Chloroplast Function

Chloroplasts are those subunit in a plant cell, which produce food for a plant through the process of photosynthesis. Chloroplasts are somewhat similar to mitochondria found in animal cells which can produce energy. Chloroplasts reproduce by the process of division of cells and have their own genetic systems. It's the chloroplasts which convert carbon dioxide into carbohydrates, which are consumed by plants. Moreover amino acids, lipid components and fatty acids of the cell membranes are synthesized by chloroplasts. In addition to that, chloroplasts reduce nitrogen into ammonia and other organic compounds. Once you have got a basic idea of chloroplast function, let's take a look at how they function in a plant cell.

Chloroplast Function in a Plant Cell

Chloroplast contain an important component called chlorophyll, which is responsible for production of food. It's the chlorophyll which gives the chloroplast and in turn, leaves its characteristic green color. Chlorophyll contained in the chloroplasts is responsible for absorbing sunlight. It's through the process of photosynthesis that a plant makes food for itself. The process includes absorbing the energy from the sun so as to create sugar. When sunlight hits a chloroplast, the chlorophyll in it uses the energy and in combination with carbon dioxide and water forms sugar and oxygen. Plants use these sugars for survival and the oxygen released is used by animals to breathe.

Chloroplast Function and Structure

The chloroplasts are usually 5-10 micrometer long and consist of circular DNA molecules. They are bound by a two-layered membrane which is known as the chloroplast envelope. Besides these membranes, they have another membrane which is known as the thylakoid membrane. This membrane has numerous flat disc like structures, called the thylakoids and they are arranged in piles called the grana. The internal composition of the chloroplast is highly complex due its membrane structure. The chloroplast is divided into three compartments - the thylakoid lumen, which is the outer-most membrane, the stroma the middle membrane and the intermembrane space, the space between a chloroplasts' two membranes.

Even though the structure is highly complex, the functions of each of these membranes are not that complex. The outermost membrane of the chloroplast envelope contains porins which absorb sunlight. They also contain small molecules which can easily penetrate the membranes and transport sun's energy. On the other hand, the inner membrane or the stroma is not permeable to metabolites and ions, thereby trapping sun's energy in them. The stroma contains a number of metabolic enzymes, which are responsible for converting carbon dioxide to carbohydrates during the process of photosynthesis.

If seen under an electronic microscope, the thylakoid membranes look like alternate light-and-dark bands and each of them are 0.01 micrometer thick. These membranes consist of some antenna complexes and it's these which contain carotenoids, chlorophyll besides protein, which holds these pigments together. The antenna complexes increase the area of the chloroplasts, thereby allowing them to capture more light, i.e. photons with higher wavelengths. Energy absorbed is then captured and transferred to the center of the chloroplast. The chlorophyll molecules gets ionized, thereby producing excited electrons, which in turn passes light energy to the stroma, so as to produce food. A chloroplast can connect with its neighbors by extending its external membranes to form stromules (tubular structures). This facilitates the transfer of proteins within the network of chloroplasts.

Chloroplast functions are quite complex, and to know the complete range of functions of chloroplasts, you would need to understand the complete leaf structure besides the other chemical reactions in leaves. We have tried to give a brief and a basic idea of the functions of chloroplast and its structure. Hope, this helps you in understanding the chloroplast function at its basic.