(4) uses of energy in biological processes (B); active transport; muscle contraction; nerve transmission; synthesis; translocation; nitrogen fixation; receptors ENERGY TRANSFERS WHICH TAKE PLACE INSIDE LIVING ORGANISMS
Living organisms including all plants and animals require energy for their cellular processes. In biological processes, the immediate energy source is often in the form adenosine triphosphate (ATP). The nucleotide ATP maintains both catabolic and anabolic reactions. An example of a catabolic reaction is respiration where large molecules are broken down into smaller ones with energy released. An example of an anabolic reaction is photosynthesis where small molecules are built up into larger ones using energy. ATP is built up from ADP and inorganic phosphate ions (3-4 PO, abbreviated to Pi) by condensation and is then hydrolysed by the enzyme ATPase to ADP and Pi to release energy that can be used for energy requiring reactions such as photosynthesis in plants.
Plants are able to produce ATP during the light dependent reaction of photosynthesis in the thylakoid of the chloroplast. Red and blue wavelengths of light are absorbed by chlorophyll in chloroplasts on Photosystem II. The chloroplasts are protected and contained by a membrane, but they are close to the surface of the cell to catch the maximum amount of light. Their broad length also allows larger wavelengths of light to be absorbed. The energy absorbed is transferred to electrons and excites them to a higher energy level. This leads to the photolysis of water which results in the formation of hydrogen ions, electrons and oxygen gas. The electrons formed during photolysis then replace those excited by the light. The excited electrons are then passed along the electron transport chain in a series of redox reactions from one carrier to the next. The energy released by this passage is used to activate ATPase to combine ADP and Pi to form ATP. This process of converting ADP to ATP using...
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