Chloroplast is one of the cell’s permanent organelles. It implements the most important process of planetary significance - photosynthesis.
General plan for the construction of two-membrane organelles
Each organelle consists of a surface apparatus and internal contents. Chloroplasts and mitochondria are structures of prokaryotic cells - organisms with a nucleus. The surface apparatus of these organelles consists of two membranes, between which there is 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 species of fungi, plants and animals. They serve for the synthesis of ATP - a substance that is a kind of supply of energy cells. Chloroplast is also a two-membrane organelle, which belongs to the group of plastids.
Variety of plastids
In the cells of living organisms, there are three types of plastids. These are chloroplasts, chromoplasts and leukoplasts. They differ in color, structural features and functions. Chloroplast is a green plastid that contains the chlorophyll pigment. Although often, due to the presence of other dyes, they can be brown and red. For example, in the cells of various algae. At the same time, chromoplasts are always colorless. Their main function is the storage of nutrients. So, potato tubers contain starch. Chromoplasts are plastids that have carotenoid pigments. They give color to various parts of plants. Brightly colored root vegetables of carrots and beets, flower petals are a vivid example of this.
Plastids can transform. Initially, they arise from the cells of the educational tissue, which are small bubbles surrounded by two membranes. In the presence of solar energy, they are converted to chloroplasts. With the aging of leaves and stems, chlorophyll begins to break down. As a result, green plastids turn into chromoplasts.
Here are a few more examples. Everyone saw that in the fall leaves change 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 in the development of plastids is 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 a plant. Chlorophylls are 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 creatures. In particular, in all plants, certain 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 forms outgrowths. They are directed inside the content of chloroplasts, 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 located singly or collected in piles of 5-20 pieces. They are called grains. Pigments are located on the structures of thylakoids. The main ones are chlorophylls, and carotenoids play an auxiliary role. They are necessary for the implementation of 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 polysaccharide glucose and oxygen. Without this gas, breathing of all creatures 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 is the accumulation and storage of a certain amount of energy. This occurs during the onset of favorable environmental conditions: the availability of sufficient water, solar energy, food. During the course of vital processes, ATP breaks down with the release of a certain amount of energy. It is spent during the implementation of growth, development, movement, reproduction and other processes of life. The functions of chloroplasts also consist in the fact that some lipids, membrane proteins, and enzymes involved in photosynthesis are synthesized in these plastids.
The importance of photosynthesis
Chloroplast is the link between the plant and the environment. As a result of photosynthesis, not only oxygen formation occurs, but also a cycle in the nature of carbon and hydrogen, maintaining a constant atmosphere composition. This process limits the carbon dioxide content, which prevents the greenhouse effect, overheating of the earth's surface and the death of many living creatures on the planet. Plastids, chloroplasts, which are organelles of cells, carry out the most important functions, causing the existence of life on Earth.