Bioenergetics - Group 5 PDF

:  2. How photosynthetic organism capture light energy to form sugar molecure photosynthetic organisms capture light energy to excite electrons, which are used to generate ATP and NADPH. These molecules then power the Calvin Cycle, where CO₂ is fixed into sug...

:  2. How photosynthetic organism capture light energy to form sugar molecure photosynthetic organisms capture light energy to excite electrons, which are used to generate ATP and NADPH. These molecules then power the Calvin Cycle, where CO₂ is fixed into sugars like glucose. Here are the explanations on how it works.  1. Light Absorption Photosynthesis begins when chlorophyll, a green pigment in the chloroplasts, absorbs light energy (mostly from the blue and red wavelengths of sunlight). This absorbed energy excites electrons in the chlorophyll molecules, raising them to a higher energy state.  2. Water Splitting (Photolysis) The energy from light also helps split water molecules (H₂O) into oxygen (O₂), protons (H⁺), and electrons. This occurs in the thylakoid membrane during the light- dependent reactions. Oxygen is released as a byproduct, while the electrons and protons are used in the next stages of photosynthesis.  3. Electron Transport Chain (ETC) The excited electrons move through a series of proteins embedded in the thylakoid membrane known as the electron transport chain (ETC). As electrons travel through the ETC, they lose energy, which is used to pump protons into the thylakoid space, creating a proton gradient.  4. ATP and NADPH Formation The proton gradient drives the production of ATP (adenosine triphosphate) through a process called chemiosmosis, facilitated by an enzyme called ATP synthase. The electrons, after passing through the ETC, are transferred to NADP⁺ to form NADPH. Both ATP and NADPH are energy carriers needed for the next stage of photosynthesis. 5. Carbon Fixation (Calvin Cycle) In the second stage of photosynthesis (light- independent reactions), ATP and NADPH are used to convert carbon dioxide (CO₂) into glucose, a simple sugar. This process, known as the Calvin Cycle, occurs in the stroma of the chloroplasts. It involves the enzyme RuBisCO, which helps fix CO₂ into a stable organic molecule. 6. Formation of Glucose Through a series of reactions in the Calvin Cycle, the carbon atoms from CO₂ are used to form glucose (C₆H₁₂O₆), which the plant can use as an energy source or store for later use.  3. How organisms obtain and utilize energy? Organisms acquire energy by two general methods: by light or by chemical oxidation. Productive organisms, called autotrophs, convert light or chemicals into energy-rich organic compounds beginning with energy-poor carbon dioxide (CO2). These autotrophs provide energy for the other organisms, the heterotrophs. Organisms obtain energy from the food they consume. The food consumed by the organisms undergo cellular respiration as a result of which energy is released.MMitochondria are called power houses of the cells.