Chloroplast is one of the permanent organelles of the cell. It carries out the most important process of planetary significance - photosynthesis.
General plan of the structure of two-membrane organelles
Each organelle consists of a surface apparatus and internal contents. Chloroplasts and mitochondria are the structures of prokaryotic cells - organisms that have a nucleus. The surface apparatus of these organelles consists of two membranes, between which there is a free space. Spatially and anatomically, they are not connected with other structural parts of the cell and take part in energy metabolism. Mitochondria are the organelles of most fungi, plants, and animals. They serve for the synthesis of ATP - a substance that is a kind of energy reserve of cells. The chloroplast is also a double-membrane organelle that belongs to the plastid group.
Plastid diversity
There are three types of plastids in the cells of living organisms. These are chloroplasts, chromoplasts and leukoplasts. They differ in color, structural features and functions. Chloroplast is a green plastid containing the pigment chlorophyll. Although often, due to the presence of other coloring substances, they can be both brown and red. For example, incells of various algae. At the same time, chromoplasts are always colorless. Their main function is to store nutrients. So, potato tubers contain starch. Chromoplasts are plastids that have carotenoid pigments. They give color to various parts of plants. The brightly colored carrot and beet roots and flower petals are a prime example of this.
Plastids can transform. Initially, they arise from the cells of the educational tissue, which are small vesicles surrounded by two membranes. In the presence of solar energy, they are converted into chloroplasts. As leaves and stems age, chlorophyll begins to break down. As a result, green plastids turn into chromoplasts.
Let's give some more examples. Everyone saw that in autumn the leaves change their color. This is due to the fact that chloroplasts turn into red, yellow, burgundy plastids. The same transformation occurs when the fruit ripens. In the light, potato tubers turn green: chlorophyll begins to form in leukoplasts. The final stage of plastid development are chromoplasts, since they do not form other types of similar structures.
What are pigments?
The color, functions and structure of the chloroplast are due to the presence of certain substances - pigments. By nature, they are organic compounds that color different parts of the plant. Chlorophyll is the most common of them. They are found in the cells of algae and higher plants. Carotenoids are also often found in nature. They are found in most known living beings. In particular, in all plants, some types of microorganisms, insects, fish and birds. In addition to giving color to various organs, carotenoids are the main visual pigments, providing visual and color perception.
Membrane structure
Plant chloroplasts have a double membrane. And the outside is smooth. And the inner one forms outgrowths. They are directed inside the contents of the chloroplast, which is called the stroma. Special structures, thylakoids, are also associated with the inner membrane. Visually, they are flat single-membrane tanks. They can be placed singly or assembled in stacks of 5-20 pieces. They are called grains. Pigments are located on the structures of the thylakoids. The main ones are chlorophylls, and carotenoids play an auxiliary role. They are essential for photosynthesis. The stroma also contains DNA and RNA molecules, starch grains and ribosomes.
Chloroplast functions
The main function of green plastids is the synthesis of organic substances from inorganic ones due to the energy of light. Its products are the polysaccharide glucose and oxygen. Without this gas, the breathing of all beings on Earth will be impossible. This means that photosynthesis is a vital process of planetary significance.
The structure of the chloroplast determines its other functions. ATP synthesis occurs on the membrane of these plastids. The significance of this process lies inaccumulation and storage of a certain amount of energy. This happens during the onset of favorable environmental conditions: the presence of a sufficient amount of water, solar energy, food. During the course of life processes, ATP is split with the release of a certain amount of energy. It is spent during the implementation of growth, development, movement, reproduction and other life processes. The functions of chloroplasts also lie in the fact that some lipids, membrane proteins and enzymes involved in the process of photosynthesis are synthesized in these plastids.
Importance of the process of photosynthesis
Chloroplast is the link between the plant and the environment. As a result of photosynthesis, not only the formation of oxygen occurs, but also the circulation of carbon and hydrogen in nature, maintaining a constant composition of the atmosphere. This process limits the content of carbon dioxide, which prevents the occurrence of the greenhouse effect, overheating of the earth's surface and the death of many living creatures on the planet. Plastids chloroplasts, which are cell organelles, perform the most important functions, causing the existence of life on Earth.
