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Chlorophyll

life science Maturity 7-9 Next article →

Chlorophyll is a group of green pigments found in cyanobacteria, algae, and plants. These molecules are essential for life because they allow organisms to absorb energy from light. This process is known as oxygenic photosynthesis. This is different from the process used by some bacteria, which is called anoxygenic photosynthesis. Chlorophyll molecules are located within the chloroplasts of cells. Specifically, they are arranged in and around structures called photosystems. These photosystems are embedded in the thylakoid membranes of the chloroplasts.

Chlorophyll-a-3D-vdW
Chlorophyll-a-3D-vdW

The mechanism of chlorophyll involves several precise steps to convert light into energy. Most chlorophyll molecules in a photosystem act as antennas. Their primary job is to absorb light energy. Once they absorb this energy, they perform resonance energy transfer. This means they pass the energy to a specific pair of chlorophyll molecules. This pair is located in the reaction center of the photosystem. In green plants, these centers are named P680 and P700. These names refer to the wavelength of light they absorb most strongly.

Chlorophyll ab spectra-en
Chlorophyll ab spectra-en

Once the energy reaches the reaction center, a process called charge separation occurs. The absorbed energy from a photon is transferred to an electron. This process is an oxidation reaction because the chlorophyll donates an electron. The electron then moves through an electron transport chain. This flow of electrons is used to pump H+ ions across the thylakoid membrane. This creates a proton-motive force used to produce ATP, which is stored chemical energy. The process also helps reduce NADP+ to NADPH. NADPH is a universal agent used to turn CO2 into sugars.

Chlorophyll Extraktion
Chlorophyll Extraktion

Chlorophyll is also responsible for producing the oxygen we breathe. In the reaction center, the chlorophyll (P680+) must be reduced back to its ground state. It does this by accepting an electron stripped from water. This reaction breaks water down into O2 gas and H+ ions. This specific biological reaction is the source of practically all the oxygen in Earth's atmosphere. Photosystem I and Photosystem II often work in a series to facilitate this complex electron flow. The identity and function of these pigments are determined by the protein structures surrounding them.

There are several distinct types of chlorophyll identified by scientists. The most common types in green plants are chlorophyll a and chlorophyll b. Chlorophyll a is the most widely distributed form in terrestrial plants. It has a methyl group in its chemical structure. Chlorophyll b has a formyl group instead. This small difference changes how the molecule absorbs light. Other types include chlorophyll c1, c2, d, and f. Chlorophyll f was announced in 2010 as being present in cyanobacteria. It has a molecular formula of C55H70O6N4Mg.

Nonfluorescentchlorophilcatabolites
Nonfluorescentchlorophilcatabolites

The history of chlorophyll research spans over two centuries. Joseph Bienaimé Caventou and Pierre Joseph Pelletier first isolated and named it in 1817. They chose the name from the Greek words for "pale green" and "leaf." In 1906, researchers discovered that magnesium is present in chlorophyll. This was the first time magnesium was detected in living tissue. Between 1905 and 1915, Richard Willstätter performed early work on the molecule. Later, Hans Fischer elucidated the structure of chlorophyll a in 1940. By 1960, Robert Burns Woodward published a total synthesis of the molecule.

Chlorophyll ab spectra-en
Chlorophyll ab spectra-en

Understanding chlorophyll helps us understand the broader energy systems of our planet. The pigments belong to a class of molecules called chlorins. These are related to porphyrins, which are also found in hemoglobin. While hemoglobin uses iron, most chlorophylls bind magnesium at their center. Chlorophyll also works alongside accessory pigments in antenna complexes. These accessory pigments absorb light at wavelengths that chlorophyll cannot reach. This cooperation ensures that the plant captures as much solar energy as possible. This efficient system supports the entire food web on Earth.

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File:Chlorophyll ab spectra-en.svg
Chlorophyll ab spectra-en.svg
File:Chlorophyll-a-3D-vdW.png
Chlorophyll-a-3D-vdW.png
File:Chlorophyll Extraktion.jpg
Chlorophyll Extraktion.jpg
File:Nonfluorescentchlorophilcatabolites.svg
Nonfluorescentchlorophilcatabolites.svg
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