TILACOIDS: What are, function and structure

Tilacoids are Membranous structuresalso known as flattened sacks or vesicles, interconnected to each other, forming a Continuous and closed system. They are involved in photosynthesis, and we can find them in cyanobacteria and chloroplasts. It is believed that they have their origin in photosynthetic bacteria and are closely related to the development of photosystem II, which allows oxygenic photosynthesis. In the upper plants, chloroplasts emerge from undifferentiated proplastications that initially have few internal membranes. As chloroplasts differ, a tilacoidal membrane system is formed that requires continuous synthesis for maintenance during cell division.

The tilacoids They constitute the main structure within mature chloroplasts. Its composition and architecture are intimately linked to the evolution of chloroplasts from simple proplasticas. These membranes are lipid bicapas with a specific composition of glycerolipids, standing out for a high content of galactolipids, such as diglycerid galactosyl, which are almost exclusive to plastidic membranes. Galactolipids have two chains of unsaturated fatty acids, unlike other lipids that commonly contain one.

Tilacoid formation is a complex process, which may include the invagination of internal envelope in young plastids. In fully developed chloroplasts, the tilacoid membrane demonstrates to be a dynamic system that adapts to light variations through protein displacement.

• They catch the energy of the light and transforms it into forms of chemical energy, ATP and Nadph. During this process, water is oxidized and oxygen is released. These functions are performed by five great protein complexes: photosystem I with united antennas, photosystem II with united antennas, the light collection complex II, cytochrome b 6 fy the ATP synthase.
• Absorb the photons of sunlightthus initiating the photochemical phase of photosynthesis.
• The chemical energy that occurs during photosynthesis will be used later in cellular respiration.
• Contain Chlorophyll, xantophils and carotenoidswhich serves to capture light and the photosynthetic process.
• It has enzymes, lipids and proteins necessary to carry out the photosynthetic reactions.
• Are Responsible for ATP production (adenosine triffosphate) and facilitate electron transport chain.
• The energy that occurs in plant cells is necessary to survive.
• The grana -shaped structure of the tilacoid provides a wide surface to maximize light collectionwhich improves the efficiency of the photosynthetic process.

The tilacoids are surrounded by a tilacoidal membranewhich houses the essential multiprotean complexes for the luminous reactions of photosynthesis. It is mainly composed of photosystems I and II, together with its associated light collection complexes, cytochrome b6 fy the ATP synthase. These complexes are formed by numerous peripheral and integral proteins, as well as a variety of pigments and cofactors. The distribution of the components in the Tilacoidal membrane is not homogeneous. He Photosystem i It is predominantly in the stroma sheets unantilated, while the Photosystem II It is the main component in grana batteries.

On the other hand, protein components in tilacoid membranes are specificly distributed; For example, photosystem II is predominantly located in stacked regions, while photosystem I and ATP synthase are found in stroma tilacoids and in unantilated areas. This asymmetric disposition It is crucial to maximize the efficiency of photosynthetic reactions.

The tilacoidal membrane is rich in glycolipids, especially galactolipids, which represent about 70% of the lipid fraction. These lipids, together with plastoquinone and other components, maintain the fluidity of the membrane, despite a high protein/lipid ratio. In addition, the tilacoidal system allows the translocation of protons to the lumen, which is essential for the generation of ATP through the ATP synthase.

Now that you know what tilacoids are, you may also be interested in this article about the prokaryotic cell: characteristics, parts and functions.

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