What is plastid in biology?

What is the difference between plant cells and animals? The answer lies in the color of plants: their coloring depends on the pigment content in the cells. These pigments accumulate in special organelles, which are called plastids.

What is plastids in biology?

The difference of plant cells from animals is the presence of chloroplasts, leukoplasts and chromoplasts. These organelles are responsible for a number of functions, among which the process of photosynthesis clearly dominates. It is the pigment contained in plant plastids that is responsible for their color.

In the cell of any eukaryotic organism, non-membrane, single-membrane and two-membrane organelles are isolated. Plastids and mitochondria belong to the latter type of cellular structures, since they are surrounded by two layers of MTC.

What are cell plastids? Types of plastids

1. Chloroplasts. The main two-membrane organelles of plant cells responsible for the processes of photosynthesis. They consist of thylakoids on which photosynthetic complexes are located. The function of thylakoids is an increase in the active surface of the organelle. What is green plastids? These are chloroplasts, which contain green pigments - chlorophyll. There are several groups of these molecules, each of which is responsible for its specific functions. In higher plants the most common chlorophyll a , which is the main acceptor of solar energy in photosynthesis.
2. Leukoplast. Colorless plastids that perform a storage function in plant cells. They can have an irregular shape, ranging from spherical to spindle-shaped. Leukoplasts often accumulate around the nucleus of the cell, and in a microscope they can be found only in the case of a large number of granules. Depending on the nature of the stored material, there are three types of leukoplasts. Amyloplasty serves as a receptacle for carbohydrates, which the plant wants to retain until a certain point. Proteoplasty stores various proteins. Oleoplasts accumulate oils and fats, which are a source of lipids. That's what plastid, which performs the function of storage.
3. Chromoplast. The last type of plastids, which has a characteristic yellow, orange or even red color. Chromoplasts are the final stage of the development of chloroplasts, when chlorophyll is destroyed, and only fat-soluble carotenoids remain in the plastids. Chromoplasts are found in flower petals, mature fruits and even in plant trunks. The exact meaning of these organelles is not known exactly, but they assume that they are a container for carotenoids, and also give plants a specific color. This color attracts insect pollinators, which promotes the multiplication of plants.

Leukoplasts and chromoplasts are not capable of photosynthesis. Chlorophyll in these organelles was reduced or disappeared, so their function changed in a coordinated way.

The role of chloroplasts in the transfer of genetic information

What is plastid? This is not only the power station of the cell, but also the storehouse of some of the hereditary information of the cell. It is represented as a circular molecule of DNA, which resembles the structure of the prokaryotic nucleoid. This circumstance makes it possible to assume the symbiotic origin of plastids, when bacterial cells are absorbed by plant cells, losing their autonomy, but leaving some genes.

The DNA of chloroplasts refers to the cytoplasmic heredity of the cell. It is transmitted only with the help of sex cells that determine the female sex. Spermia can not transmit male plastid DNA.

That's how chloroplasts are semi-autonomous organelles, many proteins are synthesized precisely in them. Also in the division, these plastids are self-replicating. However, most of the chloroplast proteins are synthesized using information from the DNA of the nucleus. That's what plastids are from the point of view of genetics and molecular biology.

Chloroplast is a cell power station

In the process of photosynthesis on the thylakoids of chloroplasts, many biochemical reactions take place. Their main task is the synthesis of glucose, as well as the molecules of ATP. The latter carry in their chemical bonds a large amount of energy that is vital to the cell.

What is plastid? It is a source of energy along with mitochondria. The process of photosynthesis is divided into light and dark stages. During the light stage of photosynthesis, phosphorus residues attach to ADP molecules, and at the output, the cell receives ATP.