What is the function of chloroplast ?
Chloroplasts in a cell are the sites where photosynthesis takes place. These sites are however not found in all cells of a body but rather only in the photosynthetic cells such as algae and plant cells. Therefore, you cannot find such cells in bacterial or animal cells.
Structuring of the chloroplasts
Those chloroplasts which are featured in higher plants generally are planoconvex or biconvex shaped. Chloroplasts as well can be located in the mesophyll of a cell which is found in the leaves of a plant. For different plants, the shapes of the mitochondria are also different varying from ovoid or discoid to saucer-shaped filamentous shape to spheroid shape. The center of chloroplast is colorless and chloroplasts are vesicular. Some of these sites are structured in such a way that they look like a club whereby the middle zone is thin with ends full of chlorophyll. For algae, the chloroplast is one large site which resembles a stellate plate or rather a spiral band, a network plate. Same cell type has the same number of chloroplast but sizes vary with different plant species.
Function of chloroplast
The chloroplast has various functions and such include:
Chloroplast absorbs light energy then converts that energy to biological form of energy. The chloroplasts are important organelles in plant cells as it that allows for process of photosynthesis to happen. Some protists such as algae also have chloroplasts. Each chloroplast contains chlorophyll, which is a green coloring matter, which converts absorbed light energy from sun to chemical energy which can form sugars such as glucose. This is how food is produced in green plants. Therefore, animal cells do not have chloroplast as they obtain food and nutrients from plants.
The function of chloroplasts which is photosynthesis is divided into two reaction, that is the light and dark reactions. Light reactions occur on thylakoid membranes. These membranes absorb light energy and store it as chemical energy in NADPH form, a form of NADP+ and ATP. This ATP forms that energy used to support dark reactions. That energy is then stored in H+ protons and used later to produce energy in ATP form. Two protein complexes are involved in photosynthesis and they are referred to as photosystems. Therefore, those two photosystems capture light energy and use it to energize those electrons obtained from water and then release energy in those electron transport chain for the mitochondrion.
Hydrogen ions are then pumped by energy of from electrons obtained from water. A concentration gradient would be created, meaning there would be more hydrogen ions inside thylakoid membrane than in stroma. The hydrogen ions would then go back to stroma against cconcentration gradient through ATP synthase which produces ATP. Since that first photosystem reenergizes depleted electrons from photosystem II which photolyzes water to obtain and energize new electrons. This means that photosystem II occurs first followed by photosystem I. ATP which is needed for the dark reactions is hence produced inside the stroma through a process as well referred to as Calvin cycle. This process is a series of reactions which fix carbon dioxide into Glyceraldehyde-3-phosphate molecules. This reaction uses energy and electrons from ATP and NADPH respectively produced in light reactions. Ironically, in most plants, these processes occur daytime despite being called dark reactions.
The first enzyme which is used in Calvin cycle is called RuBisCO and it is used for fixing CO2 into five-carbon Ribulose bisphosphate (RuBP) molecules to form 3-phosphoglyceric acid. 3-phosphoglyceric acid is then converted to glyceraldehyde-3-phosphate using ATP and NADPH. Most of glyceraldehyde-3-phosphate molecules are taken back into RuBP to produce more ATP molecules, but one usually leaves that cycle.
Glyceraldehyde-3-phosphate molecules can combine to form larger sugar molecules called monomers like glucose, galactose, and fructose. These single sugar molecules can also double up to form disaccharides like maltose, sucrose, and lactose. More than two to six monomers combined form oligosaccharides. More than six to a thousand monomers together form polysaccharides such as cellulose and starch. Therefore, this is how food is formed. Carbohydrates are essential for anybody as they are energy-givers, thus it is essential to know how they are formed. Chloroplasts are very vital organelles more so when we are taking about the good health of plants.
