facilitate the conversion of absorbed solar radiation into stored chemical energy, through harvesting light energy, transferring excitation energy to reaction centers, and driving charge separation in the reaction centers. There are five different types of chlorophyll molecules that are naturally present in photosynthetic organisms: Chlorophyll a, b, c, d, and f. All of the chlorophyll molecules have similar chemical structures, which are characterized by a chlorin ring with a central magnesium ion, and small variations in five-membered ring structures or side chains. The small differences in the chemical structures of the chlorophyll molecules cause variations in their light absorption properties and allow photosynthetic organisms to harvest sunlight at different wavelengths, in order to maximize the light energy available for photosynthesis. The free electrons at the molecular level in the chemical structure of these photosynthetic pigments revolve at certain energy levels. When light energy (photons of light) falls on these pigments, the electrons absorb this energy and jump to the next energy level. They cannot continue to stay in that energy level, as it is not the state of stability for these electrons, so they must dissipate this energy and come back to their stable energy level. During photosynthesis these high-energy electrons transfer their energy to other molecules, or these electrons themselves get transferred to other molecules. Hence, they release the energy they had captured from light. This energy is then used by other molecules to form sugar and other nutrients by using carbon dioxide and water.

In an ideal situation the pigments must be capable of absorbing light energy of the entire wavelength, so that the maximum energy can be absorbed. To do so, they should appear black, but chlorophylls are actually green or brown in color and absorb light wavelengths in the visible spectrum. If the pigment starts absorbing wavelength away from the visible light spectrum, such as ultraviolet or infrared rays, the free electrons may gain so much energy that they will either get knocked off their orbit or may soon dissipate energy in the form of heat, thus damaging the pigment molecules. So it is the visible wavelength energy absorbing capability of pigment that is important for photosynthesis to take place.