You chloroplasts are the cell organelles in which the reactions of photosynthesis, which use light energy to produce organic molecules. These important structures are found in green algae and plants.
→ What are plastids?
Chloroplasts are organelles that are part of a group known as plastids. These organelles are surrounded by two lipoprotein membranes and have an internal network of complex membranes. Plasmids are usually classified according to the type of pigment they contain. In the case of chloroplasts, the pigment found in greater quantity is the chlorophyll, a green pigment.
→ General characteristics of the chloroplast
Chloroplasts are organelles that contain important pigments such as chlorophyll and carotenoids. Chlorophyll, a green pigment, is present in greater quantity and, therefore, masks the carotenoid, which is a yellow pigment. This green pigment is essential for photosynthesis, and the carotenoid is an important antioxidant. In addition to pigments, it is possible to find starch and oil bodies inside this organelle. Starch is usually stored temporarily and accumulates in the structure when photosynthesis is taking place.
In plants, these important plastids are found in disc shape and usually have between 3 and 10 micrometers in diameter. They are present throughout the plant, but are more differentiated and found in the leaves. Chloroplasts have the ability to reorient themselves in the cell as they need to capture light. However, they usually present with their largest surface positioned parallel to the cell wall.
When analyzing the structure of chloroplasts, we noticed that they have two membranes separated by the intermembrane space and, internally, a differentiated system of membranes. These inner membranes form structures similar to flattened bags, which are called thylakoids and are arranged in an array that is named stroma. The thylakoids are stacked forming the money, structure similar to piles of coins. Each stack is called a granum. Grana thylakoids are interconnected by so-called stromal thylakoids. It is in the thylakoid membrane that pigments are found.
→ Chloroplasts and their similarities to bacteria
Chloroplasts are organelles that are very similar to bacteria, which suggests that the origin of these structures was through a relationship endosymbiotic, as well as mitochondria. As similarities, we can mention:
Similarity between bacterial DNA and chloroplast DNA;
Ribosomes small like those of bacteria and different from the rest of the eukaryotic cell;
Chloroplasts and bacteria reproduce by binary fission.
Curiosity:A leaf mesophyll cell (parenchymal tissue located between the upper and lower epidermis) can have up to 50 chloroplasts.
By Ma. Vanessa dos Santos
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-cloroplasto.htm