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Photosynthesis and Transpiration
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The importance of photosynthesis and how it helps organisms to survive through food production in plants.

Sudipt kumar
I am Sudipt. Written 3 Civil service mains. Other exams cleared - SSC CGL, GATE, CAT, FTII, IISc, TISS. I love playing table tennis. I have

Unacademy user
sir it is very useful for our preparation
  1. Photosynthesis What is Photosynthesis? All organisms require energy for their chemical reactions. These reactions may be involved with reproduction, growth, or other activities. Photosynthetic organisms such as plants use light energy to produce carbohydrate (glucose). Glucose can be used at a later time to supply the energy needs of the cell. Photosynthesis is therefore a process in which the energy in sunlight is stored in the bonds of glucose for later use. The equation for photosynthesis shows that these compounds are used to produce glucose 6CO2 6H20EnergyC6H1206+ 602 Light Electromagnetic Spectrum Sousce NCERT Bial Light behaves as if it were composed of "units" or "packets" of energy that travel in waves. These packets are photons. The wavelength of light determines its color. For example, The wavelength of red is about 700 nm and the wavelength of blue light is about 470 nm. Scanned by CamScanner


  2. Photosynthetic Pigments (Source-NCERT Biolo Pigments are molecules that absorb light. When a photon an electron in an atom contained within the molecule becomes excited. further from the nucleus of the atom of light strikes a photosynthetic pigment, Energized electrons move The excited (energized) molecule can pass the energy to another molecule or release it in the form of light or heat. Chlorophyll A is the main photosynthetic pigmeorganisms except bacteria. Other pigments called accessory pigments absorb slightly different wavelengths of light. The combination of all of the pigments increases the range of colors that plants can use in photosynthesis. Accessory pigments include chlorophyll b and a group of pigments called carotenoids. They do not participate directly in photosynthetic reactions but are able to pass their energy to chlorophyll a. Scanned by CamScanner


  3. 2 Sets of Reactions Light-Dependent Reactions The light-dependent reactions require light These reactions occur in the thylakoid membrane Scanned by CamScanner


  4. Light-Independent Reactions Light-independent reactions occur in stroma of the chloroplast in light or dark conditions. They function to reduce Co2 to glucose.u Calvin Cycle (Light-independent Reactions) The products of the light reactions (ATP and NADPH) are used to reduce CO2 to carbohydrate in th Calvin cycle. The Calvin cycle produces a 3-carbon sugar called glyceraldehyde 3-phosphate (G3P),. G3P is be us to synthesiz glucose and other organic compounds needed by the cel. The words "CO2 fixation" refer to the attachment of CO2 to an organic compound: each CO2 bi to a 5-carbon ribulos bisphosphate (RuBP) molecule. Carbon dioxide fixation is catalvzed b' RuBp carboxylase (rubisco) Scanned by CamScanner


  5. Photorespiration Source - NCERTBe When the concentration of CO2 is low, oxygen will bind to the active site of rubisco. The resulting reactions do not produce sugar and they consume ATP. In addition, organic compounds that are involved in photosynthesis are broken down. The Calvin Cycle in C4 Leaves C4 plants have a pathway that allows them to fix Co2 at lower concentration than C3 plants. This gives them an advantage during hot, dry conditions because they can keep the stomata closed for longer periods of time to prevent dehydration before photorespiration occurs. In CA plants, cO2 is fixed in the mesophyll cells by PEP carboxylase, an enzyme that is more efficient CO2 is than rubisco. The resulting organic compound is transported to the mesophyll cells where the released for the Calvin Cycle. The movement of CO2 into the bundle sheath cells maintains a higher concentration than would otherwise be possible. Scanned by CamScanner


  6. CAM (crassulacean-acid metabolism) photosynthesis is found in most desert plants, particularly the succulents (plants that store water in thick, fleshy leaves). CAM plants keep their stomata closed during the day to conserve water. At night, the stomata open to allow co2 to enter. CO2 is incorporated into organic acids which are then stored within the mesophyll cells. During the day, CO2 is released from the organic acids to supply the Calvin Cycle. CAM plants are 5 to 7 times more efficient than C4 plants. Scanned by CamScanner