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Question : What is chemiosomosis ? Describe the role of chemiosmosis in generation of ATP. |
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Answer» Solution :1. Chemiosmosis : The movement of ions across a selectively permeable membrane down their electrochemical gradient is called chemiosmosis. 2. Role of chemiosmosis in generation of ATP : (1) Chemiosmosis plays an IMPORTANT role in gnertation of ATP during respiration and phostosynthesis. (2) During respiration, the ATP is generated in mitochondria while in photosynthesisit is generated in chloroplasts. (3) In both these processes, the generation of ATP occurs byt the movement of hydrogen ions across a membrane. 4. In photosynthesis,the movement of hydrogen ions occurs through thylakoid imembrane leading to the accumulation of protons (hydrogen ions) in their lumen. (5) When hydrogen ions (protons) diffuse from an area of higher concentration of protons to an area of lower concentration of protons, an electrochemical concentration gradient of protons is established. (6) According to Dr Peter Mitchell who proposed the chemiosmotic hypothesis, the electrochemical concentration gradient of protons is responsible for the synthesis of ATP under the influence of the enzyme ATP synthase by the PROCESS of chemiosmosis. (7) It is BELIEVED that DUE to the splitting of water molecules on the innerside of the thylakoid membrane protons (hydrogen ions) accumolate within the lumen of the thylakoids. (8) The NADP reductase enzyme is located on the stroma side of the membrane. (9) Along with the electrons that come from ferredoxin, protons are required for the reduction of NADP to `NADPH_(2)` . Therefore,protons decrease in the stroma and increase in the lumen of the thylakoid. (10) Owing to this a proton gradient is established across the thylakoid mimbrane. This results in spontaneousmovement of protons generating energy which is utilized for the synthesis of ATP. |
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