Chlorophyll (from English, chlorophyll) or leaf chlorophyll (direct translation from the Dutch, bladgroen) is a pigment that is owned by a variety of organisms and is one molecule plays a key role in photosynthesis. Chlorophyll gives the green color in the leaves of green plants and green algae, but also shared by many other algae, and some groups of photosynthetic bacteria. Chlorophyll molecule absorbs red light, blue, and purple, and green reflective and a little yellow, so that the human eye receives color. In land plants and green algae, chlorophyll is produced and isolated plastids called chloroplasts.

Chlorophyll has several forms. Chlorophyll-a found in all organisms autotrophs. Chlorophyll-b owned green algae and land plants. Chlorophyll-c algae possessed blond, golden algae and diatoms (Bacillariophyta). Chlorophyll-d owned by red algae (Rhodophyta). Besides different chemical formula, the types of chlorophyll is also different wavelengths of light are absorbed.

Though varied, all the chlorophyll has a chemical structure alike, which is composed of porphyrin closed (cyclic), a tetrapirol, with a magnesium ion at its center and the "tail" terpenes. Both of these groups is the chromophore ("color bearer") and capable excited electrons when exposed to light at specific wavelengths. Because of the role of chlorophyll, land plants can make their own food with the help of sunlight so be autotrophs organisms.

1. Chlorophyll and photosynthesis

Chlorophyll and photosynthesis is something that is very related because chlorophyll is essential for photosynthesis, which allows plants to absorb energy from light. Chlorophyll molecules are specifically arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts. In this section, chlorophyll has two main functions. The function of the majority of chlorophyll (up to several hundred molecules per photosystem) is to absorb light and transfer light energy through resonance energy transfer to a specific chlorophyll pair in the reaction center of photosystem.

Both currently accepted photosystem units of photosystem II and photosystem I, which has its own chlorophyll a different reaction center, named P680 and P700, respectively. These pigments are named after the wavelength (in nanometers) red-peak absorption maximum of them. The nature of identity, and the spectral function of the type of chlorophyll in each photosystem are distinct and determined by each other and the protein structure surrounding them. Once extracted from the protein into the solvent (such as acetone or methanol).

The function of the reaction center chlorophyll is to use the energy that is absorbed by and transferred to it from other chlorophyll pigments in photosystems to undergo a charge separation, a specific redox reaction in which the chlorophyll donates an electron into a series of intermediate molecules called the electron transport chain. Charged reaction center chlorophyll (P680 +) which is then reduced back to the ground state by accepting electrons. In Photosystem II, the electron which reduces P680 + ultimately comes from the oxidation of water into O2 and H + through several intermediates. This reaction is how photosynthetic organisms such as plants produce O2 gas, and is the source for almost all the O2 in Earth's atmosphere. Photosystem I usually work in series with Photosystem II, so the P700 + of Photosystem I is usually reduced, via many intermediates in the thylakoid membrane, by electrons ultimately from Photosystem II. Electron transfer reactions in the thylakoid membrane complex, however, and the source of electrons used to reduce P700 + can vary.

The flow of electrons produced by the reaction center chlorophyll pigments is used to shuttle H + ions across the thylakoid membrane, setting up a chemiosmotic potential is used mainly to produce ATP chemical energy, and the electrons ultimately reduce NADP + to NADPH, a universal reductant used to reduce CO2 into sugars and other biosynthetic reductions.

The reaction center chlorophyll-protein complex capable of directly absorbing light and do activities without charge separation other chlorophyll pigments, but the absorption cross section (possibly absorbing a photon under a given light intensity) is small. Thus, the remaining chlorophyll in the photosystem and pigment-protein antenna complexes associated with the photosystems all cooperatively absorb and funnel light energy to the reaction center. In addition to chlorophyll, there are other pigments, called accessory pigments, which occur in the antenna pigment-protein complexes.

A green sea slug, Elysia chlorotica, have been found to use chlorophyll and perform photosynthesis for food for himself. This process is known as kleptoplasty, and no other animals have this ability.

2. Why green and not black?

The other part of the system of green plant photosynthesis is still possible to use the green light spectrum (for example, through the structure of the light-trapping leaves, carotenoids, etc.). Green plants do not use most of the visible spectrum as efficiently as possible. A black plant can absorb more radiation, and this can be very useful, if the additional heat produced is effectively discarded (eg, some plants must close their openings, called stomata, on hot days to avoid losing too much water, that leaves only conduction, convection, and radiation heat-loss as a solution). The question is why a molecule absorbs light is only used to power the green plants and not just black.

Shil DasSarma, microbial geneticist at the University of Maryland, has shown that the archaeal species do use other molecules absorb light, the retina, to extract electricity from the green spectrum. He described the view of some scientists that such a green-light absorbing archae once dominated the Earth's environment. This could leave open a "niche" for green organisms will absorb other wavelengths of sunlight. This is only a possibility, and Berman writes that scientists are still not sure of the explanation one. Astronomer and mathematician Fred Hoyle suspect that the chlorophyll molecule is likely to be between, suggesting similarities in the nature of light absorbing interstellar dust.

Free Articles! Please enter your email.
Print PDF
« Prev Post
Next Post »
Copyright © 2012. My Article - All Rights Reserved | Template Created by Kompi Ajaib | Modified by Ibrahim Lubis