What is chloroplast?

It is called chloroplast to an organelle present in the cells of plants, where photosynthesis develops (the process of metabolism that allows certain organisms to synthesize organic substances using sunlight as an energy source).

Delimited by two membranes, chloroplasts present vesicles called thylakoids that harbor molecules capable of transforming the light energy from the sun’s rays into chemical energy. One of these molecules is chlorophyll.chloroplast

The outer membrane of the chloroplast has a good amount of proteins called porins. In the inner membrane, however, the porins are more reduced. Inside the chloroplast, the stroma can be recognized, a cavity where carbon dioxide is fixed. The thylakoids, with chlorophyll, carotenoids and other pigments with photosynthetic capacity, are also found inside.


In the chloroplast, it is also possible to recognize the plastoglóbs, protected by a membrane that is similar to that which covers the thylakoids, from which they detach.

In the plastoglóbulos, they are different organic molecules, between which some lipids are especially common. It should be noted that all the functions of the plastoglobular molecules have not yet been specified.

The chloroplasts are a fundamental part of the cells of the plants since they are the containers of the pigment of the chlorophyll, substance that by the way is essential at the time of the conformation accomplishment of the photosynthesis.


Chlorophyll is the basic and most important element of plants and algae, it is characterized by its green color, being specially composed of carbon and hydrogen and we find it as we already pointed out in chloroplasts.

Photosynthesis is an essential metabolic process that takes place in plants since it is through this that their cells are able to transform inorganic matter into organic, while the sun’s energy is essential in combination with chlorophyll so that the process is generated successfully.

Without photosynthesis, life on planet earth would be impossible because it is precisely this procedure that is responsible for correctly fixing carbon dioxide in the atmosphere and for the necessary oxygen to be released. And also it is to guarantee the balance between for example the plants and the human beings. People are one of the main beneficiaries of this release of oxygen that is generated in photosynthesis.

So, how are chloroplasts that precisely facilitate this natural process not going to be very important?

Photosynthesis is carried out in two phases, each one developed in different sectors of the chloroplast.

The so-called light phase is produced in the membrane that surrounds the thylakoids, where the elements that convert light energy into chemical energy are found. The dark phase, on the other hand, is generated in the stroma. There an enzyme is responsible for fixing carbon dioxide.


The content of the cell is divided into several compartments and this phenomenon represents a challenge at the organizational level due to the concept is known as protein trafficking, which, in a eukaryotic cell, regulates:

* the classification signals, a reduced number of amino acids that form a compound known by the name of a peptide, which in this case points out with lysosomal enzymes of the mannose-phosphate group the proteins that are secreted.

* the receptors that notice these signals and move the proteins in which they are contained to the relevant compartments.

The import of proteins by means of one or more external membranes that act as limits occurs in four cellular organelles: the chloroplast, the nucleus, the peroxisomes and the mitochondria.

An example can be seen in the proteins that import these organelles in the rough endoplasmic reticulum, which have amino acid sequences that act as “domicile” for the receptors located in the outer membrane to recognize them.


While in the rough endoplasmic reticulum the importation of the proteins is carried out almost contemporary to the translation, in the other organelles it occurs after the synthesis in the free ribosomes of the cytoplasmic matrix (the so-called cytosol) is completed.

In the specific case of chloroplasts, proteins can reach a well-defined series of subcompartments: internal and external envelope membranes; intermembranous space; stroma; thylakoid membrane; thylakoid light.

The mechanisms used by the chloroplast to import proteins are very similar to those of the mitochondria, although the evolution of their translocations has been different.

It is important to mention that chloroplasts are present, beyond plants, in certain animals that acquire them through different processes, such as kleptoplasty, an endosymbiosis that consists of the plastids being assimilated by organisms that do not have them.

The kleptoplasty has the objective that the organisms that acquire plastos can make use of their autotrophic capacity. This behavior has been observed in almost all sacoglossus molluscs and in certain dinoflagellates.

These organelles can be seen surrounded by membranes and in addition to their ovoid physical form have vesicles in which the pigments of chlorophyll and other molecules are contained.


In the specific case of plants, chloroplasts are plausible to develop in accordance with instances of light and thanks to other smaller organelles that are known as proplasts.

When the cells of the plants are divided into the different zones of the same one and along with the growth of the plant, these proplasts are also divided by the fission reaction.

Thanks to this situation are that the cells considered as daughters are able to generate per se chloroplasts.

Meanwhile, as far as algae are concerned, there is a differentiation in the process just described, since chloroplasts can be divided without the need for proplasts to mediate.

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