If you're seeing this message, it means we're having trouble loading external resources on our website. Show If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. Most life on Earth depends on photosynthesis.The process is carried out by plants, algae, and some types of bacteria, which capture energy from sunlight to produce oxygen (O2) and chemical energy stored in glucose (a sugar). Herbivores then obtain this energy by eating plants, and carnivores obtain it by eating herbivores. The process During photosynthesis, plants take in carbon dioxide (CO2) and water (H2O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose. The plant then releases the oxygen back into the air, and stores energy within the glucose molecules. Chlorophyll Inside the plant cell are small organelles called chloroplasts, which store the energy of sunlight. Within the thylakoid membranes of the chloroplast is a light-absorbing pigment called chlorophyll, which is responsible for giving the plant its green color. During photosynthesis, chlorophyll absorbs energy from blue- and red-light waves, and reflects green-light waves, making the plant appear green. Light-dependent reactions vs. light-independent reactions While there are many steps behind the process of photosynthesis, it can be broken down into two major stages: light-dependent reactions and light-independent reactions. The light-dependent reaction takes place within the thylakoid membrane and requires a steady stream of sunlight, hence the name light-dependent reaction. The chlorophyll absorbs energy from the light waves, which is converted into chemical energy in the form of the molecules ATP and NADPH. The light-independent stage, also known as the Calvin Cycle, takes place in the stroma, the space between the thylakoid membranes and the chloroplast membranes, and does not require light, hence the name light-independent reaction. During this stage, energy from the ATP and NADPH molecules is used to assemble carbohydrate molecules, like glucose, from carbon dioxide. C3 and C4 photosynthesis Not all forms of photosynthesis are created equal, however. There are different types of photosynthesis, including C3 photosynthesis and C4 photosynthesis. C3 photosynthesis is used by the majority of plants. It involves producing a three-carbon compound called 3-phosphoglyceric acid during the Calvin Cycle, which goes on to become glucose. C4 photosynthesis, on the other hand, produces a four-carbon intermediate compound, which splits into carbon dioxide and a three-carbon compound during the Calvin Cycle. A benefit of C4 photosynthesis is that by producing higher levels of carbon, it allows plants to thrive in environments without much light or water. “Photosynthesis is the process used by green plants and a few organisms that use sunlight, carbon dioxide and water to prepare their food.” The process of photosynthesis is used by plants, algae and certain bacteria that convert light energy into chemical energy. The glucose formed during the process of photosynthesis provides two important resources to organisms: energy and fixed carbon. Read on to explore what is photosynthesis and the processes associated with it. Photosynthesis takes place in special organelles known as chloroplast. This organelle has its own DNA, genes and hence can synthesize its own proteins. Chloroplasts consist of stroma, fluid, and stack of thylakoids known as grana. There are three important pigments present in the chloroplast that absorb light energy, chlorophyll a, chlorophyll b, and carotenoids. Also Read: Photosynthesis Process There are two different types of photosynthesis: Oxygenic photosynthesis is more common in plants, algae and cyanobacteria. During this process, electrons are transferred from water to carbon dioxide by light energy, to produce energy. During this transfer of electrons, carbon dioxide is reduced while water is oxidized, and oxygen is produced along with carbohydrates. During this process, plants take in carbon dioxide and expel oxygen into the atmosphere. This process can be represented by the equation: 6CO2+ 12H2O + LIGHT ENERGY → C6H12O6 + 6O2 + 6H2O Anoxygenic PhotosynthesisThis type of photosynthesis is usually seen in certain bacteria, such as green sulphur bacteria and purple bacteria which dwell in various aquatic habitats. Oxygen is not produced during the process. The anoxygenic photosynthesis can be represented by the equation: CO2 + 2H2A + LIGHT ENERGY → [CH2O] + 2A + H2O Also Read: Difference between Photosynthesis and Respiration Photosynthesis ApparatusThe photosynthesis apparatus includes the following essential components: PigmentsPigments not only provide colour to the photosynthetic organisms, but are also responsible for trapping sunlight. The important pigments associated with photosynthesis include:
PlastidsPlastids are organelles found in the cytoplasm of eukaryotic photosynthetic organisms. They contain pigments and can also store nutrients. Plastids are of three types:
AntennaeAntennae is the collection of 100 to 5000 pigment molecules that capture light energy from the sun in the form of photons. The light energy is transferred to a pigment-protein complex that converts light energy to chemical energy. Reaction CentersThe pigment-protein complex responsible for the conversion of light energy to chemical energy forms the reaction centre. Also Read: Photosynthesis To know more about what is photosynthesis and other topics related to it, keep visiting BYJU’S website or download BYJU’S app for further reference.
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