BIOL 1103 Test 3 Notes

BIOL 1103 Test 3 Notes - PHOTOSYNTHESIS the process by...

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PHOTOSYNTHESIS : the process by which certain groups of organisms capture energy from sunlight and convert this solar energy into chemical energy that is initially stored in a carbohydrate Energy poor reactants + solar energy energy rich products (C6H12O6) o This is the source of all food and all oxygen The higher the light intensity, the greater the change in O 2 All steps of photosynthesis occur in the thylakoid membranes (where light is absorbed) and the stroma o Chlorophyll a- primary pigment active in plant photosynthesis The power of the sun is used to boost the energy of electrons that are derived from water and bring them together with both a low-energy sugar and carbon dioxide from the atmosphere, thus producing an energy-rich carbohydrate meaning food. Photosynthesis can be divided into 2 major sets of steps. In the first set, known as the light reactions, absorbed solar energy moves electrons derived from water in 2 ways: 1) Physically to a molecule called a electron acceptor 2) metaphorically to a higher energy state o The energy acquired in the light reaction stakes 2 forms: energetic electrons stored in the carrier NADH and energy stored in the energy transfer molecule ATP . An important by-product of the light reactions is the oxygen produced when water is split. o Why is the light reaction so important? The splitting of water: electrons and oxygen The transformation of solar energy to chemical energy Production of ATP Calvin Cycle-the set of steps in photosynthesis in which energetic electrons are brought together with carbon dioxide and a sugar to produce an energetic carbohydrate o An energy poor sugar is brought together with carbon dioxide from the atmosphere and the resulting product is energized with electrons derived from the light reactions. The ATP produced in the light reactions powers this process. o Input: CO 2 , ATP, and electrons (contained in hydrogen atoms) from NADH o Output: energized sugar (G3P) that may be used for food or part of the plant’s structure
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Carbon Cycle Atmosphere [730],increasing 3.2 + 0.2/yr Land : Plants [500] Soil [1500] Sink 0.7 + 0.8/yr Ocean : [38,000] Sink 2.4 + 0.7/yr Fossil fuels: 6.3 ± 048/year Land-use: 2.2 ± 0.8/year Residual Sink 2.9 + 1.1/yr * Largest Sink=OCEAN Higher Concentrations may improve plant growth Some of the C assimilated in plants is released as CO2 to the atmosphere through respiration. C is transferred to the soil by root exudates. Dead roots within the soil decompose via the soil food chain and are converted into soil organic matter. To increase C sequestration in trees the amount of C allocated to trunks and large branches must be increased or the trees must live longer C that is allocated to leaves and fine roots is recycled to the atmosphere too quickly to be an effective C sink Factors that could diminish the effect of CO2 fertilization on forest growth: 1. potential for N availability to restrict the ability of forests to sustain CO2 induced
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BIOL 1103 Test 3 Notes - PHOTOSYNTHESIS the process by...

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