Chlorophyll

The word chlorophyll comes from the Greek Chloros which means green and Phyllos means leaf. This term was introduced in 1818, where the pigment was extracted from plants using organic solvents. Chlorophyll is a green pigment in plants, algae and photosynthetic bacteria. This compound plays a role in the process of photosynthesis of plants by absorbing and converting the energy of sunlight into chemical energy.

In the process of photosynthesis, there are 3 main functions of chlorophyll namely the first utilizing solar energy, the second can trigger the fixation of CO2 into carbohydrates and third provide an energetic basis for the ecosystem as a whole. Carbohydrates produced from photosynthesis through the process of anabolism are converted into proteins, fats, nucleic acids, and other organic molecules.

In photosynthetic cells in plants, chlorophyll is in small, round-shaped chloroplasts, solid protoplasmic bodies containing grana, or disks, where chlorophyll molecules are located. Most chlorophyll absorbs light in the red and blue-violet parts of the light spectrum. Whereas the green part is not absorbed and reflected, then gives a distinctive color chlorophyll.

Chlorophyll Function

The function of chlorophyll in plants is to absorb light and transfer it through plants during photosynthesis. Chlorophyll in plants is found in thylakoids, chloroplasts. Chlorophyll uses sunlight to make sugar which is a key substance in chloroplasts, which are central to food production from plant cells.

Sunlight illuminates chloroplasts in plants and is then absorbed by chlorophyll and then combined with carbon dioxide and water to make glucose, or sugar. This process will also create oxygen, which animals will later use in their own respiration.

Mitochondria then use the sugar produced by chlorophyll to be converted into energy that can be used by plants. Stroma manages carbon dioxide intake from plants, which plays an important role for the whole process. Chlorophyll is not the only structure that uses light. For example, algae have phycoerythrin, while brown algae use fucoxanthin.

Chlorophyll absorbs all colors of sunlight besides green, which is why leaves can appear green to the human eye. But in the fall, leaves slowly lose their chlorophyll because the tree closes the photosynthesis process. This is because there is not enough sunlight to complete the photosynthesis process. When the green from the chlorophyll fades, the yellow or orange part that runs along the leaf is then visible because of food stored in the leaf.

In the process of photosynthesis can occur in two steps, namely the light reaction and dark reaction. Bright reactions require light which then photon energy in the sun is used for photolysis or the breakdown of H2O, subsequently producing the production of ATP and NADPH2, reducing power.

Whereas the dark reaction does not require light and only involves the reduction of CO2 to glucose (C6H12O6) which occurs in a series of steps that are controlled by several enzymes. Dark reactions cannot occur without light because of the final product of the light reaction, namely ATP and NADPH2, although it does not require direct light.

The Role of Chlorophyll in Photosynthesis

Photosynthesis is a metabolic process in plants to form carbohydrates that use CO2 from free air and water from the soil with the help of sunlight and chlorophyll. Photosynthesis is a process of preparing chemical compounds using light energy. The process of photosynthesis will occur if there is light and an intermediate pigment, chlorophyll.

Chlorophyll acts to attract electrons from sunlight to cause photosynthesis. Its chemical structure is the same as heme, a ring compound in haemaglobin, where the Fe axis in heme is replaced by Mg. Chlorophyll acts as an absorber of energy from sunlight so that it turns into a high-energy molecule, which can release electrons from water molecules and protons from oxygen. The chemical reaction of photosynthesis is as follows.

There are 2 photosystems; chlorophyll 1 photosystem and chlorophyll 2 photosystem. Chlorophyll 1 photosystem absorbs long wave (red) light, chlorophyll 2 photosystem absorbs shortwave light which belongs to chlorophyll 1 photosystem is chlorophyll a, whereas chlorophyll 2 photosystem is chlorophyll 2 and b, in other words chlorophyll a absorbs long and slightly short waves. Chlorophyll b only absorbs shortwave light (Yatim in Arrohmah, 2007).

Photosynthesis begins when light ionizes the chlorophyll molecule in photosystem II so that the electrons are released and the electrons are transferred along the electron transport chain. Energy from these electrons is used for photophosphorylation which produces ATP. This reaction causes photosystem II to experience a lack of electrons which can be met by electrons from the ionisation of water that occurs simultaneously with chlorophyll ionization. The results of this water ionisis are electrons and oxygen.

At the same time as photosystem II ionization, light also ionizes photosystem I, releasing electrons transferred along the electron transport chain which ultimately reduces NADP to NADPH. ATP and NADPH produced in photosynthesis trigger various biochemical processes. In plants the biochemical process that is triggered is the calvin cycle where carbon dioxide is converted to ribulose (then becoming a sugar like glucose). This reaction is called the dark reaction because it does not depend on the presence or absence of light.

When light hits matter, it can be reflected, transmitted or absorbed. Certain pigments will absorb light with a certain wavelength and absorbed light will disappear by releasing heat. If a pigment is exposed to white light, the color shown is the color reflected or passed on by the pigment in question. Chlorophyll pigments absorb more visible light in blue (400-450 nm) and red (650-700 nm) than green (500-600 nm).

Plants can get all their energy requirements from the red and blue spectrum in the visible light spectrum region and in the region between 500-600 nm very little light is absorbed. So the green color of the leaves is caused by chlorophyll absorbing red and blue light and continuing and reflecting green light.

 

Chlorophyll in Oxygen Production

The byproduct of the photosynthesis process is oxygen. Plants can use oxygen in cellular respiration, but they also release excess oxygen into the air. Therefore, the oxygen produced by these plants has many benefits to support life on Earth.

Oxygen is produced by plants in the first part of the photosynthetic light cycle. Plants divide water molecules to produce electrons, hydrogen ions, and diatomic oxygen (O2). The electron then supplies the electron transport chain which drives the production of ATP. Finally, oxygen is released into the air so this is the oxygen we breathe.

Factors That Influence Chlorophyll Formation

The formation of chlorophyll is influenced by several factors as follows:

      • Carrier factor, if there is no chlorophyll then the plant will look white (albino), for example like a corn plant.
      • Sunlight, where chlorophyll can be formed due to direct sunlight on plants.
      • Oxygen, if there is no oxygen, it cannot form chlorophyll even if given sunlight.
      • Carbohydrates can help the formation of chlorophyll to experience growth. Without carbohydrates, the leaves are unable to produce chlorophyll.
      • Nitrogen, Magnesium, and Iron. If lacking one of these substances will lead to chlorosis in plants.
      • The elements Mn, Cu, and Zn. If there are no such elements, the plant will experience chlorosis as well.
      • Water, lack of water in plants results in the disintegration of chlorophyll as occurs in grass and trees in the dry season.
      • Temperature 30-400C is a good condition for the formation of chlorophyll in most plants, but the best is at temperatures between 26-300C (Dwidjoseputro, 1981

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