What is the difference between plant cells and animal cells? The answer lies in the color of plants: their color depends on the content of pigment in the cells. These pigments are stored in special organelles called plastids.
What are plastids in biology?
The difference between plant cells and 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 the plastids of plants that is responsible for their color.
In the cell of any eukaryotic organism, non-membrane, single-membrane and double-membrane organelles are isolated. Plastids and mitochondria belong to the last type of cellular structures, since they are surrounded by two layers of CPM.
What are cell plastids? Types of plastids
- 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 to increase the active surface of the organelle. What are green plastids? These are chloroplasts that contain pigments.green - chlorophylls. There are several groups of these molecules, each of which is responsible for its specific functions. In higher plants, chlorophyll a is the most common, which is the main acceptor of solar energy during photosynthesis.
- Leucoplasts. Colorless plastids that perform a storage function in plant cells. They can have an irregular shape, ranging from spherical to fusiform. Leucoplasts often accumulate around the cell nucleus, and they can be detected under a microscope only in the case of a large number of granules. Depending on the nature of the stored substance, three types of leukoplasts are distinguished. Amyloplasts serve as a container for carbohydrates, which the plant wants to keep up to a certain point. Proteoplasts store various proteins. Oleoplasts accumulate oils and fats, which are the source of lipids. This is what a plastid is, which performs the function of storage.
- Chromoplasts. The last type of plastid, which has a characteristic yellow, orange or even red color. Chromoplasts are the final stage in the development of chloroplasts, when chlorophyll is destroyed, and only fat-soluble carotenoids remain in plastids. Chromoplasts are found in flower petals, mature fruits, and even in plant stems. The exact meaning of these organelles is not exactly known, but it is assumed that they are a receptacle for carotenoids, and also give plants a specific color. This coloration attracts pollinating insects, which encourages plant reproduction.
Leucoplasts and chromoplasts are not capable of photosynthesis. Chlorophyll in these organelles was reduced or disappeared, so their function changed cardinally.
The role of chloroplasts in the transfer of genetic information
What is a plastid? This is not only the energy station of the cell, but also the repository of a part of the cell's hereditary information. It is presented in the form of a circular DNA molecule, which resembles the structure of the prokaryotic nucleoid. This circumstance makes it possible to assume a symbiotic origin of plastids, when bacterial cells are absorbed by plant cells, losing their autonomy, but leaving some genes.
Chloroplast DNA refers to the cytoplasmic inheritance of the cell. It is transmitted only with the help of germ cells that determine the female sex. Sperm cannot transfer male plastid DNA.
Because chloroplasts are semi-autonomous organelles, many proteins are synthesized in them. Also, when dividing, these plastids replicate on their own. However, most chloroplast proteins are synthesized using information from nuclear DNA. This is what a plastid is in terms of genetics and molecular biology.
Chloroplast is the energy station of the cell
In the process of photosynthesis, many biochemical reactions take place on the thylakoids of chloroplasts. Their main task is the synthesis of glucose, as well as ATP molecules. The latter carry in their chemical bonds a large amount of energy, which is vitalcage.
What is a 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 are attached to ADP molecules, and at the output the cell receives ATP.
