The idea of Van Neil was supported by R. Hill. The carbon dioxide fixation takes place in the stroma of chloroplasts because it has enzymes essential for fixation of CO2 and synthesis of sugar. It synthesizes organic food from inorganic raw materials. We know that the enzyme RUBISCO (Ribulose biphosphate carboxylase oxygenase) catalyzes the carboxylation reaction, where CO2 combines with RuBP for calvin cycle (dark reaction of photosynthesis) to initiate. Thus, initially light intensity was limiting the rate of photosynthesis. Photosynthetic pigments absorb visible part of the radiation i.e., 380 mμ, to 760 mμ. Fixation of CO2 occurs via different pathways in different organisms. While the former is a normal process in some green plants, the latter is an abnormal and injurious process occurring in extremely intense light resulting in destruction of cellular components, cells and tissues. Share Your Word File But this enzyme RUBISCO, under intense light conditions, has the ability to catalyse the combination of O2 with RuPB, a process called oxygenation. Photosynthesis decreases the concentration of carbon dioxide which is being added to the atmosphere by the respiration of organisms and burning of organic fuels. If these assimilatory powers are given to stroma fraction in the presence of carbon dioxide and absence of light then carbohydrate is synthesized. Photosynthesis is an oxidation reduction process in which water is oxidized and carbon dioxide is reduced to carbohydrate. Photosynthesis is the most important natural process which sustains life on earth. This process does not directly depend on the presence of light but is dependent on the products of the light reaction, i.e., ATP and NADPH, besides CO2 and H2O. Carbon dioxide from atmosphere is accepted by Phosphoenol pyruvic acid (PEPA) present in stroma of mesophyll cell chloroplast and it converts to oxaloacetic acid (OAA) in the presence of enzyme PEPCO (Phosphoenolpyruvate carboxylase). They can very well grow in saline soils because of presence of C4 organic acid. It occurs under conditions of low light intensity, wavelength longer than 680 nm and when CO2 fixation is inhibited. 9. Chlorophyll is an essential internal factor for photosynthesis. It is usually constant for a plant species but rarely it varies. Our mission is to provide an online platform to help students to share notes in Biology. It is of two types: The normal state of the molecule is called as ground state or singlet state. This 4-C acid (OAA) enters into the chloroplast of bundle sheath cell and there it undergoes oxidative decarboxylation yielding pyruvic acid (3C) and CO2. Energy is used to pump protons across a membrane, to create a gradient or a high concentration of protons within the thylakoid lumen. The pathway by which all photosynthetic eukaryotic organisms ultimately incorporate CO2 into carbohydrate is known as carbon fixation or photosynthetic carbon reduction (PCR.) Emerson and his co-workers (1957) found that the inefficient far red light in Chlorella beyond 680nm could be made fully efficient if supplemented with light of short wave length. Photosynthesis occurs when plants use light energy to convert carbon dioxide and water into glucose and oxygen. 15. If photosynthesis is allowed to proceed in presence of CO218 and normal water then heavy oxygen is not evolved. 1. C4 plants are better adapted to environmental stress than C3 plants. The carbon dioxide released in bundle sheath cell reacts with RuBP (Ribulose 1, 5 bisphosphate) in presence of RUBISCO and carry out Calvin cycle to synthesize glucose. 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