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WineEast Grapegrowing OAK ALTERNATIVES - BECOPAD Eastern Distributor for Beco Filter Sheets, Siha Yeast, EvOAK Oak Alternatives, Parker-dh Membranes, Chillers, N2 Generators, Zander Air Products R CENTRIFUGES 76 W in e s & V i ne s J U NE 2 013 - DECAN T E S TERILE FILTRATION - WATER FILTRATIO N - SIHA YEAST - Vines 'work' for energy transfer I f you think back to high school biology class, photosynthesis is the one entropy-reducing reaction in our world. Entropy reduction happens when photons convert to electrons, and the electrons are converted into sugars that create the energy required to grow plants. Entropy is the tendency toward disorder, and as it decreases, higher energy products such as sugars and other carbohydrates, proteins and fats are created. Photosynthetic reactions capture and store energy from our sun for future use. Plants accomplish this feat by utilizing the pigment compounds in their leaves to capture the photons from the sun and funnel the photons striking the plant's leaf to a point where, for all intents and purposes, the photons "charge a battery" in the chloroplast. Once the "battery" is charged, it can then transfer this energy to a "motor" that performs work for us. In the case of the grapevine, the work done is growing the vine and producing its fruit for us to harvest. The capturing light of—and producing energy-rich compounds in—a plant are divided into the light reaction and the dark reaction (or light-independent reactions) of photosynthesis. The critical aspect of this set of reactions is the timing and location in the plant where they occur. The light reaction obviously happens in the chloroplasts, Light where a pigment-based antenna is laid out to capture light. Cartenoids In Figure 1 at right, the photons are captured by the antenna, Cartenoids b Antenna which transfers their energy to the reaction center at bottom complexes Chlorophyll a of the antenna. This transfer charges the "battery" by forming Reaction compounds such as ATP and NADPH, which have a higher center energy state than their ground state counterparts ADP and Figure 1: Chloroplast's NADP+. Notice in Figure 1 that there are different pigmented pigment arrangement capcompounds listed. Each one of these compounds absorbs tures various wavelengths of light. After being different wavelengths of light. The broader the spectrum of captured, each pigment electromagnetic energy the chloroplast absorbs, the more 'hands off' electrons to the efficient the plant is at harvesting the sun's energy. next molecule until the electron is transferred to Once produced, these energy-rich compounds must then the reaction center. migrate to the energy transfer point in the leaf and release their energy to drive the light-independent reactions or dark reaction in the chloroplast stoma to convert carbon dioxide into glucose through a complex series of reactions that all first-year biology students learn as the Calvin Benson cycle. All of these reactions occur in the plant structure called the thylakoid membrane, which is located in the chloroplast of the grape leaf. Figure 2 (at right) presents a more global, three-dimensional view of the chloroplast. There are Plant Cell Chloroplast Structure pigmented structures on the thylakoid membrane Outer membrane that absorb the photon, transferring its energy from Inner membrane one pigment to another, down the energy gradient to the reaction center in the thylakoid membrane. Here Stroma Lamellae Thylakoid Stroma is where the electron energy is converted into ATP Intermembrane space and NADPH, raising the chloroplasts energy state. Granum (Stack The light reactions on the thylakoid membrane of Thylakoids) all happen in a microsecond. The energy-rich Figure 2: The Thylakoid, Granum and compounds that have been produced must then Stroma create space for the chloromigrate to the stroma, where the dark reactions plast, which is surrounded by a series occur via the Calvin Benson cycle. From the of membranes. logistics of operation you can get a perspective for the time delay between the light reactions and the dark reactions because of the structural arrangement of the reaction sites in the fixation of carbon dioxide. R.C.